Contents for CyberSky Help

Welcome

Legal Information

Registration

Procedures

Commands

Explorations

Glossary

Diagrams

Tables

Product Support


Contents for CyberSky Help (Welcome)
Contents for CyberSky Help

Welcome

Description of CyberSky

Hardware and Software Requirements

Installing CyberSky

Uninstalling CyberSky

Configuration

Understanding the Display

Legal Information

Registration

Procedures

Commands

Explorations

Glossary

Diagrams

Tables

Product Support


Contents for CyberSky Help (Legal Information)
Contents for CyberSky Help

Welcome

Legal Information

Copyright

License

Disclaimer

Trademarks

Registration

Procedures

Commands

Explorations

Glossary

Diagrams

Tables

Product Support


Contents for CyberSky Help (Registration)
Contents for CyberSky Help

Welcome

Legal Information

Registration

Definition of Shareware

Registering CyberSky

Registration Methods

Procedures

Commands

Explorations

Glossary

Diagrams

Tables

Product Support


Contents for CyberSky Help (Procedures)
Contents for CyberSky Help

Welcome

Legal Information

Registration

Procedures

Viewing and Printing the Display

Using the Location Database

Customizing the Display

Commands

Explorations

Glossary

Diagrams

Tables

Product Support


Contents for CyberSky Help (Commands)
Contents for CyberSky Help

Welcome

Legal Information

Registration

Procedures

Commands

File Menu

Options Menu

Time Menu

Animation Menu

View Menu

Help Menu

Explorations

Glossary

Diagrams

Tables

Product Support


Contents for CyberSky Help (Explorations)
Contents for CyberSky Help

Welcome

Legal Information

Registration

Procedures

Commands

Explorations

General

Time

Stars

Sun

Planets

Glossary

Diagrams

Tables

Product Support


Contents for CyberSky Help (Glossary)
Contents for CyberSky Help

Welcome

Legal Information

Registration

Procedures

Commands

Explorations

Glossary

Glossary

Diagrams

Tables

Product Support


Contents for CyberSky Help (Diagrams)
Contents for CyberSky Help

Welcome

Legal Information

Registration

Procedures

Commands

Explorations

Glossary

Diagrams

Diagram 1—Solar and Sidereal Time

Diagram 2—Orbits

Diagram 3—Retrograde Motion

Tables

Product Support


Contents for CyberSky Help (Tables)
Contents for CyberSky Help

Welcome

Legal Information

Registration

Procedures

Commands

Explorations

Glossary

Diagrams

Tables

Table 1—Greek Alphabet

Table 2—Constellations

Table 3—Spectral Types

Table 4—Luminosity Classes

Table 5—Physical Data

Table 6—Orbital Data

Table 7—Units of Distance

Product Support


Contents for CyberSky Help (Product Support)
Contents for CyberSky Help

Welcome

Legal Information

Registration

Procedures

Commands

Explorations

Glossary

Diagrams

Tables

Product Support

Upgrades

Reporting Bugs

Contacting the Author


Description of CyberSky

CyberSky™ is a colorful, easy-to-use program that transforms your computer screen into a planetarium, allowing you to learn about astronomy by exploring the sky in the past, present, and future. CyberSky can truly be thought of as a desktop planetarium, because it duplicates the features of a traditional planetarium on your computer screen. CyberSky provides a superb, innovative, and motivating learning environment. It places the sky under your control.

One of CyberSky’s most powerful and educational features is its ability to animate the display, allowing you to see animations of the changing appearance of the sky over time. Many of the most basic and interesting astronomical phenomena can only be observed over days or months of time, or by observing the sky in the distant past or future. CyberSky compresses these time spans into minutes, thereby allowing you to learn things about astronomy that previously would have required days or weeks of stargazing or a trip to a planetarium to learn.

CyberSky allows you to

View the positions of the sun, moon, and all planets of the solar system in the sky. Information about those objects, such as their distances from the earth and their rising and setting times are available by simply clicking on them with the right mouse button.

View 5080 stars. Information about those stars, such as their Bayer and Flamsteed designations, magnitudes, spectral types, and rising and setting times are available by simply clicking on them with the right mouse button. Proper names are available for 248 of the brightest stars.

View constellation lines for all 88 constellations.

Display reference lines such as the ecliptic, celestial equator, galactic equator, and equatorial coordinate system grid.

Display the north and south poles of the ecliptic, equatorial, and galactic coordinate systems.

Choose to view the sky from any location on the earth between the years 4000 BC and 4000 AD.

Understand the dynamics of the sky by performing the steps in the Explorations section of this help file. You will be able to learn about such topics as precession of the equinoxes, proper motion, and retrograde motion of planets not by reading a description but by watching CyberSky’s simulated sky.

Learn astronomical terminology by reading through this help file’s extensive glossary section.

Print the display in either black on white or in color to create your own star charts you can use to identify stars, constellations, and planets in the night sky.

If you have an interest in astronomy, CyberSky will provide hours of fun and education for you and your family.


Hardware and Software Requirements

CyberSky works with most personal computers available today. If you are running Windows 3.1 on your computer you should have no trouble running CyberSky.

The shareware version of CyberSky was designed to be installed and run on a computer system that meets the following minimum hardware and software requirements.

Hardware

Personal computer using an Intel i386, i486, Pentium, or compatible processor.

4 MB RAM.

Hard disk with about 1.5 MB free space. The registered version requires about 4.5 MB for a full installation.

One 3.5-inch high-density diskette drive.

Monitor and video adapter compatible with Windows 3.1 or higher.

Microsoft Mouse or compatible pointing device. It is impossible to use all the features of CyberSky using the keyboard alone.

Software

Microsoft MS-DOS 3.1 or later.

Microsoft Windows 3.1 or later running in 386 Enhanced mode, or Microsoft Windows for Workgroups 3.1 or later, or Windows 95, or Windows NT.


Installing CyberSky

The shareware version of CyberSky 1.0d is distributed as a compressed file named CYBERSKY.ZIP or CYBSKY1D.ZIP. You must first uncompress this file into an empty temporary directory on your hard disk. You can use PKWARE’s PKZIP 2.04g utility or any compatible utility such as WinZip to do this.

The following installation instructions assume you are using the Windows Program Manager. If you are using a Program Manager replacement such as the Norton Desktop for Windows or PC Tools for Windows, perform equivalent steps to install CyberSky.

IMPORTANT: If a previous version of CyberSky is installed on your system I recommend uninstalling the old version before installing the new version.

To install CyberSky for use on your computer system

1	Start Windows if you are not already running Windows.

2	Choose Run... from the File menu.

3	Type C:\DIR\INSTALL.EXE where C is the drive letter of your hard drive and \DIR is the directory into which you unzipped the distribution file.

If you are installing CyberSky on a networked Windows system, you must type C:\DIR\INSTALL.EXE /N instead.

4	Choose the OK button and follow the installation program’s instructions.

After CyberSky has been successfully installed, be sure to save the distribution file on your hard disk or on a diskette. You will need this file if you want to reinstall CyberSky or want to uninstall it.

If successful, the CyberSky installation program installed the following files on your hard disk in the directory you specified.

CYBERSKY.EXE	Executable file

CYBERSKY.HLP	Help file in Windows Help format

HISTORY.HLP	Version history file in Windows Help format

README.TXT	Text file containing a description of the CyberSky program, hardware and software requirements, installation instructions, and instructions on how to contact the author

VENDOR.TXT	Text file containing information for software vendors

FILE_ID.DIZ	Standard description file used by BBSs

INSTALL.LOG	Text file created during installation containing a record of the installation

BSC600B.DAT	Star data file

LOCATION.DAT	Location data file

ELEMENTS.DAT	Planets data file

ZODIAC.DAT	Zodiac constellation lines file

MAJOR.DAT	Major constellation lines file

MINOR.DAT	Minor constellation lines file

The installation program checked for the presence of the following file in your Windows system directory. If this file was present, or if your system contained an older version of this file than the one supplied by CyberSky, this file was copied to your Windows system directory.

CTL3D.DLL	Gives a 3D appearance to all CyberSky dialog boxes

If you choose the /N switch to install CyberSky on a networked Windows system, the CTL3D.DLL file was copied to your Windows directory instead.


Unnstalling CyberSky
Uninstalling CyberSky

If you have decided to remove CyberSky from your system, an uninstallation program is provided to make this job easy for you. The uninstallation program was not installed with the rest of the CyberSky files but exists in the distribution file.

The following installation instructions assume you are using the Windows Program Manager. If you are using a Program Manager replacement such as the Norton Desktop for Windows or PC Tools for Windows, perform equivalent steps to uninstall CyberSky.

To uninstall CyberSky from your computer system

1	Start Windows if you are not already running Windows

2	Uncompress the distribution file into an empty directory as you did when you installed CyberSky.

3	Choose Run... from the File menu

4	Type C:\DIR\UNINSTAL.EXE where C is the drive letter of your hard drive and \DIR is the directory into which you unzipped the distribution file.

5	Choose the OK button and follow the uninstallation program’s instructions.

6	Delete the temporary directory into which you unzipped the distribution file.

The uninstallation program will completely eliminate CyberSky from your system. It will delete the CyberSky files from the directory in which you installed CyberSky. It will also remove the CyberSky Program Manager group, if you chose to create one during installation.

You can also choose to manually uninstall CyberSky.

To manually uninstall CyberSky from your computer system

1	Start Windows if you are not already running Windows.

2	Delete the directory into which you installed CyberSky, usually C:\CYBERSKY.

3	Delete the file CYBERSKY.INI from the Windows directory.

4	Delete the CyberSky group from Program Manager.


Configuration

Before you can use CyberSky to view accurate displays of the sky, you must first configure the program.

Location

In order for CyberSky to display the sky correctly, it must know the location on the earth from which you are viewing the sky. This necessary location data includes the location’s name, latitude, longitude, and time zone.

1	Select the Location command on the Options menu. This will display the Location dialog box.

2	In the Location dialog box, simply scroll through the list of location names and find a location that is close to where you are using CyberSky.

CyberSky contains a large location database that stores the latitudes, longitudes, and time zones of all the locations you see in the list. You can view and edit this data by choosing the Edit buttons after choosing a location from the list.

3	Choose the OK button to exit the Location dialog box and return to the display. The location you selected will be used until you change it.

Daylight-Saving Time

Something else that CyberSky needs to know to produce accurate sky displays is whether daylight-saving time is in effect. CyberSky will use the time zone value for your location, plus the state of daylight-saving time to convert your computer’s system time into universal time (UT), also known as Greenwich Mean Time (GMT). Universal time is used for all internal calculations.

1.	Select the Date and Time command on the Time menu. This will display the Date and Time dialog box.

2.	If daylight-saving time is in effect, check the Daylight-Saving Time option. If it is not in effect, clear the option. The daylight-saving time state you selected will be used until you change it.

That’s it! Provided that your computer’s system date and time are correct, CyberSky will now produce accurate sky displays.


Understanding the Display

Picture yourself lying on your back at a location far away from buildings, mountains, or trees, and looking straight up at a cloudless sky. CyberSky shows you the sky from this perspective. The circle you see in the display represents the entire sky. The circumference of the circle is the horizon, and the center of the circle is the zenith, the point directly over your head.

By default the display is oriented so that the south horizon is at the bottom of the window, the north horizon is at the top, the east horizon is toward the left, and the west horizon is toward the right. You can use the Orientation command on the Options menu to change the display orientation.

Stars are represented in the display by symbols such as ovals, circles, plus signs, and dots. Larger symbols represent brighter stars and smaller symbols represent dimmer stars. Stars that are categorized in the four brightest levels are by default displayed in colors based on their B - V color indices. These colors include Deep Sky Blue, Cyan, White, Pale Yellow, Gold, Orange, and Light Pink. Dimmer stars are displayed in white and levels of gray.

You can use the Stars command on the Options menu to specify the dimmest stars that should be included in the display, and whether stars should be displayed in color or in white only.

Simply click on a star symbol with the right mouse button to view the Star Data dialog box. This dialog box displays the star’s proper name, Bayer letter, Flamsteed number, constellation, equatorial coordinates, magnitude, color index, spectral type, and rising, transit, and setting times. Use the dialog box’s Help button or look through the Glossary section of this help file to find out what these terms mean.

Constellations, categorized as zodiac, major, and minor constellations, are represented by lines connecting stars in the display. In some cases the constellation lines do a remarkably good job of suggesting the outline of an animal or mythological figure for which the constellation is named. In other cases, especially for very small constellations in the southern skies, you will find that constellation lines are nothing more than lines drawn between the two or three brightest stars in that constellation.

Constellations are not labeled in the display. If you want to identify a constellation, simply click on a star that is part of the constellation with the right mouse button. The Star Data dialog box will appear and will display which constellation that star is part of.

Zodiac, major, and minor constellations can be turned on or off using the View command on the Options menu. The colors used to display constellation lines can be customized using the Colors command on the Options menu.

The sun is represented in the display by a yellow circle the same size as the full moon. Please understand that the sun is not shown to scale, but is enlarged to be more easily distinguishable from bright stars.

Simply click on the sun symbol with the right mouse button to view the Sun Data dialog box. This dialog box displays the sun’s equatorial and ecliptic coordinates, distance, angular diameter, magnitude, and rising, transit, and setting times. Use the dialog box’s Help button or look through the Glossary section of this help file to find out what these terms mean.

The moon is represented in the display by a symbol that approximates the appearance of the moon in its correct phase. The illuminated portion of the lunar disk is always displayed in white, and the dark portion is always displayed in dark gray. Please understand that the moon is not shown to scale, but is enlarged to more easily display the phase.

Simply click on the moon symbol with the right mouse button to view the Moon Data dialog box. This dialog box displays the moon’s equatorial and ecliptic coordinates, distance, angular diameter, illumination, and rising, transit, and setting times. Use the dialog box’s Help button or look through the Glossary section of this help file to find out what these terms mean. This dialog box also displays an enlarged view of the moon symbol allowing you to see the phase better.

Planets are represented in the display by their traditional symbols. Look at the legend on the right side of the display for help on identifying the planets.

The planets Mercury, Venus, Mars, Jupiter, and Saturn are visible without optical aid. The planets Uranus, Neptune, and Pluto are included in the display for completeness, but please understand that these planets are only visible with the aid of good binoculars or a telescope.

Simply click on a planet symbol with the right mouse button to view the Planet Data dialog box. This dialog box displays the planet’s equatorial and ecliptic coordinates, elongation from the sun, distance, angular diameter, illumination, magnitude, and rising, transit, and setting times. Use the dialog box’s Help button or look through the Glossary section of this help file to find out what these terms mean. This dialog box also displays an enlarged view of the planet’s disk allowing you to see the phase better.

The colors used to display the planet symbols can be customized using the Colors command on the Options menu.

Reference lines such as the ecliptic, celestial equator, and galactic equator are represented in the display by lines of different colors. The north and south poles of the ecliptic, equatorial, and galactic coordinate systems are displayed as plus signs in the same colors used for the reference lines.

Coordinates of the equatorial coordinate system, right ascension and declination, are represented by a grid of lines in the display. Lines of right ascension are displayed every hour of right ascension. Lines of declination are displayed every ten degrees of declination. The number of lines displayed is reduced near the north and south celestial poles.


Context Help Command

Use the Context Help command to obtain help on some portion of CyberSky. When you choose the Context Help command using one of the shortcuts listed below, the mouse pointer will change to an arrow and question mark.

After the cursor changes into this context help cursor, click somewhere in the CyberSky window, such as a toolbar button. The help topic will be shown for the item you clicked.

Shortcuts

Toolbar

Keyboard	Shift+F1


Title Bar

The title bar is located along the top of a window. It contains the name of the application window.

To move the window, drag the title bar. Note: You can also move dialog boxes by dragging their title bars.

A title bar may contain the following elements:

Application control-menu button

Document control-menu button

Maximize button

Minimize button

Name of the application

Name of the document

Restore button


Toolbar

The toolbar is displayed across the top of the application’s window, below the menu bar. The toolbar provides quick mouse access to some of the commands used in CyberSky. To hide or display the toolbar, choose the Toolbar command from the View menu.

See Also

Toolbar Options dialog box


Status Bar

The status bar is displayed across the bottom of the application’s window. The status bar displays descriptions reminding you of what menu commands and toolbar buttons do. To hide or display the status bar, choose the Status Bar command from the View menu.

See Also

Toolbar Options dialog box


System Menu Size Command
Size Command

Use the Size command on the System menu to allow you to size the active window with the keyboard’s arrow keys. After you choose the Size command the cursor will change to a four-headed arrow.

After the cursor changes into this four-headed arrow, use the following instructions to size the active window.

To size the active window

1	Press one of the arrow keys (left, right, up, or down arrow key) to move the cursor to the border you want to move.

2	Press an arrow key to move the border.

3	Press the Enter key when the window is the size you want.

Note: This command is unavailable if you maximize the window.

Shortcuts

Mouse	Drag the size bars at the corners or edges of the window.


System Menu Move Command
Move Command

Use the Move command on the Control menu to allow you to move the active window with the keyboard’s arrow keys. After you choose the Move command the cursor will change to a four-headed arrow.

After the cursor changes into this four-headed arrow, use the following instructions to move the active window.

To move the active window

1	Press one of the arrow keys (left, right, up, or down arrow key) to move the window to the location you want to move it.

2	Press the Enter key when the window is the positioned where you want it.

Note: This command is unavailable if you maximize the window.

Shortcuts

Keyboard	Ctrl+F7


System Menu Minimize Command
Minimize Command

Use the Minimize command on the application’s Control menu to reduce the CyberSky window to an icon.

Shortcuts

Mouse	Click the minimize button on the application’s title bar in Windows 3.x.

Click the minimize button on the application’s title bar in Windows 95.

Keyboard	Alt+F9


System Menu Maximize Command
Maximize Command

Use the Maximize command on the application’s Control menu to enlarge the CyberSky window to fill the available screen space.

Shortcuts

Mouse	Click the maximize button on the application’s title bar; or double-click the title bar itself in Windows 3.x.

Click the maximize button on the application’s title bar; or double-click the title bar itself in Windows 95.

Keyboard	Ctrl+F10 enlarges a document window.


System Menu Close Command
Close Command

Use the Close command on a window’s Control menu to close the window.

Shortcuts

Mouse	Double-click the application window’s Control-menu box in Windows 3.x.

Click the application window’s Close button in Windows 95, or.

Double-click the application window’s small icon in the title bar in Windows 95.

Keyboard	Alt-F4


System Menu Restore Command
Restore Command

Use the Restore command on a window’s Control menu to return the window to its size and position before you chose the Maximize or Minimize command.


Task List
Switch to Command

Use the Switch to command on the application’s Control menu to display a list of all open applications.

Shortcuts

Keys:	Ctrl+Esc


No Help Available

No help is available.


No Help Available

No help is available.


Copyright

The following legal copyright statement applies to the CyberSky application and all its supporting files.

Copyright © 1995 Stephen Michael Schimpf. All rights reserved.


License

The shareware version of CyberSky is provided at no charge to the user for evaluation. You are encouraged to pass a copy of the shareware version of CyberSky along to your friends for evaluation. Please encourage them to register their copy if they find that they can use it.

The essence of "user-supported" software is to provide personal computer users with quality software without high prices, and yet to provide incentive for programmers to continue to develop new products.

If you find this program useful and find that you are using CyberSky and continue to use CyberSky after a trial period of 30 days, you must make a registration payment of US$ 21.00, plus a shipping and handling charge of US$ 3.00 in North America or US$ 4.00 elsewhere, to Stephen Michael Schimpf. The registration payment will license one copy for use on any one computer at any one time. You must treat this software just like a book. An example is that this software may be used by any number of people and may be freely moved from one computer location to another, so long as there is no possibility of it being used at one location while it's being used at another. Just as a book cannot be read by two different persons at the same time.

Commercial users of CyberSky must register and pay for their copies of CyberSky within 30 days of first use or their license is withdrawn. Site-license arrangements may be made by contacting Stephen Michael Schimpf.

Anyone distributing CyberSky for any kind of remuneration must first contact Stephen Michael Schimpf using one of the methods listed under Product Support for authorization.

You may not modify, translate, reverse engineer, decompile, disassemble (except to the extent applicable laws specifically prohibit such restriction), or create derivative works based on CyberSky; copy CyberSky (except for back-up purposes); rent, lease, transfer or otherwise transfer rights to CyberSky; or remove any proprietary notices or labels on CyberSky.

Title, ownership rights, and intellectual property rights in and to CyberSky shall remain in Stephen Michael Schimpf. CyberSky is protected by the copyright laws of the United States and international copyright treaties. Title, ownership rights, and intellectual property rights in and to the content accessed through CyberSky is the property of the applicable content owner and may be protected by applicable copyright or other law. This license gives you no rights to such content.

This license will terminate automatically if you fail to comply with the limitations described above.


Disclaimer

USERS OF CYBERSKY MUST ACCEPT THE FOLLOWING DISCLAIMER OF WARRANTY. BY USING THIS SOFTWARE YOU ARE CONSENTING TO BE BOUND BY AND ARE BECOMING A PARTY TO THIS AGREEMENT.

CYBERSKY IS SUPPLIED “AS IS”. STEPHEN MICHAEL SCHIMPF DISCLAIMS ALL WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION, THE WARRANTIES OF MERCHANTABILITY AND OF FITNESS FOR ANY PURPOSE. STEPHEN MICHAEL SCHIMPF ASSUMES NO LIABILITY FOR DAMAGES, DIRECT OR CONSEQUENTIAL, WHICH MAY RESULT FROM THE USE OF CYBERSKY.

UNDER NO CIRCUMSTANCES AND UNDER NO LEGAL THEORY, TORT, CONTRACT, OR OTHERWISE, SHALL STEPHEN MICHAEL SCHIMPF OR HIS SUPPLIERS OR RESELLERS BE LIABLE TO YOU OR ANY OTHER PERSON FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OF ANY CHARACTER INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF GOODWILL, WORK STOPPAGE, COMPUTER FAILURE OR MALFUNCTION, OR ANY AND ALL OTHER COMMERCIAL DAMAGES OR LOSSES. IN NO EVENT WILL STEPHEN MICHAEL SCHIMPF BE LIABLE FOR ANY DAMAGES IN EXCESS OF STEPHEN MICHAEL SCHIMPF'S LIST PRICE FOR A LICENSE TO CYBERSKY, EVEN IF STEPHEN MICHAEL SCHIMPF SHALL HAVE BEEN INFORMED OF THE POSSIBILITY OF SUCH DAMAGES, OR FOR ANY CLAIM BY ANY OTHER PARTY. THIS LIMITATION OF LIABILITY SHALL NOT APPLY TO LIABILITY FOR DEATH OR PERSONAL INJURY TO THE EXTENT APPLICABLE LAW PROHIBITS SUCH LIMITATION. FURTHERMORE, SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF INCIDENTAL OR CONSEQUENTIAL DAMAGES, SO THIS LIMITATION AND EXCLUSION MAY NOT APPLY TO YOU.


Trademarks

CyberSky is a trademark of Stephen Michael Schimpf.

Microsoft, MS, and MS-DOS are registered trademarks and Visual C++, Windows, Windows 95, and Windows NT is trademarks of Microsoft Corporation.

Intel is a registered trademark and Pentium is a trademark of Intel Corporation.

CompuServe is a registered trademark of CompuServe, Inc.

PKWARE, PKZIP, and PKUNZIP are registered trademarks of PKWARE, Inc.

Apple, Macintosh, and Mac are registered trademarks of Apple Computer, Inc.

Trademarks of other companies mentioned in this documentation appear for identification purposes only and are the property of their respective companies.


Definition of Shareware

Shareware distribution gives users a chance to try software before buying it. If you try a shareware program and continue using it, you are expected to register. Individual programs differ on details—some request registration while others require it, some specify a maximum trial period. With registration, you get anything from the simple right to continue using the software to an updated program with printed manual.

Copyright laws apply to both shareware and commercial software, and the copyright holder retains all rights, with a few specific exceptions as stated below. Shareware authors are accomplished programmers, just like commercial authors, and the programs are of comparable quality. In both cases, there are good programs and bad ones. The main difference is in the method of distribution. The author specifically grants the right to copy and distribute the software, either to all and sundry or to a specific group. For example, some authors require written permission before a commercial disk vendor may copy their shareware.

Shareware is a distribution method, not a type of software. You should find software that suits your needs and pocketbook, whether it's commercial or shareware. The shareware system makes fitting your needs easier, because you can try before you buy. And because the overhead is low, prices are low also. Shareware has the ultimate money-back guarantee—if you don't use the product, you don't pay for it.


Registering CyberSky

CyberSky is marketed as a shareware application. Please understand that this version of CyberSky is not free. You are licensed to evaluate CyberSky for a period of 30 days. If you wish to continue to use CyberSky after this initial trial period, you must purchase a registered copy. The registered version of CyberSky costs US$ 21.00, plus a shipping and handling charge of US$ 3.00 in North America or US$ 4.00 elsewhere.

What You Will Receive

Three 3.5-inch high-density diskettes containing the latest registered version of CyberSky plus approximately 30 cool images of the sun, moon, planets, and other bodies of the solar system that can be displayed from within the program.

Confidence that the software you are purchasing is useful to you and works with your hardware and software.

Product support. If you experience problems with CyberSky, you can use any of a number of methods to contact me, and I will try to solve the problem to your satisfaction. If I cannot do this, and it is within 60 days of your purchase of CyberSky, I will refund your money minus the shipping and handling charge.

Notification when future versions of CyberSky become available. CyberSky will be improved and enhanced, and versions specifically for Windows 95 and Windows NT will be available.

Discounts on all future versions of CyberSky. Registered users will be able to purchase upgrades for a very reasonable fee.

My gratitude. Writing software takes years of experience, a substantial investment in development tools, and a lot of time. Your registration means a lot to me, and helps support a small business, one based on honesty and trust.

See the following topic, Registration Methods, for instructions on how to order your registered version of CyberSky!

CyberSky has great potential for use by educational institutions. If you are interested in purchasing multiple copies of this application, please contact me for information about volume discounts. If you are interested in a site license allowing you to run a copy of CyberSky on all computers at your location, please contact me. Use one of the methods listed under Product Support.


Registration Methods

Please use any of the following methods, whichever one is most convenient for you, to order the registered version of CyberSky.

Registering via Mail

Registering via CompuServe

Registering via Credit Card


CyberSky Registration Form

Please choose the Print Topic command from the File menu to print this registration form.

Payment

To order the latest registered version of CyberSky, fill out this form and enclose a check or money order for one of the following amounts. These prices include shipping and handling.

United States of America, Canada, and Mexico	US$ 24.00

Central America and South America	US$ 25.00

Europe, Africa, and the Middle East	US$ 25.00

Asia, Australia, and New Zealand	US$ 25.00

Please make checks or money orders payable in US funds to “Stephen Michael Schimpf".

Required Information

Name

Street

City	State/Province

ZIP/Postal Code	Country

Optional Information

E-mail Address

Where did you obtain CyberSky 1.0d?

Please write any comments and suggestions about features you would like to see in future versions of CyberSky on the back of this page.

Please mail this completed form along with payment to the following address.

Stephen Michael Schimpf

2444 West 230th Street

Torrance, CA 90501–5242

United States of America

Thank you for your order!


Registering via CompuServe

CompuServe provides an easy and convenient online shareware registration service. To register CyberSky through CompuServe you must have a CompuServe account. The cost of the registered version of CyberSky, US$ 21.00, plus a shipping and handling charge of US$ 3.00 in North America or US$ 4.00 elsewhere, will be billed directly to your CompuServe account.

To register CyberSky via CompuServe

1	Connect to CompuServe.

2	GO SWREG.

3	Search for registration ID 6128 or search for program title “CyberSky”.

4	Follow the instructions to place your order.

Any questions about the status of the shipment of the order, refunds, registration options, product details, technical support, volume discounts, dealer pricing, site licenses, etc., must be directed to one of the addresses or telephone numbers listed under Product Support.

CompuServe will notify me the day of your order and I will ship your registered copy of CyberSky within two business days of your order.

Thank you for your order!


Registering via Credit Card

You can register CyberSky by calling PsL, the Public (software) Library. This established organization takes credit card orders for shareware authors, at no extra cost to you. The following instructions on how to use their service are provided by PsL. Please follow them closely.

CREDIT CARD ORDERS ONLY

You can order with MasterCard, Visa, American Express, or Discover from the Public (software) Library by using one of the following telephone numbers or e-mail addresses.

Toll free	800–2424–PsL (800–242–4775)

Telephone	713–524–6394

Fax	713–524–6398

CompuServe	71355,470

Internet	71355.470@compuserve.com

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Viewing and Printing the Display

This section contains procedures for viewing and printing the display, and for obtaining information about objects in the display.

Which procedure are you interested in learning about?

Printing the Display

Setting the Date and Time

Animation

Viewing Object Data


Printing the Display

CyberSky can produce a printed version of the display. CyberSky produces black on white output on most printers, and full-color output matching the screen on color printers.

To print the display

1	Choose the Print Setup command on the File menu to display the Print Setup dialog box.

2	Specify the printer, page orientation, and any other appropriate options. The printed display will be easiest to read and use if you specify landscape orientation.

3	Choose the OK button or press the Enter key to return to the display.

4	Choose the Print command on the File menu to display the Print dialog box.

5	Specify the print quality, number of copies, and any other appropriate options.

6	Choose the OK button to print the display.

See Also

Print dialog box

Print Setup dialog box


Setting the Date and Time

CyberSky can display the sky for any date and time between the years 4000 BC and 4000 AD, inclusive.

To set the date and time

1	Choose the Date and Time command on the Time menu to display the Date and Time dialog box.

2	Specify the local date in the Date box. Select the month from the list of month names, and then type in the day of the month in the range 1 to 28, 29, 30, or 31. Then type in the year in the range 1 to 4000. Specify whether the year you typed is BC or AD.

3	Specify the local time in the Time box. Type in the hours, minutes, and seconds.

4	Check the option in the DST group to specify that daylight-saving time is in effect.

5	Choose the OK button or press the Enter key to return to the display. The display will be redrawn to reflect the new date and time.

To quickly increment or decrement the date or time

1	Choose the Subtract Hour, Add Hour, Subtract Day, Add Day, Subtract Week, or Add Week command on the Time menu.

2	Repeat step 1 until you have reached the desired date and time.

See Also

Date and Time dialog box

Toolbar


Animation

CyberSky can animate the display, allowing you to see an animation of the changing appearance of the sky over time. This is one of CyberSky’s most powerful features, as it lets you learn things about astronomy that previously would have required days or weeks of stargazing or a trip to a planetarium to learn.

To run an animation

1	Choose the Time Step command on the Animation menu to display the Time Step dialog box.

2	Specify the time step between successive animation frames and then choose the OK button to return to the display.

3	Choose either the Forward or Reverse command on the Animation menu to start animation with time moving forward or in reverse.

4	When you are finished viewing the display choose the Stop command on the Animation menu. While animation is occurring this is the only command available.

See Also

Time Step dialog box

Toolbar


Viewing Object Data

CyberSky can display information about the stars, sun, moon, and planets in the display. This information includes equatorial and ecliptic coordinates, distances, magnitudes, rising, transit, and setting times, and much more.

To view data for an object in the display

1	Simply click on the object with the right mouse button. This will display the Star Data, Sun Data, Moon Data, or Planet Data dialog box.

2	When you are finished viewing data for the object, choose the OK button to return to the display.

See Also

Star Data dialog box

Sun Data dialog box

Moon Data dialog box

Planet Data dialog box


Using the Location Database

This section contains procedures for using the Location and Edit Location dialog boxes to add, delete, or edit a location in CyberSky’s location database. The location database initially contains information about over 600 locations on the earth, and you are free to add or delete locations, or to edit the data for existing locations.

Which procedure are you interested in learning about?

Adding a Location

Deleting a Location

Editing a Location


Adding a Location

CyberSky allows you to add locations to the database.

To add a location to the database

1	Choose the Location command on the Options menu to display the Location dialog box.

2	Choose the Add button in the Location dialog box to display the Edit Location dialog box.

3	Type the name of the location in the Location box, in a format such as Country: City, State. The name should be no more than 64 characters long.

4	Type the latitude in decimal degrees in the Latitude box. Select North or South for this latitude. Do not use a minus sign to indicate south latitude.

5	Type the longitude in decimal degrees in the Longitude box. Select East or West for this longitude. Do not use a minus sign to indicate west longitude.

6	Type the time zone in decimal hours in the Time Zone box. The time zone is the difference between local time and universal time for that time zone. Select Ahead or Behind for this time zone to indicate whether the time zone is ahead or behind universal time. Do not use a minus sign to indicate hours behind universal time.

7	Choose the OK button or press the Enter key to return to the Location dialog box.

See Also

Location dialog box

Edit Location dialog box


Deleting a Location

CyberSky allows you to delete one or more locations from the database.

To delete a location from the database

1	Choose the Location command on the Options menu to display the Location dialog box.

2	Select a location from the list in the Location box.

3	Choose the Delete button. A Confirmation dialog box will appear asking you to confirm that you want to delete the location. Choose the OK button in the Confirmation dialog box to delete the location.

4	Choose the OK button or press the Enter key to return to the Location dialog box.

See Also

Location dialog box

Edit Location dialog box

Confirmation dialog box


Editing a Location

CyberSky allows you to edit the data associated with a location in the database.

To edit a location in the database

1	Choose the Location command on the Options menu to display the Location dialog box.

2	Choose the Add button in the Location dialog box to display the Edit Location dialog box.

3	Modify the name of the location in the Location box, in a format such as Country: City, State. The name should be no more than 64 characters long.

4	Modify the latitude in decimal degrees in the Latitude box. Select North or South for this latitude. Do not use a minus sign to indicate south latitude.

5	Modify the longitude in decimal degrees in the Longitude box. Select East or West for this longitude. Do not use a minus sign to indicate west longitude.

6	Modify the time zone in decimal hours in the Time Zone box. The time zone is the difference between local time and universal time for that time zone. Select Ahead or Behind for this time zone to indicate whether the time zone is ahead or behind universal time. Do not use a minus sign to indicate hours behind universal time.

7	Choose the OK button or press the Enter key to return to the Location dialog box.

See Also

Location dialog box

Edit Location dialog box


Customizing the Display

This section contains procedures for customizing features of CyberSky that affect the appearance of the display.

Which procedure are you interested in learning about?

Customizing the Location

Customizing the View

Customizing the Stars

Customizing the Orientation

Customizing the Colors


Customizing the Location

CyberSky can display the sky as seen from any location on the earth. Normally you will set up CyberSky to display the sky as seen from your location. If you choose to learn more about astronomy using the Explorations section of this help file you will need to set the location to the North Pole, South Pole, and to the Equator.

To customize the location

1	Choose the Location command on the Options menu to display the Location dialog box.

2	Select a location from the list in the Location box.

3	Choose the OK button or press the Enter key to return to the display. The display will be redrawn to reflect the sky as seen from the new location.

See Also

Location dialog box


Customizing the View

CyberSky allows you to turn on or off the display of celestial objects and reference lines and poles. The objects include the stars, sun, moon, and planets. The constellation lines include zodiac, major, and minor constellations. The reference lines include the ecliptic, celestial equator, galactic equator, and equatorial coordinate system grid lines. The reference poles include the north and south poles of the ecliptic, equatorial, and galactic coordinate systems.

To customize the view

1	Choose the View command on the Options menu to display the View dialog box.

2	Specify which objects you want displayed in the Objects group.

3	Specify which constellation lines you want displayed in the Constellations group.

4	Specify which reference lines you want displayed in the Lines group.

5	Specify which north/south poles you want displayed in the North/South Poles group.

6	Choose the OK button or press the Enter key to return to the display. The display will be redrawn to reflect any changes you made in the dialog box.

See Also

View dialog box

Toolbar


Customizing the Stars

CyberSky allows you to customize the stars displayed based on their brightness, and allows you to specify whether bright stars should be drawn in color or in white only. You can specify the brightness of the dimmest stars displayed between 3rd and 6th magnitude. Stars of the 6th magnitude are the dimmest stars you would be able to see without optical aid in a dark location far from city lights.

To customize the stars

1	Choose the Stars command on the Options menu to display the Stars dialog box.

2	Specify the magnitude of the dimmest stars displayed by moving the slider in the Limiting Magnitude box to reach a desired value between 3.0 and 6.0.

3	Check the Display Brightest Stars in Color option if you want bright stars in the display to be drawn using color rather than in white only.

4	Choose the OK button or press the Enter key to return to the display. The display will be redrawn to reflect the new limiting magnitude and color choice.

See Also

Stars dialog box


Customizing the Orientation

CyberSky allows you to customize the display orientation so that the north, northeast, east, southeast, south, southwest, west, or northwest horizon is positioned at the bottom of the display.

To customize the orientation

1	Choose the Orientation command on the Options menu to display the Orientation dialog box.

2	Specify the compass direction you want positioned at the bottom of the display using the radio buttons in the Horizons group.

3	Choose the OK button or press the Enter key to return to the display. The display will be redrawn to reflect the new orientation.

See Also

Orientation dialog box


Customizing the Colors

CyberSky allows you to customize the colors used for most of the elements of the display.

To customize colors

1	Choose the Colors command on the Options menu to display the Colors dialog box.

2	Select an element of the display and then choose the Select button. Or simply double-click on the element in the list.

3	Use the common Color dialog box to specify a color.

4	Choose the OK button to return to the Colors dialog box.

5	Repeat steps 2 through 4 to customize other colors.

6	Choose the OK button to return to the display. The display will be redrawn to reflect the color choices you made.

CyberSky allows you to reset any color to its default value after you have customized it.

To restore a default color

1	Choose the Colors command on the Options menu to display the Colors dialog box.

2	Select an element of the display and then choose the Reset button.

3	Choose the OK button to return to the display. The display will be redrawn to reflect the color choices you made.

CyberSky allows you to reset all colors to their default values.

To restore all default colors

1	Choose the Colors command on the Options menu to display the Colors dialog box.

2	Choose the Reset All button.

3	Choose the OK button to return to the display. The display will be redrawn to reflect the color choices you made.

See Also

Colors dialog box


File Menu

These topics provide information about commands on the application’s File menu.

Which command would you like to learn about?

Print

Print Preview

Print Setup

Exit


Print Command

Use the Print command on the File menu to print the display. When you use this command the Print dialog box will appear to allow you to specify printing options.

Shortcuts

Toolbar

Keyboard	Ctrl+P

See Also

Print dialog box


Print Preview Command

Use the Print Preview command on the File menu to preview any printed display. When you choose this command the CyberSky window will be replaced by the print preview window.

Shortcuts

Toolbar

See Also

Print Setup dialog box


Print Setup Command

Use the Print Setup command on the File menu to specify printing options. When you choose this command the Print Setup dialog box will appear to allow you to specify printer options.

See Also

Print Setup dialog box


Exit Command

Use the Exit command on the File menu to exit your CyberSky session. You can also use the Close command on the application’s control menu.

Note that when you exit CyberSky some of your preferences—for example, whether to display the brightest stars in color, or whether to display the equatorial coordinate system grid—will be saved. These values will be the default values used the next time you start CyberSky.

Shortcuts

Mouse	Double-click the application window’s Control-menu box in Windows 3.x.

Click the application window’s Close button in Windows 95.

Double-click the application window’s small icon in the title bar in Windows 95.

Keyboard	Alt-F4

See Also

Close Command


Options Menu

These topics provide information about commands on the application’s Options menu.

Which command would you like to learn about?

Location

View

Stars

Orientation

Colors

Screen Font

Printer Font


Location Command

Use the Location command on the Options menu to specify the location from which the sky is being viewed.

See Also

Location dialog box


View Command

Use the View command on the Options menu to specify which objects and reference lines are to be included in the display.

See Also

View dialog box


Stars Command

Use the Stars command on the Options menu to set options related to the stars in the display.

See Also

Stars dialog box


Orientation Command

Use the Orientation command on the Options menu to set the orientation of the display.

See Also

Orientation dialog box


Colors Command

Use the Colors command on the Options menu to customize the colors used in the display.

See Also

Colors dialog box


Screen Font Command

Use the Screen Font command on the Options menu to specify which font should be used in the display.

See Also

Font dialog box


Printer Font Command

Use the Printer Font command on the Options menu to specify which font should be used in the printed display.

See Also

Font dialog box


Time Menu

These topics provide information about commands on the application’s Time menu.

Which command would you like to learn about?

Date and Time

Subtract Hour

Add Hour

Subtract Day

Add Day

Subtract Week

Add Week


Date and Time Command

Use the Date and Time command on the Time menu to set the date and time. This command displays the Date and Time dialog box.

Shortcuts

Toolbar

See Also

Date and Time dialog box


Subtract Hour Command

Use the Subtract Hour command on the Time menu to subtract one hour from the time.

Shortcuts

Toolbar


Add Hour Command

Use the Add Hour command on the Time menu to add one hour to the time.

Shortcuts

Toolbar


Subtract Day Command

Use the Subtract Day command on the Time menu to subtract one day from the date.

Shortcuts

Toolbar


Add Day Command

Use the Add Day command on the Time menu to add one day to the date.

Shortcuts

Toolbar


Subtract Week Command

Use the Subtract Week command on the Time menu to subtract one week to the date.

Shortcuts

Toolbar


Add Week Command

Use the Add Week command on the Time menu to add one week to the date.

Shortcuts

Toolbar


Animation Menu

These topics provide information about commands on the application’s Animation menu.

Which command would you like to learn about?

Forward

Reverse

Stop

Time Step


Forward Command

Use the Forward command on the Animation menu to start animation with time moving forward. While animation is occurring, the only command that is available is Stop.

Shortcuts

Toolbar

See Also

Time Step dialog box


Reverse Command

Use the Reverse command on the Animation menu to start animation with time moving in reverse. While animation is occurring, the only command that is available is Stop.

Shortcuts

Toolbar

See Also

Time Step dialog box


Stop Command

Use the Stop command on the Animation menu to stop animation. While animation is occurring, this is the only command available. If you wish to change some display options, you must do so when animation is turned off.

Shortcuts

Toolbar


Time Step Command

Use the Time Step command on the Animation menu to set the simulation time that passes between each animation step. This command displays the Time Step dialog box.

See Also

Time Step dialog box


View Menu

These topics provide information about commands on the application’s View menu.

Which command would you like to learn about?

Toolbar

Status Bar

Toolbar Options


Toolbar Command

Use the Toolbar command on the View menu to turn the display of the application’s toolbar on or off. A check mark will appear next to this command when the toolbar is being displayed.

See Also

Toolbar Options dialog box

Toolbar


Status Bar Command

Use the Status Bar command on the View menu to turn the display of the application’s status bar on or off. A check mark will appear next to this command when the status bar is being displayed.

See Also

Toolbar Options dialog box

Status Bar


Toolbar Options Command

Use the Toolbar Options command on the View menu to specify toolbar options.

Shortcuts

Toolbar

See Also

Toolbar Options dialog box

Toolbar


Help Menu

These topics provide information about commands on the application’s Help menu.

Which command would you like to learn about?

Contents

Search for Help On

How to Use Help

About CyberSky


Contents Command

Use the Contents command on the Help menu to display the contents page for CyberSky help in the Windows Help application.

Remember that you can chose the Contents button in Windows Help at any time to return to this starting point.

Shortcuts

Toolbar

Keyboard	F1


Search for Help On Command

Use the Search for Help On command on the Help menu to search for a keyword in CyberSky help.


How to Use Help Command

Use the How to Use Help command on the Help menu to view instructions for using the Windows Help application.


About CyberSky Command

Use the About CyberSky command on the Help menu to display information about the version of CyberSky you are using.

See Also

About CyberSky dialog box


General Explorations

The explorations in this section are suggestions for ways to use CyberSky to learn more about astronomy in general.

Each exploration includes a short introduction and a list of steps you need to perform. You may find it useful to look up some of the terms used in the Glossary section of this help file.

Each exploration involves animation and should be performed with only the stars, sun, moon, and planets included in the display, unless otherwise instructed. The display orientation should also be set so that the south horizon is at the bottom of the window.

Which exploration are you interested in?

Watch the Sky at the North Pole

Watch the Sky at the South Pole

Watch the Sky at the Equator


Watch the Sky at the North Pole

In this exploration you will watch the sky at the North Pole.

Perform these steps

1	Set the location to the North Pole using the Location command on the Options menu.

2	Display the ecliptic and celestial equator using the View command on the Options menu.

3	Set the animation time step to 30 minutes using the Time Step command on the Animation menu.

4	Choose the Forward command on the Animation menu to start animation.

You should now see the stars move in the display. Watch their motion for a minute or so. Notice anything interesting? The stars are moving counterclockwise in circles around the sky. None of them are rising or setting.

The star directly in the center of the display is α Ursae Minoris, better know as Polaris or simply the North Star. The center of the display is the zenith, the point directly above your head, so if you were at the North Pole and looked straight up, you would see the North Star.

At the North Pole the celestial equator is found at the horizon. If you look carefully you will see this line. You will also see the part of the ecliptic that is north of the celestial equator. The ecliptic is the line along which the sun moves.

Perform these steps

1	Choose the Stop command on the Animation menu to stop animation.

2	Set the animation time step to seven solar days using the Time Step command on the Animation menu.

3	Choose the Forward command on the Animation menu to start animation.

After watching the display for a minute or two you should notice that the sun spends half a year below the horizon and half a year above the horizon. This illustrates why the North Pole has six months of day and six months of night.

Because the North Pole and South Pole are at opposite ends of the earth, when it is day at the North Pole, it is night at the South Pole, and vice versa.


Watch the Sky at the South Pole

In this exploration you will watch the sky at the South Pole.

Perform these steps

1	Set the location to the South Pole using the Location command on the Options menu.

2	Display the ecliptic and celestial equator using the View command on the Options menu.

3	Set the animation time step to 30 minutes using the Time Step command on the Animation menu.

4	Choose the Forward command on the Animation menu to start animation.

You should now see the stars move in the display. Watch their motion for a minute or so. Notice anything interesting? The stars are moving clockwise in circles around the sky. None of them are rising or setting.

The center of the display is the zenith, the point directly above your head. Notice that there is no bright star near the center of the display. The southern sky does not have an equivalent to the North Star in the northern sky.

At the South Pole the celestial equator is found at the horizon. If you look carefully you will see this line. You will also see the part of the ecliptic that is south of the celestial equator. The ecliptic is the line along which the sun moves.

Perform these steps

1	Choose the Stop command on the Animation menu to stop animation.

2	Set the animation time step to seven solar days using the Time Step command on the Animation menu.

3	Choose the Forward command on the Animation menu to start animation.

After watching the display for a minute or two you should notice that the sun spends half a year below the horizon and half a year above the horizon. This illustrates why the South Pole has six months of day and six months of night.

Because the North Pole and South Pole are at opposite sides of the earth, when it is day at the North Pole, it is night at the South Pole, and vice versa.


Watch the Sky at the Equator

In this exploration you will watch the sky at the equator.

Perform these steps

1	Set the location to the Equator using the Location command on the Options menu.

2	Display the ecliptic and celestial equator using the View command on the Options menu.

3	Set the animation time step to 30 minutes using the Time Step command on the Animation menu.

4	Choose the Forward command on the Animation menu to start animation.

You should now see the stars move in the display. Watch their motion for a minute or so. Notice anything interesting? The stars are rising on the east side of the sky and are setting on the west side of the sky. Each star rises and sets.

The celestial equator crosses the sky from due east to due west and passes directly overhead. This makes sense because the celestial equator is just the projection of the earth’s equator onto the celestial sphere, and you are watching the sky from the earth’s equator.

The position of the ecliptic line depends on the time of year. The ecliptic crosses the celestial equator in two places at opposite sides of the sky. The ecliptic reaches a maximum angular distance from the celestial equator of 23.5°, which is the inclination of the earth’s axis of rotation with respect to the plane of its orbit around the sun.

Notice that the sun, moon, and planets are never very far from the ecliptic. The ecliptic is defined as the intersection of the plane of the earth’s orbit around the sun and the celestial sphere. The planes of the orbits of the other planets in the solar system are roughly similar to that of the earth, and so all objects of the solar system will appear close to the ecliptic.


Time Explorations

The explorations in this section are suggestions for ways to use CyberSky to learn more about time.

Each exploration includes a short introduction and a list of steps you need to perform. You may find it useful to look up some of the terms used in the Glossary section of this help file.

Each exploration involves animation and should be performed with only the stars, sun, moon, and planets included in the display unless otherwise instructed. The display orientation should also be set so that the south horizon is at the bottom of the window.

Which exploration are you interested in?

Solar and Sidereal Time


Solar and Sidereal Time

In this exploration you will learn about the difference between solar and sidereal time.

Perform these steps

1	Set the time to 12:00 noon using the Date and Time command on the Time menu.

2	Set the animation time step to one solar day using the Time Step command on the Animation menu.

3	Choose the Forward command on the Animation menu to start animation.

Watch the display for a little while. The time step between animation frames is one solar day, which is the length of time it takes the earth to rotate once so that it has the same orientation with respect to the sun. Notice that whereas the sun remains stationary in the sky, the stars move slowly from east to west day after day.

Perform these steps

1	Choose the Stop command on the Animation menu to stop animation.

2	Set the animation time step to one sidereal day using the Time Step command on the Animation menu.

3	Choose the Forward command on the Animation menu to start animation.

Watch the display for a little while. The time step between animation frames is now one sidereal day, which is the length of time it takes the earth to rotate once so that it has the same orientation with respect to the stars. The stars now remain stationary in the sky, but the sun moves slowly from west to east day after day.

Why is there a difference between solar and sidereal time? It takes 23h 56m 4s for the earth to rotate once with respect to the stars. During this time the earth has also moved along its orbit around the sun. Because the direction of the sun has changed, it takes the earth 3 m 56s more to rotate once with respect to the sun, for a total of exactly 24 hours.

See Also

Diagram 1—Solar and Sidereal Time Diagram


Stars Explorations

The explorations in this section are suggestions for ways to use CyberSky to learn more about how the coordinates of stars and their positions change over time.

Each exploration includes a short introduction and a list of steps you need to perform. You may find it useful to look up some of the terms used in the Glossary section of this help file.

Each exploration involves animation and should be performed with only the stars, sun, moon, and planets included in the display, unless otherwise instructed. The display orientation should also be set so that the south horizon is at the bottom of the window.

Which exploration are you interested in?

Precession

Proper Motion


Precession

In this exploration you will observe the effect of precession.

The earth is not a perfect sphere, but has an equatorial diameter that is slightly larger than its polar diameter. The sun, moon, and other planets of the solar system exert a gravitational attraction on the equatorial bulge of the earth. It is this force that is responsible for precession.

The positions of the celestial poles actually move across the sky, tracing out circles with a diameter of about 47° on the celestial sphere every 25,800 years. Therefore, the pole star observed thousands of years ago was not the star we see near the north celestial pole today.

The star we call the North Star was not near the celestial pole thousands of years in the past, and will not be near the pole thousands of years in the future. Currently the north pole of the earth’s axis of rotation points toward the star α Ursae Minoris, better known as Polaris or simply the North Star.

Precession does not alter the constellation outlines or change their boundaries with respect to the stars, but causes a slow drift of the entire celestial coordinate system on the celestial sphere. This drift is called precession of the equinoxes.

You should be familiar with the motion of the stars around the North Star. If not, carry out the Watch the Sky at the North Pole exploration.

Perform these steps

1	Set the location to the North Pole using the Location command on the Options menu.

2	Display the ecliptic and celestial equator using the View command on the Options menu.

3	Set the year to 2700 BC using the Date and Time command on the Time menu.

4	Set the animation time step to 30 minutes using the Time Step command on the Animation menu.

5	Choose the Forward command on the Animation menu to start animation.

Watch the motion of the stars in the display. You will find that the stars no longer move around α Ursae Minoris. The star we call the North Star was not at the north celestial pole in 2700 BC.

Try to identify the star that is closest to the north celestial pole. Remember that at the North Pole the north celestial pole is directly overhead, in other words at the center of the display. Click on the star closest to the center of the display with the right mouse button. The Star Data dialog box will appear, telling you that the pole star back when the Egyptians were building the great pyramids was α Draconis, also known as Thuban!


Proper Motion

In this exploration you will observe the effect of proper motion.

Perform these steps

1	Set the location to the North Pole using the Location command on the Options menu.

2	Display the zodiac, major, and minor constellations using the View command on the Options menu.

The star at the center of the display is Polaris, the North Star. It is located at the end of the handle of the Little Dipper, part of the constellation Ursa Minor. Not far from the Little Dipper you should be able to find the Big Dipper, part of the constellation Ursa Major.

Follow the curve of the handle of the Big Dipper and you will be guided toward a star called Arcturus, the brightest star in the constellation Bootes. When you have found Arcturus, take note of its location with respect to the lines of the constellation Bootes. Arcturus lies at the point where two lines meet.

Perform these steps

1	Set the year to 4000 BC using the Date and Time command on the Time menu.

When the display is redrawn you will find that everything has moved. If you have performed the previous exploration, Precession, you will know that this is due to the precession of the equinoxes. Polaris is no longer at the center of the display. Nevertheless, you should be able to find the Little Dipper, Big Dipper, and Bootes in the new display.

When you have found Bootes in the display, you will see that Arcturus is no longer located where it was with respect to the constellation lines.

When you change the date and time, CyberSky calculates the effects of precession on the stars and constellation lines, and then calculates the effect of proper motion on the stars. This allows you to see that stars do move across the sky with respect to other stars and references like constellation lines.

All stars move through space, just as our sun does, but those stars that are close to our solar system appear to move much faster than those stars that are farther away. Even the closest stars outside the solar system are very far away, and detecting proper motion takes large telescopes and very sensitive equipment. This exploration shows that the effects of proper motion do accumulate over thousands of years so that you can notice it.

Proper motion was first discovered by the English astronomer Halley when he noticed that Arcturus was not at the same location it was shown at in star charts made 2000 years earlier by the Greek scholar Hipparchus.


Sun Explorations

The explorations in this section are suggestions for ways to use CyberSky to learn more about the motion of the sun across the sky over time.

Each exploration includes a short introduction and a list of steps you need to perform. You may find it useful to look up some of the terms used in the Glossary section of this help file.

Each exploration involves animation and should be performed with only the stars, sun, moon, and planets included in the display, unless otherwise instructed. The display orientation should also be set so that the south horizon is at the bottom of the window.

Which exploration are you interested in?

Analemma


Analemma

On a globe or a map of the earth you will sometimes see an elongated figure-eight drawn on the surface of the earth. This figure, called an analemma, represents the position of the sun over the course of one year. The vertical part of the figure is due to the sun’s changing declination, and the horizontal part is due to the equation of time, the difference between true solar time and mean solar time.

In this exploration you will be able to see a similar figure traced out by the motion of the sun in the sky over the course of one year.

Perform these steps

1	Set the time to 12:00 noon and turn daylight-saving time off using the Date and Time command on the Time menu.

2	Set the animation time step to seven solar days using the Time Step command on the Animation menu.

3	Choose the Forward command on the Animation menu to start animation.

Watch the motion of the sun in the sky. Each animation step shows the sun at noon. Over the course of one year you will see the sun move farther and farther south, reach a minimum declination, move farther and farther north, reach a maximum declination, and then move south again. Notice that the sun is not exactly on the meridian at noon, but is sometimes east and sometimes west of the meridian at noon. This is what causes the sun to trace out a figure-eight rather than simply move north and south along a vertical line.

The position of the sun at the points farthest north and south on the analemma correspond to the summer and winter solstices. The point at the center of the figure-eight corresponds to the vernal and autumnal equinoxes.


Planets Explorations

The explorations in this section are suggestions for ways to use CyberSky to learn more about the motions of the planets of the solar system across the sky over time.

Each exploration includes a short introduction and a list of steps you need to perform. You may find it useful to look up some of the terms used in the Glossary section of this help file.

Each exploration involves animation and should be performed with only the stars, sun, moon, and planets included in the display unless otherwise instructed. The display orientation should also be set so that the south horizon is at the bottom of the window.

Which exploration are you interested in?

Retrograde Motion of an Inferior Planet

Retrograde Motion of a Superior Planet


Retrograde Motion of an Inferior Planet

In this exploration you will observe the retrograde motion of the planet Mercury.

The orbit of Mercury around the sun lies inside the earth’s orbit. The earth moves slower in its orbit than does Mercury, and at some part of their motion around the sun Mercury will move past the earth.

Perform these steps

1	Set the date to May 1, 1995 AD and the time to 12:00 noon using the Date and Time command on the Time menu.

2	Display the ecliptic using the View command on the Options menu. This will make it easier to find and track Mercury because planets are always found near the ecliptic.

3	Set the animation time step to one sidereal day using the Time Step command on the Animation menu. This will keep the stars fixed in the display and allow you to watch Mercury move against the background stars.

Find Mercury in the display. Look at the symbol in the legend if you need help identifying Mercury. You should find Mercury near the center of the display between the moon and the sun. Notice that Mercury is very close to the ecliptic.

Perform these steps

1	Choose the Forward command on the Animation menu to start animation.

Watch Mercury move along the ecliptic. By the last week of May you will see Mercury slow down in its direct motion. Over the next few weeks you will see Mercury moving backwards along the ecliptic. By the middle of June Mercury will again be slowing down over the Hyades asterism, the V-shaped group of stars in the constellation Taurus. By July it will again be moving forward along the ecliptic.

See Also

Diagram 3—Retrograde Motion


Retrograde Motion of a Superior Planet

In this exploration you will observe the retrograde motion of the planet Mars.

The orbit of Mars around the sun lies outside the earth’s orbit. The earth moves faster in its orbit than does Mars, and at some part of their motion around the sun the earth will move past Mars. This happens when Mars is near opposition.

Imagine driving in a car, and passing another car. The other car will appear to be moving backwards in relation to your car. Similarly, viewed against the background stars, Mars will appear to move backwards in relation to its normal or direct motion.

Perform these steps

1	Set the date to October 1, 1996 AD and the time to 8:00 using the Date and Time command on the Time menu.

2	Display the ecliptic using the View command on the Options menu. This will make it easier to find and track Mars because planets are always found near the ecliptic.

3	Set the animation time step to seven sidereal days using the Time Step command on the Animation menu. This will keep the stars fixed in the display and allow you to watch Mars move against the background stars.

Find Mars in the display. Look at the symbol in the legend if you need help identifying Mars. You should find Mars near the center of the display between the constellations Leo and Cancer. Notice that Mars is very close to the ecliptic.

Perform these steps

1	Choose the Forward command on the Animation menu to start animation.

Watch Mars move along the ecliptic. By February you will see Mars slow down in its direct motion. Over the next three months you will see Mars moving backwards along the ecliptic in the constellation Virgo. By April Mars will again be slowing down, and by May it will again be moving forward along the ecliptic.

See Also

Diagram 3—Retrograde Motion


Glossary

Click the first letter of the word you want to look up.

A

Absolute Magnitude

Albedo

Altitude

Analemma

Ångstrom

Angular Diameter

Angular Measure

Apparent Magnitude

Apparent Sun

Asterism

Asteroid

Astrometry

Astronomical Twilight

Astronomical Unit

Astronomy

Astrophysics

Atmospheric Refraction

Aurora

Autumnal Equinox

Azimuth

B

Bayer Letter

Binary Star

Bolide

C

Cardinal Points

Celestial Equator

Celestial Mechanics

Celestial Meridian

Celestial Poles

Celestial Sphere

Circumpolar

Civil Twilight

Color Index

Comet

Conjunction

Constellation

Cosmogeny

Cosmos

Cosmology

Crescent

Cusp

D

Declination

Density

Direct Motion

Distance

Double Star

E

Eclipse

Ecliptic

Ecliptic Coordinate System

Ecliptic Latitude

Ecliptic Longitude

Elongation

Ephemeris

Epoch

Equation of Time

Equatorial Coordinate System

Equinox

Evening Star

F

Fireball

First Quarter

Flamsteed Number

Full

G

Galactic Coordinate System

Galactic Equator

Galactic Latitude

Galactic Longitude

Galilean Satellites

Gibbous

Great Circle

H

Harvest Moon

Horizon Coordinate System

Hour Angle

Hour Circle

Hunter’s Moon

I

Illumination

Inclination

Inferior Conjunction

Inferior Planet

Inner Planet

J

Julian Date

L

Last Quarter

Latitude

Light-year

Limb

Local Sidereal Time

Longitude

Luminosity

M

Magnitude

Mass

Mean Sun

Meridian

Meteor

Meteoroid

Meteorite

Meteor Shower

Milky Way

Morning Star

N

Nadir

Nautical Twilight

New

North Star

O

Occultation

Opposition

Orbit

Outer Planet

P

Parallax

Parsec

Planet

Pole Star

Precession

Proper Motion

Proper Name

Q

Quadrature

R

Retrograde Motion

Revolution

Right Ascension

Rising Time

Rotation

S

Setting Time

Sidereal Day

Sidereal Time

Solar Day

Solstice

Spectral Type

Spectrum

Star

Summer Solstice

Sun

Superior Conjunction

Superior Planet

Synodic Period

T

Terminator

Transit

Transit Time

U

Universal Time

Universe

V

Variable Star

Vernal Equinox

Vertical Circle

W

Wax

Wane

Winter Solstice

Z

Zenith

Zodiac

Zodiacal Light


Absolute Magnitude (M)

Apparent magnitude of a celestial object if it was located at a standard distance of 10 parsecs or 32.6 light-years from an observer.

The sun’s absolute magnitude is about 4.8.


Albedo

Measure of the reflecting power of the surface of a nonluminous body such as a planet, moon, or asteroid. An albedo of 1.0 represents a surface that reflects all light that strikes it whereas an albedo of 0.0 represents a surface that absorbs all light that strikes it.

The surfaces of the planet Mercury and the moon are made mostly of volcanic rock that is a poor reflector of incident light. The albedos of Mercury and the moon are 0.07 and 0.06 respectively. The surface of the earth consists largely of water and the earth’s albedo is therefore higher, about 0.36. The planet Venus as well as the giant gas planets Jupiter, Saturn, Uranus, and Neptune are shrouded in clouds that are good reflectors of light, and these bodies all have albedos above 0.5.


Altitude (h)

Angular distance of a celestial object above or below the horizon. Altitude and azimuth are coordinates in the horizon coordinate system.

Altitude is usually measured in units of degrees from 0° to 90° for altitudes above the horizon and from 0° to -90° for altitudes below the horizon.

The apparent altitude of a celestial object is affected by atmospheric refraction. CyberSky calculates this effect for objects in the display.


Ångstrom (Å)

Unit of length used in measuring the wavelength of light and other electromagnetic radiation. One Ångstrom is equal to one ten-billionth of one meter, or about the diameter of one hydrogen atom. A human hair is about 500,000 Å in diameter.


Analemma

Figure-eight pattern with one loop much larger than the other, depicting the sun’s declination and the equation of time over the course of one year.


Angular Diameter

Observed diameter of a celestial body, measured in degrees, minutes, and seconds of arc.


Angular Measure

Angles are measured in degrees (°), minutes ('), and seconds (") of arc. A full circle contains 360°, a degree contains 60', and one arc minute contains 60".

The diameters of the sun and moon are about one-half degree or about 30 arc minutes across. One arc minute is about the smallest angular measure that can be perceived by the best human eyes without optical aid. One arc second is roughly the angular measure of a typical coin seen from three miles or five kilometers away.


Apparent Magnitude (m)

Magnitude of a celestial object observed from the earth.

The apparent magnitude of a celestial object depends on its luminosity, its distance from the earth, and on the amount of light absorbed between the object and the earth.


Apparent Sun

See Mean Sun.


Asterism

Distinctive group of stars that are not one of the 88 constellations recognized by the International Astronomical Union. One example is the Big Digger, which is not itself a constellation but is part of the constellation Ursa Major.


Asteroid

One of many small bodies that orbit the sun. Most are found between the orbits of Mars and Jupiter. Asteroids are also known as minor planets.


Astrometry

Branch of astronomy concerned with the measurement of the precise positions, sizes, and motions of stars and other celestial bodies.


Astronomical Twilight

Period between the time the sun is 12° and 18° below the horizon.


Astronomical Unit (AU)

Unit of length equal to the average distance between the earth and the sun. One AU is equal to 92,955,807 miles or 149,597,870 kilometers.

The astronomical unit is mainly used for distances within the solar system. Pluto, the planet most distant from the sun, lies approximately 40 AUs from the center of the solar system. The entire solar system is therefore about 80 AUs in diameter. The nearest star outside the solar system is about 270,000 AUs from the sun, or about 7,000 times the distance of Pluto!


Astronomy

Science concerned with the study of the stars and all other bodies in the universe, the space between those bodies, and of the universe as a whole. Major branches of astronomy include astrometry, astrophysics, and celestial mechanics.


Astrophysics

Branch of astronomy concerned with the study of the physical and chemical processes associated with celestial bodies and with the space between those bodies. Astrophysics focuses in particular on the production and expenditure of energy in stars and galaxies and seeks to understand how this activity affects the evolution of such systems.


Atmospheric Refraction

Bending of the light from a celestial object as it passes through the earth’s atmosphere. Atmospheric refraction bends the light toward the earth, causing celestial objects to appear slightly higher in the sky than they really are.

The effect of atmospheric refraction depends on the altitude of the object and is greatest near the horizon. The position of an object at the horizon has been shifted by about 35 arc minutes toward the zenith, meaning that the object is really 35 arc minutes below the horizon but is visible due to atmospheric refraction.

CyberSky calculates the effect of atmospheric refraction for objects in the display.


Aurora

Glowing, often moving, display of colored light seen high in the atmosphere near the north and south magnetic poles of the earth. Auroras are caused by charged particles from the sun that become trapped in the earth’s magnetic field. High-altitude air molecules within about 20° of the magnetic poles and approximately 60 mi (100 km) high are excited by these particles and emit light.


Autumnal Equinox

Time when the sun crosses the celestial equator moving from north to south. This takes places about September 21 and marks the beginning of fall in the northern hemisphere and the beginning of spring in the southern hemisphere.


Azimuth (A)

Angular distance from the north point eastward to the intersection of the horizon and the object’s vertical circle. Altitude and azimuth are coordinates in the horizon coordinate system.

Azimuth is usually measured in units of degrees from 0° to 360°.


Bayer Letter

Letter of the Greek alphabet assigned to stars in each constellation.

This system of star names was introduced by Johann Bayer in 1603 in his book Uranometria that catalogs 1277 stars. He assigned the letter α (alpha) to the brightest star in a constellation, β (beta) to the second-brightest star, γ (gamma) to the third brightest, and so on. The letters are usually assigned in this order of brightness, but mistakes were made, so this is sometimes not the case.


Binary Star

Pair of stars that are revolving around a common center of gravity. Some components of binary stars are so close to each other that they complete one revolution in a fraction of a day. Others are so far apart that centuries pass before they complete one revolution.

The first such star was discovered by Herschel, who proved the mutual revolution of Castor in 1803. Binary and multiple stars are common in our galaxy. Perhaps about half of all stars are part of binary and multiple star systems. Binary stars are important to astronomers because observations of their orbital motions provides the only direct way to determine the masses of stars.


Bolide

Term used for a very bright meteor that explodes into fragments near the end of its path through the earth’s atmosphere.


Cardinal Points

Four principal points on the horizon, called the north point, south point, east point, and west point.


Celestial Equator

Great circle formed by projecting the earth’s equatorial plane onto the celestial sphere. The celestial equator is 90° from both the north and south celestial poles.

The axis of the earth’s daily rotation is tilted with respect to its orbital plane, and therefore the ecliptic and celestial equator are tilted with respect to each other. This angle, known as the obliquity of the ecliptic, is currently roughly 23.5°. The precession of the earth’s axis causes this angle to slowly change over time.


Celestial Mechanics

Branch of astronomy concerned with the study of the motions of celestial bodies under the influence of the force of gravity.


Celestial Meridian

Projection of the observer’s meridian on the celestial sphere. The observer’s celestial meridian passes through both celestial poles, and passes through the observer’s zenith.

The celestial meridian divides the sky into an East half and a West half. When an object in the sky is in the East half, it is rising, and when it is in the West half it is setting. When the object is on the celestial meridian, it has reached its highest point in the sky.


Celestial Poles

Projections of the north and south poles of the earth’s axis of rotation onto the celestial sphere. The precession of the earth’s axis causes the celestial poles to trace out circles on the celestial sphere in a period of about 25,800 years.

The north celestial pole is currently found near the star α Ursae Minoris, better known as Polaris or simply the North Star, in the constellation Ursa Minor. The south celestial pole is currently found in the constellation Octans.


Celestial Sphere

Sphere of immense radius centered on the earth. It provides a convenient surface on which to draw and study the motions of points in the sky as seen from an observation point on the earth. Celestial bodies may be thought of as being projected onto the surface of this immense sphere.


Circumpolar

Term used to describe stars that are permanently above the horizon at a given location on the earth. All stars with positive declinations are circumpolar at the north pole, and all stars with negative declinations are circumpolar at the south pole.


Civil Twilight

Period between the time of sunrise or sunset and the time the sun is 6° below the horizon.


Color Index

Difference between the apparent magnitude of a star measured at one standard wavelength of light and another longer wavelength. A star’s color index value depends on the distribution of light across the spectrum, and is therefore a measure of the color and temperatures of the star.

Currently, colors indices are measured using the Johnson-Morgan UBV system. The apparent magnitude of a star is measured at three wavelengths, ultraviolet (U) at 3600 Ångstroms, blue (B) at 4200 Ångstroms, and greenish-yellow (V) at 5400 Ångstroms. Subtracting these values yields the U - B and B - V color indices. The more positive the color index, the redder and cooler the star is. The more negative the color index, the bluer and hotter the star is.

CyberSky displays bright stars in colors based on their B - V color indices if that option is selected in the Stars dialog box.

        B - V < -0.2	Deep Sky Blue

-0.2 <= B - V < +0.2	Cyan

+0.2 <= B - V < +0.6	White

+0.6 <= B - V < +1.0	Pale Yellow

+1.0 <= B - V < +1.4	Gold

+1.4 <= B - V < +1.8	Orange

+1.8 <= B - V       	Light Pink


Conjunction

Moment when a planet’s elongation is 0°.

See the Diagrams section of this help file for a diagram illustrating orbital terminology.


Comet

Diffuse body of gas and solid particles that orbits the sun in an orbit generally more elliptical than that of planets. Most orbit the sun in very elongated orbits and appear at regular intervals. Others appear only once and then disappear into interstellar space, never to return.

Comets typically consist of three parts. The nucleus is usually about one mile across and is thought to resemble a dirty snowball. The coma surrounds the nucleus. The tail consists of gas and dust and appears only when the comet nears the sun. A comet’s tail always points away from the sun.


Constellation

Any one of the areas into which the sky is divided.

In ancient times constellations had no fixed limits. A constellation consisted of a group of stars that defined an outline resembling mythological persons, heroes, animals, and monsters. Ptolomy listed only 48 constellations. In more recent times more constellations were added for the areas of the southern sky that became visible to European explorers.

It became necessary to standardize the constellations and define precise boundaries separating all constellations. Just as any city on the earth falls within the boundaries of some state, province, or country, all celestial bodies fall within the boundaries of a constellation.

The International Astronomical Union established the boundaries of 88 constellations in 1930. The constellation boundaries follow arcs of right ascension and declination for the epoch 1875, January 1.


Cosmogeny

Study of the origin and evolution of the universe or one of its components, such as galaxies or the solar system.


Cosmos

Everything there is. Another term for universe.


Cosmology

Study of the structure of the universe.


Crescent

Term used to describe the appearance of a planet or moon when between zero and 50 percent of the its disk is illuminated by sunlight. In other words, when the phase of the planet or moon is between new and first quarter, or between last quarter and new.


Cusp

Pointed end of Mercury, Venus, or the moon at crescent phase.


Declination (Decl, or δ)

Angular distance of a celestial object north or south of the celestial equator. Right ascension and declination are coordinates in the equatorial coordinate system.

Declination is analogous to latitude on the earth’s surface. Declination is usually measured in units of degrees, minutes, and seconds from -90° to 90°.


Density

Mass per unit volume of a body.


Direct Motion

Apparent west to east motion of a planet as seen from the earth against the background of stars.

See the Diagrams section of this help file for a diagram illustrating direct and retrograde motion.


Distance

Separation between the earth and the sun in astronomical units, between the earth and a planet in astronomical units, or between the earth and the moon in miles or kilometers.


Double Star

Pair of stars that appear close together in the sky. Such stars may be physically close to each other and revolve around a common center of gravity, in which case they are called binary stars. Or, such stars may simply lie in the same direction in space and be otherwise unrelated to each other.


Eclipse

Total or partial obscuration of light from a celestial body as it passes through the shadow of another body. A solar eclipse is strictly an occultation.

Each year at least two and no more than five solar eclipses occur.


Ecliptic

Plane of the earth’s orbit, and the projection of that plane onto the celestial sphere. It is the line in the sky along which the sun appears to move during the course of a year. The sun moves roughly one degree along this line every day.

Because the orbits of the naked-eye planets have inclinations of seven degrees or less with respect to the ecliptic, you will always find these planets on or very close to this line.


Ecliptic Coordinate System

Coordinate system in which the fundamental reference circle is the ecliptic and the zero point is the vernal equinox. The coordinates are named ecliptic longitude (λ) and ecliptic latitude (β).


Ecliptic Latitude (β)

Angular distance of a celestial object above or below the ecliptic. Ecliptic longitude and ecliptic latitude are coordinates in the ecliptic coordinate system.

Ecliptic latitude is usually measured in units of degrees, minutes, and seconds of arc from 0° to 90° for latitudes above the ecliptic, and from 0° to -90° for latitudes below the ecliptic.


Ecliptic Longitude (λ)

Angular distance of a celestial object east of the vernal equinox. Ecliptic longitude and ecliptic latitude are coordinates in the ecliptic coordinate system.

Ecliptic longitude is usually measured in units of degrees, minutes, and seconds of arc from 0° to 360°.


Elongation

Angular distance between the sun and a planet or moon.

An object with an east elongation appears east of the sun in the evening sky, and an object with a west elongation appears west of the sun in the morning sky. An elongation of 0° is called a conjunction; one of 90° is called quadrature; and one of 180° is called opposition.

The greatest possible elongation for Mercury is about 28° and for Venus about 48°.

See the Diagrams section of this help file for a diagram illustrating orbital terminology.


Ephemeris

List of calculated positions of a celestial body or celestial bodies over successive intervals of time.


Epoch

Point of time selected as a fixed reference, especially for stellar positions or orbital elements.


Equation of Time

Difference between time based on the apparent sun and the mean sun. In other words, the difference between time as reported by a sundial and a clock. See Mean Sun.


Equatorial Coordinate System

Coordinate system in which the fundamental reference circle is the celestial equator and the zero point is the vernal equinox. The coordinates are named right ascension (α) and declination (δ).

Precession of the equinoxes causes right ascension and declination to change slowly over time. Therefore, to correctly specify the position of a celestial object, one must give not only its right ascension and declination, but also the epoch for which those coordinates apply.


Equinox

One of the two points at which the ecliptic intersects the celestial equator. This term is also applied to the moment the sun crosses such a point. See Autumnal Equinox and Vernal Equinox.


Evening Star

Term used to describe the planet Venus when it shines brightly in the western sky after sunset.


Fireball

Term used for a very bright meteor, one that far exceeds the brightness of the planet Venus. As many as 100,000 fireballs occur in the earth’s atmosphere each year.


First Quarter

Term used to describe the appearance of a planet or moon when 50 percent of the its disk is illuminated by sunlight and when the planet or moon will subsequently enter a gibbous phase.


Flamsteed Number

Number assigned to stars in each constellation.

This system of star names was introduced in 1725 by Flamsteed in his book Historia Coelestis Britannica, published posthumously. Flamsteed numbered 3,000 stars in order of right ascension within each constellation.


Full

Term used to describe the appearance of a planet or moon when its disk is fully illuminated by sunlight.


Galactic Coordinate System

Coordinate system in which the fundamental reference circle is the galactic equator and the zero point is the direction of the galactic center. The coordinates are named galactic longitude (l) and galactic latitude (b).


Galactic Equator

Plane of the Milky Way galaxy projected onto the celestial sphere. The galactic equator and the celestial equator are inclined at an angle of about 62°.


Galactic Latitude (b)

Angular distance of a celestial object above or below the galactic equator. Galactic longitude and galactic latitude are coordinates in the galactic coordinate system.

Galactic latitude is usually measured in units of degrees, minutes, and seconds of arc from 0° to 90° for latitudes above the galactic equator, and from 0° to -90° for latitudes below the galactic equator.


Galactic Longitude (l)

Angular distance of a celestial object east of the galactic center. Galactic longitude and galactic latitude are coordinates in the galactic coordinate system.

Galactic longitude is usually measured in units of degrees, minutes, and seconds of arc from 0° to 360°.


Galaxy

Large collection of gravitationally bound stars and interstellar matter. Galaxies typically are composed of hundreds of millions or billions of stars and their diameters range from a few thousand to hundreds of thousands of light-years. Many galaxies are flat disks that have a spiral appearance. Many others are elliptical and show no structural features. The rest are irregular in shape.

The galaxy that contains our solar system is a spiral galaxy called the Milky Way. It is composed of approximately 200 billion stars and is about 100,000 light-years in diameter.


Galilean Satellites

Term used to describe the four large satellites of Jupiter, discovered by Galileo.


Gibbous

Term used to describe the appearance of a planet or moon when between 50 and 100 percent of the its disk is illuminated by sunlight. In other words, when the phase of the planet or moon is between first quarter and full, or between full and last quarter.


Great Circle

Any circle on the surface of a sphere generated by a plane passing through the center of the sphere. Such a circle has the same radius as the sphere.

Lines of longitude on the surface of the earth are great circles, as are lines of declination on the celestial sphere.


Harvest Moon

Term used for the full moon closest to the autumnal equinox. The harvest moon gets its name from the fact that it rises soon after sunset, giving farmers more light and extra hours to harvest their crops.


Horizon Coordinate System

Coordinate system in which the fundamental reference circle is the horizon and the zero point is the north point. The coordinates are named altitude (h) and azimuth (A).


Hour Angle (HA, or t)

Angle measured westwards along the celestial equator from an observer’s meridian to the hour circle of a celestial body. Hour angle is usually measured in units of hours, minutes, and seconds between 0h and 24h.


Hour Circle

Any great circle on the celestial sphere along which declination is measured. A great circle passes through the celestial poles and is perpendicular to the celestial equator.


Hunter’s Moon

Term used for the first full moon following the harvest moon.


Illumination

Percentage of the visible disk of a planet or the moon that is illuminated by sunlight.


Inclination (i)

Angle between the orbital plane of a planet, satellite, asteroid, or comet and the plane of the ecliptic.


Inferior Conjunction

Moment at which the elongation of a celestial body on the near side of the sun is 0°.


Inferior Planet

Mercury or Venus. These planets lie closer to the sun than the earth.


Inner Planet

Mercury, Venus, the earth, or Mars. These planets lie closer to the sun than the main belt of asteroids found between the orbits of Mars and Jupiter.


Julian Date

Number of days that have passed since 12:00 universal time on January 1, 4713 BC. The Julian day is the number of integral days that have passed, whereas the Julian date includes the decimal fraction of the day that has elapsed since the preceding noon.

The Julian date system was invented in 1582 by the French scholar Joseph Scalinger. The Julian date is very useful because the consecutive numbering of days makes the system independent of the varying lengths of months and years. To find the number of days between two events, simply determine the Julian dates of those events and subtract one date from the other.


Last Quarter

Term used to describe the appearance of a planet or moon when 50 percent of the its disk is illuminated by sunlight and when the planet or moon will subsequently enter a crescent phase.


Latitude

Angular distance of a terrestrial location north or south of the equator. Longitude and latitude are coordinates in the terrestrial coordinate system.

Latitudes are usually measured in units of degrees, minutes, and seconds of arc from 0° to 90° for latitudes north of the equator, and from 0° to -90° for latitudes south of the equator.


Light-year (ly)

Distance that light or any other form of electromagnetic radiation travels in a vacuum at its speed of 186,200 miles per second or 300,000 kilometers per second in the course of a year.


Limb

Edge of the visible disk of the sun, moon, or any planet, or of any other celestial object that has a detectable disk.


Local Sidereal Time (LST)

Sidereal time at an observer’s location. It is equal to the right ascension currently on the observer’s celestial meridian.


Longitude

Angular distance of a terrestrial location east or west of the meridian that passes through Greenwich, England. Longitude and latitude are coordinates in the terrestrial coordinate system.

Longitude is usually measured in units of degrees, minutes, and seconds of arc from 0° to 180° for longitudes east of Greenwich, and from 0° to -180° for longitudes west of Greenwich.


Luminosity (L)

Measure of the intrinsic or absolute brightness of a star. Luminosity is equal to the total energy radiated by a star per unit time.


Magnitude

Logarithmic scale used to describe the brightness of an object. The larger the magnitude, the dimmer the object.

Magnitudes are used in astronomy for historical reasons. In ancient times the stars were ranked in six classes of magnitude. The brightest stars were assigned to the first magnitude and the faintest stars just visible to the naked eye were assigned to the sixth magnitude. CyberSky displays stars to sixth magnitude, and therefore shows all stars that you can hope to see without optical aid.

More recently, this system had to be expanded to cover stars brighter than first magnitude and fainter than sixth magnitude. In 1856 the English astronomer NR Pogson proposed that a difference of five magnitudes correspond exactly to a brightness ratio of 100 to 1. The brightness ratio of two stars that differ by one magnitude is the fifth-root of 100, or 2.512, a quantity known as the Pogson ratio. A star that is two magnitudes brighter than another star is 2.512 squared, or about 6.3, times brighter than the other star.


Mass (M)

Measure of the quantity of matter in a body, usually measured in units of grams or kilograms. Mass is also frequently measured in units of the mass of another body such as the earth or the sun. The mass of a body determines the strength of the gravitational field it produces.


Mean Sun

Reference point that moves at a uniform rate along the celestial equator and is used in timekeeping in preference to the apparent sun that moves along the ecliptic at a nonuniform rate. Clocks display time based on the mean sun.

The earth’s orbit around the sun is not a perfect circle but is an ellipse. The earth does not move along this ellipse at constant speed, but moves fastest when it is closest to the sun and slowest when it is farthest from the sun. The sun therefore moves across the background of stars at a nonuniform rate.


Meridian

Great circle on the surface of the earth that passes through both poles of the earth’s axis. In other words, an observer’s meridian is the line of longitude he or she is standing on.


Meteor

Streak of light in the sky produced by the motion of a meteoroid through the earth’s atmosphere. Meteors are typically observed 50 or 60 miles high in the atmosphere and burn up before ever getting near the ground.

On a clear, moonless night an average of about 10 meteors can be seen per hour. Much higher counts are possible during a meteor shower. The highest meteor count occurs during the early morning hours when the earth is moving into the cloud of interplanetary particles that cause meteors.

Meteors are commonly called falling stars or shooting stars.


Meteoroid

Small particle orbiting the sun in the vicinity of the earth. Most are thought to be fragments of asteroids. They are very small, about the size of a grain of sand.

It is estimated that several hundred tons of meteoroids fall on the earth each day. Almost all burn up in the atmosphere and do not strike the ground. Those that do are called meteorites.


Meteorite

Portion of a meteoroid that has survived its fall from the sky and has landed on the surface of the earth.

The stone that fell near Einsisheim, Alsace in 1492 was the first documented case of a meteorite. Meteorites were not accepted as being extraterrestrial in origin by the scientific community until 1803.


Meteor Shower

Profusion of meteors that typically fall within a day or two and appear to radiate from a common point in the sky. Meteor showers are caused by the passage of the earth through a meteor stream. Such streams are composed of the particles left behind by comets as they near the sun.


Milky Way

Galaxy that contains the solar system. The approximately 200 billion stars that compose the Milky Way galaxy are concentrated in a plane, and our view of this plane of stars from within results in the faint band of light we also call the Milky Way. It is necessary to view the sky on a clear, moonless night to see the Milky Way.


Morning Star

Term used to describe the planet Venus when it shines brightly in the eastern sky before sunrise.


Nadir

Point on the celestial sphere that lies directly beneath an observer. This point lies directly opposite the observer’s zenith and is therefore never observable.


Nautical Twilight

Period between the time the sun is 6° and 12° below the horizon.


New

Term used to describe the appearance of a planet or moon when its disk is not illuminated by sunlight.


North Star

Polaris, also known as α Ursae Minoris, or any other bright star that happens to be within a few degrees of the north celestial pole during a given era.


Occultation

Passage of a larger celestial body in front of a smaller one. A solar eclipse is strictly an occultation.


Opposition

Moment when a planet’s elongation is 180°.

See the Diagrams section of this help file for a diagram illustrating orbital terminology.


Orbit

Path along which a celestial body moves in the gravitational field of another body. For example, the path of the earth or another planet around the sun, the path of an artificial satellite around the earth, or the path of one star around another star.

Orbits are conic sections. That is, they are either ellipses, parabolas, or hyperbolas. Most orbits are ellipses, and the orbits of the planets of the solar system are almost circular. The orbits of periodic comets are ellipses.


Outer Planet

Jupiter, Saturn, Uranus, Neptune, or Pluto. These planets lie farther from the sun than the main belt of asteroids found between the orbits of Mars and Jupiter.


Parallax

Angular displacement in the apparent position of a celestial body when observed from two widely separated points.

Measuring the parallax of stars is very useful because it allows us to measure the distances to those stars. The position of a star is measured very precisely at one time, then this measurement is repeated half a year later when the earth has moved to the other side of its orbit. The star will have a slightly different position when viewed from these two perspectives, and the different in these positions allows the distance of the star to be calculated.

Bessel measured the first stellar parallax, that of 61 Cygni, in Germany in 1838.


Parsec (pc)

Unit of length equal to the distance at which the mean radius of the earth’s orbit subtends an angle of one arc second. Parsecs are used to specify the distances of objects outside our solar system, such as the distances of stars and galaxies. One parsec is equal to 206,265 astronomical units, or 3.26 light-years.


Planet

Spherical body that orbits the sun and shines only by reflected sunlight. The nine planets of the solar system are Mercury, Venus, the earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto.


Pole Star

Star closest to the north or south celestial pole at any particular time.


Precession

Periodic change in the direction of the earth’s axis of rotation. Currently the north pole of the axis of rotation points toward the star α Ursae Minoris, better known as Polaris or simply the North Star.

The earth is not a perfect sphere, but has an equatorial diameter that is slightly larger than its polar diameter. The sun, moon, and other planets of the solar system exert a gravitational attraction on the equatorial bulge of the earth. It is this force that is responsible for precession.

The positions of the celestial poles actually move across the sky, tracing out a circle with a diameter of about 47° on the celestial sphere every 25,800 years. Therefore, the pole star observed thousands of years ago was not the star we see near the north celestial pole today. For example, in Egypt when the pyramids were being built, the north star was α Draconis, also known as Thuban, the brightest star in the constellation Draco.

Precession does not alter the constellation outlines or change their boundaries with respect to the stars, but causes a slow drift of the entire celestial coordinate system on the celestial sphere.

CyberSky calculates the effect of precession for objects in the display.


Proper Motion (μ)

Yearly apparent angular motion of a star across the celestial sphere. Stars do actually move through space, and the change in their position with respect to the moving the solar system also causes their apparent position to change.

Because stars are so far away, it takes thousands of years for stars to move far enough for this effect to be noticeable to the naked eye.

Proper motion was discovered by Halley around 1715 when he compared the position of the star α Bootis, also known as Arcturus, with its position in ancient star charts.

CyberSky calculates the effect of proper motion for stars in the display.


Proper Name

Name given to one of the brighter stars in the sky. Examples are Vega, Betelgeuse, and Rigel. CyberSky can display proper names for about 250 stars, although only about two or three dozen such names are in common use.


Quadrature

Moment when a planet’s elongation is 90°.

See the Diagrams section of this help file for a diagram illustrating orbital terminology.


Retrograde Motion

Apparent east to west motion of a planet as seen from the earth against the background of stars. Such apparent backward motion occurs when the earth is overtaken by an inferior planet near inferior conjunction or overtakes a superior planet near opposition. The result is that the planet appears to slow down, reverses its direction, slows down again, and then continues its “normal” direct motion.

See the Diagrams section of this help file for a diagram illustrating direct and retrograde motion.


Revolution

Orbital motion of a body around a gravitational center of attraction.


Right Ascension (RA, or α)

Angular distance of a celestial object east or west of the vernal equinox to the hour circle of the object. Right ascension and declination are coordinates in the equatorial coordinate system.

Right ascension is analogous to longitude on the earth’s surface. Right ascension is usually measured in units of hours, minutes, and seconds from 0h to 24h, or less commonly, degrees from 0° to 360°.


Rising Time

Time at which a celestial object appears above the local horizon.

CyberSky’s Star Data, Sun Data, Moon Data, and Planet Data dialog boxes display the time at which an object will rise.

Times are given to the nearest minute. It makes no sense to given them more accurately due to unpredictable disturbances of the atmosphere.


Rotation

Turning of a body on its axis. Almost all celestial bodies show some degree of rotation.


Setting Time

Time at which a celestial object disappears below the local horizon.

CyberSky’s Star Data, Sun Data, Moon Data, and Planet Data dialog boxes display the time at which an object will set.

Times are given to the nearest minute. It makes no sense to given them more accurately due to unpredictable disturbances of the atmosphere.


Sidereal Day

Length of time required for the earth to turn on its axis such that a star viewed by an observer returns to the same position in the sky. A sidereal day is divided into 24 hours, and is equal to about 23h 56m 4s of mean solar time.

See the Diagrams section of this help file for a diagram illustrating the difference between solar and sidereal time.


Sidereal Time

Time measured by reference to the rotation of the earth with respect to the stars. Our common solar time is measured by reference to the rotation of the earth with respect to the sun.

With respect to the stars, the earth takes about 23h 56m 4s to spin once on its axis. This quantity is known as a sidereal day. During this period the earth moves along its orbit around the sun. Because of this motion, it takes roughly another four minutes before the earth has rotated once on its axis with respect to the sun. This 24-hour period is known as a solar day.

The sidereal time at any location is equal to the hour angle of the vernal equinox.

See the Diagrams section of this help file for a diagram illustrating the difference between solar and sidereal time.


Solar Day

Length of time required for the earth to turn on its axis such that the sun returns to the same position in the sky. A solar day is 24 hours long.

See the Diagrams section of this help file for a diagram illustrating the difference between solar and sidereal time.


Solar System

Sun and a large number of objects gravitationally bound to it. These objects include the nine planets Mercury, Venus, the earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto; the moons of the nine planets; and numerous asteroids, comets, and meteoroids.

The solar system is located about 30,000 light-years from the center of the Milky Way galaxy.


Solstice

One of the two points at which the sun reaches its northernmost or southernmost points on the ecliptic. This term is also applied to the moment the sun reaches such a point. See Summer Solstice and Winter Solstice.


Spectral Type

Groups into which stars are assigned according to the characteristics of absorption lines and bands in their spectra. These spectral features are caused by the presence of atoms and molecules in the outer layers of the stars.


Spectrum

Display of the dispersal of radiation from a celestial object into its constituent wavelengths. Such a display allows one to observe the wavelengths present in the radiation and their relative intensities.

One familiar example of a spectrum is a rainbow, in which the visible wavelengths of sunlight are dispersed so that the sequence red, orange, yellow, green, blue, indigo, and violet can be observed.


Star

Spherical, gaseous body that generates energy by nuclear fusion reactions in its core. These reactions convert hydrogen into helium, and helium into heavier elements, and allow a typical star to shine for billions of years.

Some stars appear bluish, others appear yellowish, and others appear reddish. These different colors are due to a difference in temperature. Bluish stars are the hottest and reddish stars are the coolest.

Many of the stars you see in the sky are much like the sun. Some are many times brighter and hundreds of times larger than the sun. If such a star were placed where our sun is, the planets of the inner solar system, including the earth, would be inside the star.

The sun is a typical star, one of about 200 billion stars that make up the Milky Way galaxy.


Summer Solstice

Time when the sun reaches the northernmost point of the ecliptic. This occurs about June 21 and marks the beginning of summer in the northern hemisphere and the day having the maximum hours of sunlight. It also marks the beginning of winter in the southern hemisphere and the day having the maximum hours of darkness.


Sun

Star that is the center of the solar system. The sun is a typical star in the Milky Way galaxy.

The term sun is sometimes used generally as a synonym for star.


Superior Conjunction

Moment at which the elongation of a celestial body on the far side of the sun is 0°.

See the Diagrams section of this help file for a diagram illustrating orbital terminology.


Superior Planet

Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto. These planets lie farther from the sun than the earth.


Synodic Period

Average length of time between successive oppositions, conjunctions, or quadratures of a given planet.


Terminator

Dividing line between the illuminated and dark portions of the lunar or any planetary disk. The line of sunrise or sunset on that body.


Transit

Passage of a small celestial body in front of a much larger one, such as when Mercury or Venus appear in silhouette against the solar disk, or when a satellite passes in front of Jupiter or Saturn, The shadow of a satellite may also transit the disk of its primary.


Transit Time

Time at which a celestial object crosses the observer’s celestial meridian.

CyberSky’s Star Data, Sun Data, Moon Data, and Planet Data dialog boxes display the time at which an object will transit.

Times are given to the nearest minute. It makes no sense to given them more accurately due to unpredictable disturbances of the atmosphere.


Universal Time (UT, GMT)

Universal time is the mean solar time in the time zone centered on Greenwich, England. It is the same thing as Greenwich Mean Time.


Universe

Everything there is. Another term for cosmos.


Variable Star

Star whose brightness varies with time. The period of time between successive peaks in the brightness of such a star can vary from hours to years. Some variable stars have very regular periods, and others have irregular periods. Some variable stars change their brightness so little that this change is only noticed after careful observation over time. Other variable stars change their brightness drastically, easily visible to the naked eye in the night sky, but then disappearing from view, only to brighten and reappear months later. The most common type of variable stars are red giants that appear to pulsate, expanding and contracting like a beating heart.


Vernal Equinox

Time when the sun crosses the celestial equator moving from south to north. This takes places about March 21 and marks the beginning of spring in the northern hemisphere and the beginning of fall in the southern hemisphere.

The sun crosses the celestial equator where the ecliptic and the celestial equator intersect. The point of the vernal equinox is also called the First Point of Aries and is important because it is the zero point for both the equatorial and ecliptic coordinate systems. That is, both right ascension and ecliptic longitude are measured eastward from this point.

The equinoxes are not fixed but move approximately 50 arc seconds per year due to the effect of precession. The vernal equinox or First Point of Ares is now actually located in the constellation Pisces.


Vertical Circle

Circle on the celestial sphere, drawn through the observer’s zenith and perpendicular to the horizon.


Wane

Term used to describe that portion of the lunar revolution between full and new, when the illuminated area of the disk is decreasing. Opposite of wax.


Wax

Term used to describe that portion of the lunar revolution between new and full, when the illuminated area of the disk is increasing. Opposite of wane.


Winter Solstice

Time when the sun reaches the southernmost point of the ecliptic. This occurs about December 21 and marks the beginning of winter in the northern hemisphere and the day having the maximum hours of darkness. It also marks the beginning of summer in the southern hemisphere and the day having the maximum hours of sunlight.


Zenith

Point on the celestial sphere that lies directly above an observer. This point lies directly opposite the observer’s nadir.


Zodiac

Band around 20° wide passing around the celestial sphere centered on the ecliptic. This band is divided into 12 equal sections 30° in length called signs of the zodiac. The names of these sections correspond to the constellations located in them at the time of Hipparchus, over 2000 years ago.

The signs of the zodiac are called Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius, and Pisces. Precession of the equinoxes has shifted the zodiac constellations by over 30° meaning that the signs of the zodiac and the zodiac constellations no longer correspond. For example, spring begins when the sun enters the sign of Aries, but this point is now located in the constellation Pisces. Furthermore, during the course of one year the sun now passes through the constellation Ophiucus, although this constellation is not considered a sign of the zodiac.


Zodiacal Light

Faint glow that extends away from the sun in the ecliptic plane of the sky, visible to the naked eye in the western sky shortly after sunset or in the eastern sky shortly before sunrise. Zodiacal light is best seen on a clear, moonless night in the tropical latitudes. Zodiacal light is sunlight scattered by very small dust particles in interplanetary space concentrated in the plane of the solar system.


Diagram 1—Solar and Sidereal Time

This diagram illustrates the difference between solar and sidereal time. At point A the sun and a distant star lie in the same direction. As the earth moves along its orbit from point A to point B, it rotates exactly once with respect to the star. At point B the star has returned to the same position in the sky it had at point A. Because the earth has moved along its orbit the sun is now located at a different position in the sky. While the earth moves along its orbit from point B to point C it rotates approximately another degree so that the sun is in the same position in the sky it had at point A.

It takes the earth 23 h 56 m 4 s to move from point A to point B, and 24 h to move from point A to point C. These intervals are known as a solar day and a sidereal day, respectively.

See Also

Solar and Sidereal Time


Diagram 2—Orbits

This diagram illustrates the terminology used to describe the positions of planets in relation to the sun and the earth.

The smallest circle represents the orbit of an inferior planet such as Mercury or Venus. The middle circle represents the orbit of the earth. The largest circle represents the orbit of a superior planet such as Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto.


Diagram 3—Retrograde Motion

This diagram illustrates the motion of the earth and a superior planet such as Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto in their respective orbits.

The earth moves faster along its orbit than does the superior planet, which results in an effect called retrograde motion. The superior planet appears to slow down in the sky and reverses its direction near opposition. After opposition the superior planet again slows down and then begins to move in its previous direction.

The inferior planets Mercury and Venus also exhibit retrograde motion, but in their case the cause is that they move faster along their orbits than does the earth.

See Also

Retrograde Motion of an Inferior Planet

Retrograde Motion of a Superior Planet


Greek Alphabet
Table 1—Greek Alphabet

This table contains the lowercase letters of the Greek alphabet that are used in the system of stellar nomenclature devised by Bayer. The brightest star in a given constellation is designated α, the second brightest β, the third brightest γ, and so on.

No	Letter	Name	No	Letter	Name
1	α	Alpha	13	ν	Nu
2	β	Beta	14	ξ	Xi
3	γ	Gamma	15	ο	Omicron
4	δ	Delta	16	π	Pi
5	ε	Epsilon	17	ρ	Rho
6	ζ	Zeta	18	σ	Sigma
7	η	Eta	19	τ	Tau
8	θ	Theta	20	υ	Upsilon
9	ι	Iota	21	φ	Phi
10	κ	Kappa	22	χ	Chi
11	λ	Lambda	23	ψ	Psi
12	μ	Mu	24	ω	Omega


Constellations
Table 2—Constellations

This table contains the three-letter abbreviation, name, genitive form, and English description of all 88 constellations recognized by the International Astronomical Union.

Abbrev	Name	Genitive	English Description
And	Andromeda	Andromedae	Daughter of Cepheus
Ant	Antlia	Antliae	Air Pump
Aps	Apus	Apodis	Bird of Paradise
Aqr	Aquarius	Aquarii	Water Bearer
Aql	Aquila	Aquilae	Eagle
Ara	Ara	Arae	Altar
Ari	Aries	Arietis	Ram
Aur	Auriga	Aurigae	Charioteer
Boo	Bootes	Bootis	Bear Driver
Cae	Caelum	Caeli	Sculptor’s Chisel
Cam	Camelopardalis	Camelopardalis	Giraffe
Cnc	Cancer	Cancri	Crab
CVn	Canes Venatici	Canum Venaticorum	Hunting Dogs
CMa	Canis Major	Canis Majoris	Larger Dog
CMi	Canis Minor	Canis Minoris	Smaller Dog
Cap	Capricornus	Capricorni	Sea Goat
Car	Carina	Carinae	Keel
Cas	Cassiopeia	Cassiopeiae	Mother of Andromeda
Cen	Centaurus	Centauri	Centaur
Cep	Cepheus	Cephei	King of Ethiopia
Cet	Cetus	Ceti	Whale
Cha	Chamaeleon	Chamaeleontis	Chameleon
Cir	Circinus	Circini	Compasses
Col	Columba	Columbae	Dove
Com	Coma Berenices	Comae Berenices	Berenice’s Hair
CrA	Corona Australis	Coronae Australis	Southern Crown
CrB	Corona Borealis	Coronae Borealis	Northern Crown
Crv	Corvus	Corvi	Crow
Crt	Crater	Crateris	Cup
Cru	Crux	Crucis	Southern Cross
Cyg	Cygnus	Cygni	Swan
Del	Delphinus	Delphini	Dolphin
Dor	Dorado	Doradus	Swordfish
Dra	Draco	Draconis	Dragon
Equ	Equuleus	Equulei	Little Horse
Eri	Eridanus	Eridani	River
For	Fornax	Fornacis	Laboratory Furnace
Gem	Gemini	Geminorum	Twins
Gru	Grus	Gruis	Crane
Her	Hercules	Herculis	Hercules
Hor	Horologium	Horologii	Clock
Hya	Hydra	Hydrae	Sea Serpent
Hyi	Hydrus	Hydri	Water Snake
Ind	Indus	Indi	American Indian
Lac	Lacerta	Lacertae	Lizard
Leo	Leo	Leonis	Lion
LMi	Leo Minor	Leonis Minoris	Smaller Lion
Lep	Lepus	Leporis	Hare
Lib	Libra	Librae	Scales
Lup	Lupus	Lupi	Wolf
Lyn	Lynx	Lyncis	Lynx
Lyr	Lyra	Lyrae	Lyre
Men	Mensa	Mensae	Table Mountain
Mic	Microscopium	Microscopii	Microscope
Mon	Monoceros	Monocerotis	Unicorn
Mus	Musca	Muscae	Fly
Nor	Norma	Normae	Carpenter’s Square
Oct	Octans	Octantis	Octant
Oph	Ophiuchus	Ophiuchi	Serpent Holder
Ori	Orion	Orionis	Hunter
Pav	Pavo	Pavonis	Peacock
Peg	Pegasus	Pegasi	Winged Horse
Per	Perseus	Persei	Son of Zeus
Phe	Phoenix	Phoenicis	Phoenix
Pic	Pictor	Pictoris	Painter’s Easel
Psc	Pisces	Piscium	Fish
PsA	Piscis Austrinus	Piscis Austrini	Southern Fish
Pup	Puppis	Puppis	Stern
Pyx	Pyxis	Pyxidis	Mariner’s Compass
Ret	Reticulum	Reticuli	Net
Sge	Sagitta	Sagittae	Arrow
Sgr	Sagittarius	Sagittarii	Archer
Sco	Scorpius	Scorpii	Scorpion
Scl	Sculptor	Sculptoris	Sculptor’s Workshop
Sct	Scutum	Scuti	Shield
Ser	Serpens	Serpentis	Serpent
Sex	Sextans	Sextantis	Sextant
Tau	Taurus	Tauri	Bull
Tel	Telescopium	Telescopii	Telescope
Tri	Triangulum	Trianguli	Triangle
TrA	Triangulum Australe	Trianguli Australis	Southern Triangle
Tuc	Tucana	Tucanae	Toucan
UMa	Ursa Major	Ursae Majoris	Larger Bear
UMi	Ursa Minor	Ursae Minoris	Smaller Bear
Vel	Vela	Velorum	Sail
Vir	Virgo	Virginis	Virgin
Vol	Volans	Volantis	Flying Fish
Vul	Vulpecula	Vulpeculae	Fox


Spectral Types
Table 3—Spectral Types

This table describes the spectral types into which stars are classified. The system in use today was developed by Annie Jump Cannon and her colleagues at Harvard Observatory and was internationally adopted in 1910.

The light of stars can be dispersed into a spectrum and recorded. Features observed in the spectra of stars allow them to be arranged in spectral types. These features include the presence, absence, and relative strengths of absorption and emission lines.

Type	Temp (K)	Color	Spectral Characteristics	Examples
O	30,000	Blue	Ionized helium absorption lines are dominant. Neutral helium lines are weak. Strong ultraviolet continuum.	ζ Puppis 10 Lacertae
B	20,000	Blue	Neutral helium absorption lines are dominant. Virtually no ionized helium lines. Hydrogen lines strengthening.	Rigel Spica
A	9,000	Blue-White	Hydrogen absorption lines are dominant. Some ionized metals, such as iron, silicon, and magnesium, are strong. Ionized calcium is strengthening. Some neutral metal lines.	Sirius Vega
F	6,600	White	Hydrogen lines weakening. Ionized calcium H and K lines strengthening. Neutral metal lines are strengthening.	Canopus Procyon
G	5,500	Yellow	Very weak hydrogen lines. Ionized calcium H and K lines are strong. Neutral metals, such as iron, manganese, and calcium, are strengthening.	Capella Sun
K	4,000	Orange	Calcium H and K lines are strong, as are neutral metal lines. Molecular bands, such as titanium oxide, begin to appear.	Arcturus Aldebaran
M	2,800	Red	Neutral metal lines are strong, as are molecular bands. Titanium oxide is dominant in cooler stars in this class. Vanadium oxide bands begin to appear.	Antares Betelgeuse

These modifiers are appended to the above spectral types to indicate the presence of peculiar spectral features.

Modifier	Spectral Characteristics
e	Emissions lines present
n	Nebulous lines present
s	Sharp lines
k	Interstellar lines present
m	Metallic lines present
p	Peculiar spectrum
v	Variable


Luminosity Classes
Table 4—Luminosity Classes

This table lists the six luminosity classes into which stars are classified. WW Morgan and PC Keenan introduced the currently used M–K luminosity classification scheme in 1937. This scheme defines luminosity classes directly in terms of observational criteria.

Class	Stars
I	Supergiants
II	Bright Giants
III	Giants
IV	Subgiants
V	Dwarfs (Main Sequence)
VI	Subdwarfs

Stars in each group can be further differentiated by the use of the suffixes “a”, “ab”, and “b”.


Physical Data
Table 5—Physical Data

This table contains physical data for the sun, moon, and planets of the solar system.

Name	Mass	Diameter	Density
	Earth = 1	Earth = 1	Water = 1
Sun	332,946	109.12
Moon	0.0123	0.2725	3.3
Mercury	0.055	0.382	5.42
Venus	0.815	0.949	5.25
Earth	1.0	1.0	5.52
Mars	0.1074	0.532	3.94
Jupiter	317.89	11.27	1.314
Saturn	95.17	9.44	0.69
Uranus	14.56	4.1	1.29
Neptune	17.24	3.88	1.64
Pluto	0.11	0.5	2.03
Name	Rotation Period	Ave Temp	Albedo
Sun	25.4 d
Moon	27.322 d
Mercury	58.65 d	200 °C	0.06
Venus	243.0 d (R)	450	0.76
Earth	23.93 h	10	0.36
Mars	1.026 d	-50	0.16
Jupiter	9.8 h	-150	0.73
Saturn	10.2 h	-185	0.76
Uranus	17.9 h	-215	0.93
Neptune	19.1 h	-225	0.84
Pluto	6.39 d	-235	0.14

The symbol (R) behind the rotation period of Venus indicates that Venus’ rotation is retrograde. This is, it rotates in the opposite direction as do the earth and other planets.

For the earth

Mass = 5.976 x 10^27 g

Diameter = 7923 mi = 12,756 km


Orbital Data
Table 6—Orbital Data

This table contains orbital data for the planets of the solar system.

Planet	Orbital Radius	Revolution Period	Synodic Period
Mercury	0.387 AU	87.97 d	115.88 d
Venus	0.723	224.7 d	583.92
Earth	1.000	365.26 d
Mars	1.524	686.98 d	779.94
Jupiter	5.203	11.86 y	398.88
Saturn	9.539	29.46 y	378.09
Uranus	19.182	84 y	369.66
Neptune	30.058	164.8 y	367.49
Pluto	39.53	247.7 y	366.7
Planet	Inclination	Eccentricity	Orbital Velocity
Mercury	7.0°	0.206	47.87 km/s
Venus	3.39	0.007	35.02
Earth	0.0	0.017	29.79
Mars	1.85	0.093	24.13
Jupiter	1.31	0.048	13.06
Saturn	2.49	0.056	9.65
Uranus	0.77	0.047	6.80
Neptune	1.77	0.009	5.43
Pluto	17.15	0.248


Units of Distance
Table 7—Units of Distance

This table contains conversions between units of distance commonly used in astronomy.

Unit	Abbreviation	Equivalent To
1 mile	mi	1.61 kilometers
1 kilometer	km	0.62 mile
1 astronomical unit	AU	93 million miles
		150 million kilometers
1 light-year	ly	5.88 trillion miles
		9.46 trillion kilometers
		63,240 astronomical units
		0.307 parsec
1 parsec	pc	19.2 trillion miles
		30.9 trillion kilometers
		206,265 astronomical units
		3.26 light-years


Upgrades

CyberSky will be periodically updated to add new features, incorporate suggestions received from registered users, fix bugs discovered in the program, and correct errors in its supporting documentation.

Registered users you will receive notification when future versions of CyberSky become available, and will be able to upgrade at a discount from the usual price of a registered copy.


Reporting Bugs

All software contains bugs and CyberSky is no exception. If you encounter a problem with CyberSky please report it to me so that I can try to fix it and make the program better for you and other users.

Bug reports must contain a certain amount of information in order for me to have a chance of finding the cause of the problem and fixing it. If you send me a bug report, please include the following information.

What type of computer are you using?

How much memory does your computer have?

Which version of Windows are you running?

Does the problem you have experienced repeat itself regularly or does it happen sporadically?

If the problem repeats itself regularly, what steps do you perform so that the bug repeats itself?


Contacting the Author

E-mail is the fastest way to contact me. I check my CompuServe mail daily and my UCLA account every business day.

CompuServe	76763,1065

Internet	76763.1065@compuserve.com

stephen@eggneb.astro.ucla.edu

You can also send postal mail to my business address.

Mail	Stephen Michael Schimpf

2444 West 230th Street

Torrance, CA 90501–5242

United States of America

If you feel it is necessary to speak to me, you can call me at the following number between the hours of 10:00 AM and 1:00 PM Pacific time on business days only.

Telephone	310–530–6766


About CyberSky Dialog Box

The About CyberSky dialog box displays the application’s name and version number, release date, legal copyright message, and a large version of the icon. The amount of free memory and free system resources is also displayed.


Color Browser Dialog Box

The Color Browser dialog box allows you to preview and select among 80 colors labeled with spiffy names such as “Tomato” and “Cornflower Blue”.

Click on an item for more information.


Colors

Select a color in this list and then choose the OK button, or simply double-click the color.


OK

Accept the selected color and return to the Colors dialog box.


Cancel

Cancel any changes you made and return to the Colors dialog box.


Help

Display help for the dialog box.


Colors Dialog Box

The Colors dialog box allows you to customize the color of an element of the display.

Click on an item for more information.

When you exit CyberSky the settings in this dialog box are saved. The next time you start CyberSky these values are used as the default values.


Color

Displays the color of the currently selected display element. Choose the Change button or double-click on the element in the list to change its color.


Display Element

Select an element in this list and then choose the Change button, or simply double-click on any element to change its color.


OK

Accept all the color changes you have made and return to the display.


Cancel

Cancel any color changes you have made and return to the display.


Change

Change the color of the element selected in the list.


Reset

Reset the color of the element selected in the list to its original color.


Reset All

Reset the colors of the all elements their original colors.


Help

Display help for the dialog box.


Confirmation Dialog Box

The Confirmation dialog box allows you to specify whether you want CyberSky to perform an action such as replacing old location data with new location data or deleting location data from the location database. Choose the Yes button to perform the action you are asked to confirm. Choose the No button if you do not want that action to be performed.


Date and Time Dialog Box

The Date and Time dialog box allows you to specify the date and time for which you want to see the sky displayed.

Click on an item for more information.

When you exit CyberSky the daylight-saving time setting in this dialog box is saved. The next time you start CyberSky this value is used as the default value.


Date

Specify the local date. Select the month from the list of month names, and then type in the day of the month in the range 1 to 28, 29, 30, or 31. Then type in the year in the range 1 to 4000. Specify whether the year you typed is BC or AD.


Time

Specify the local time in the Time box. Type in the hours, minutes, and seconds.


Daylight-Saving Time

Check the check box in the DST group to indicate to specify that daylight-saving time is in effect. This will cause one hour to be subtracted from the time zone value used to convert from local time to universal time.


OK

Accept the date, time, and daylight-saving time state and return to the display.


Cancel

Cancel any changes you made and return to the display.


Now

Set the date and time values to your computer’s current system date and time.


Midnight

Set the time values to midnight, 00:00:00.


Noon

Set the time values to noon, 12:00:00.


Help

Display help for the dialog box.


Edit Location Dialog Box

The Edit Location dialog box allows you to edit the data associated with a location in the application’s location database.

Click on an item for more information.

When you exit CyberSky the data for the location in this dialog box is saved. These values will define the location until you change them.


Location

Type the name of the location in a format such as Country: City, State. The name can be up to 64 characters long.


Latitude

Type the latitude in decimal degrees in the Latitude box. Select North or South for this latitude. Do not use a minus sign to indicate south latitude.


Longitude

Type the longitude in decimal degrees in the Longitude box. Select East or West for this longitude. Do not use a minus sign to indicate west longitude.


Time Zone

Type the time zone in decimal hours in the Time Zone box. The time zone is the difference between local time and universal time for that time zone. Select Ahead or Behind for this time zone to indicate whether the time zone is ahead or behind universal time. Do not use a minus sign to indicate hours behind universal time.


OK

Accept the definition of the location and return to the Location dialog box.


Cancel

Cancel any changes you made and return to the Location dialog box.


Help

Display help for the dialog box.


Font Dialog Box

The common Font dialog box allows you to choose the screen font or printer font used in the legend. Any changes you make in the Font dialog box are saved between sessions.


Location Dialog Box

The Location dialog box allows you to select a location from the application’s location database.

Click on an item for more information.

When you exit CyberSky the setting in this dialog box is saved. The next time you start CyberSky this value is used as the default value.


Location

Choose a location from any of the locations in this list. Each named location has three properties associated with it: latitude, longitude, and time zone. Each of these values affects the appearance of the display.


OK

Accept the location you selected and return to the display.


Cancel

Cancel the selection you made and return to the display.


Edit

Edit the data for the currently selected location.


Add

Add a new location to the location database.


Delete

Delete the currently selected location from the location database.


Help

Display help for the dialog box.


Moon Data Dialog Box

The Moon Data dialog box appears when you click on the moon with the left mouse button. The dialog box displays information about the moon.

Click on an item for more information.


Disk

View of the lunar disk. This view makes it easier to identify the lunar phase than does the moon symbol in the display.


OK

Return to the display.


Help

Display help for the dialog box.


Orientation Dialog Box

The Orientation dialog box allows you to specify which horizon is positioned at the bottom of the display.

Click on an item for more information.

When you exit CyberSky the setting in this dialog box is saved. The next time you start CyberSky this value is used as the default value.


Horizon

Select a radio button in this group to choose which horizon will be positioned at the bottom of the display.


OK

Accept the orientation you selected and return to the display.


Cancel

Cancel your selection and return to the display.


Help

Display help for the dialog box.


Planet Data Dialog Box

The Planet Data dialog box appears when you click on a planet with the left mouse button. The dialog box displays information about the planet.

Click on an item for more information.


Disk

View of the planetary disk. This view is most useful for Mercury, Venus, and Mars, but is included for the rest of the planets for completeness.


OK

Return to the display.


Help

Display help for the dialog box.


Print Dialog Box

The common Print dialog box allows you to specify printing options and print the display. Specify the printer on which the display should be printed, the print quality, the number of copies you want to print, and any other appropriate options. Choose the OK button to print the display.

Before printing the display you may want to use the Print Preview command on the File menu to preview the printed display.


Print Setup Dialog Box

The common Print Setup dialog box allows you to specify printer options before printing the display. Specify the printer on which the display should be printed, choose either portrait or landscape orientation, select the size of the paper on which the display should be printed, and any other options available to your specific brand and model of printer. Choose the OK button to return to the Print dialog box or the display.


Star Data Dialog Box

The Star Data dialog box appears when you click on a star with the left mouse button. The dialog box displays information about the star.

Click on an item for more information.


OK

Return to the display.


Help

Display help for the dialog box.


Stars Dialog Box

The Stars dialog box allows you to specify options that deal with the stars in the display.

Click on an item for more information.

When you exit CyberSky the settings in this dialog box are saved. The next time you start CyberSky these values are used as the default values.


Limiting Magnitude

Use the scroll bar in this group to choose a limiting magnitude between 3.0 and 6.0. Remember that the more stars that are displayed, the longer it will take to generate the display. For those of you without a math coprocessor, this can make a big difference.

Selecting 6.0 as a limiting magnitude will display all 5028 stars in the CyberSky database. You only see about half this many stars at one time because you only see half of the sky at one time. Also, you will only be able to see down to magnitude 6 under very good seeing conditions far away from city lights. Therefore, under such conditions you will see about 2500 stars in the entire sky, even though you think you are seeing "a million" stars.


Color

Check this check box to display the brightest stars in colors based on their B - V color indices. Clear this check box to display all stars in white.


OK

Accept the changes you made and return to the display.


Cancel

Cancel any changes you made and return to the display.


Help

Display help for the dialog box.


Sun Data Dialog Box

The Sun Data dialog box appears when you click on the sun with the right mouse button. The dialog box displays information about the sun.

Click on an item for more information.


OK

Return to the display.


Help

Display help for the dialog box.


Time Step Dialog Box

The Time Step dialog box allows you to specify the time step between animation frames.

Click on an item for more information.

When you exit CyberSky the setting in this dialog box is saved. The next time you start CyberSky this value is used as the default value.


Time Step

Select a radio button in this group to choose a time step of 1, 2, 5, 10, 15, or 30 minutes; 1 hour; 1 or 7 solar days, or 1 or 7 sidereal days.

If you select the Real Time option, the display will change slowly to reflect the current appearance of the sky. The display will be updated every 30 seconds.


OK

Accept the time step you selected and return to the display.


Cancel

Cancel your selection and return to the display.


Help

Display help for the dialog box.


Toolbar Options Dialog Box

The Toolbar Options dialog box allows you to specify whether ToolTips and FlyBys should be displayed, the style of ToolTip windows, and the delay time.

Click on an item for more information.

When you exit CyberSky the settings in this dialog box are saved. The next time you start CyberSky these value are used as the default values.


View

Check these check boxes to specify that ToolTips and FlyBys should be displayed.

A ToolTip is a short hint to remind you of what a given toolbar button does. If you leave the cursor over a toolbar button for a short time, a small window containing the hint will appear just below the cursor.

A FlyBy is a longer description telling you what a given toolbar button does. The description will appear in the application’s status bar at the same time that the toolbar button’s ToolTip appears. If you have specified that ToolTips should not be displayed, the FlyBy will appear immediately in the status bar, without any delay. If you have specified that FlyBys should not be displayed, you can still view the description in the status bar by holding down the left mouse button while the cursor is over the button.


ToolTip Style

Select a radio button in this group to choose one of two ToolTip styles, square or rounded.


Delay

Select a radio button in this group to choose no delay, or a delay of 1, 2, or 3 seconds.

The delay value is the amount of time that is allowed to pass from the moment you move the mouse cursor over a toolbar button to the moment that the ToolTip for that button appears. If you move the cursor over other toolbar buttons, ToolTips for those buttons will appear immediately.


OK

Accept any changes you made and return to the display.


Cancel

Ignore any changes you made and return to the display.


Help

Display help for the dialog box.


View Dialog Box

The View dialog box allows you to specify exactly what you want included in or excluded from the display.

Click on an item for more information.

When you exit CyberSky the settings in this dialog box are saved. The next time you start CyberSky these value are used as the default values.


Objects

Check the check boxes in this group to include the stars, sun, moon, and planets in the display.


Constellations

Check the check boxes in this group to include the constellations of the zodiac, as well as major and minor constellations in the display. Check all three boxes to include all 88 constellations.


Lines

Check the check boxes in this group to include the ecliptic, celestial equator, galactic equator, and equatorial coordinate system grid lines in the display.


North/South Poles

Check the check boxes in this group to include the North and South poles of the ecliptic, celestial equator, and galactic equator coordinate systems in the display.


OK

Accept the changes you made and return to the display.


Cancel

Cancel any changes you made and return to the display.


Help

Display help for the dialog box.