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Newsgroups: comp.sources.x From: ecdowney@pobox.cca.cr.rockwell.com (Elwood Downey) Subject: v19i092: xephem - astronomical ephemeris program, Part04/21 Message-ID: <1993May10.220824.7730@sparky.imd.sterling.com> X-Md4-Signature: 1e221bba11579ce080a4bad4137014a1 Date: Mon, 10 May 1993 22:08:24 GMT Approved: chris@sparky.imd.sterling.com Submitted-by: ecdowney@pobox.cca.cr.rockwell.com (Elwood Downey) Posting-number: Volume 19, Issue 92 Archive-name: xephem/part04 Environment: X11r4, OSF/Motif Supersedes: xephem: Volume 16, Issue 112-134 #! /bin/sh # This is a shell archive. Remove anything before this line, then feed it # into a shell via "sh file" or similar. To overwrite existing files, # type "sh file -c". # The tool that generated this appeared in the comp.sources.unix newsgroup; # send mail to comp-sources-unix@uunet.uu.net if you want that tool. # Contents: XEphem.ad xephem.hlp # Wrapped by chris@nova on Mon May 10 16:41:42 1993 PATH=/bin:/usr/bin:/usr/ucb ; export PATH echo If this archive is complete, you will see the following message: echo ' "shar: End of archive 4 (of 21)."' if test -f 'XEphem.ad' -a "${1}" != "-c" ; then echo shar: Will not clobber existing file \"'XEphem.ad'\" else echo shar: Extracting \"'XEphem.ad'\" $9517 characters$ sed "s/^X//" >'XEphem.ad' <<'END_OF_FILE' X! initial circumstances setup X! XEphem supports the following resources related to time: X! XEphem.JD: Julian date X! XEphem.UD: UT date X! XEphem.UT: UT time X! XEphem.LD: Local date X! XEphem.LT: Local time X! XEphem.LST: Local sidereal time X! pick any one to set to "Now" or set enough to be complete (such as JD, or X! UD and UT, or LD and LT). X! the date formats and units for Elevation, Temp and Pressue depend on the X! selected preferences. XXEphem.LT: Now XXEphem.TZName: CDT XXEphem.TZone: 5 XXEphem.Long: 91:40:0 XXEphem.Lat: 41:51:0 XXEphem.Elevation: 800 XXEphem.Temp: 60 XXEphem.Pressure: 29.5 XXEphem.StepSize: RTC XXEphem.Epoch: 2000 XXEphem.NSteps: 1 XXEphem.Pause: 0 XXEphem.TwilightDip: 18 XXEphem.viewsFont: fixed X X! default font X! Xephem tables behave best with a mono-spaced or character-cell font, X! ie, -spacing- either m or c. XXEphem*fontList: fixed X X! main menu colors XXEphem*foreground: blue XXEphem*background: snow X X! select one of Algorithms preferences to set to True XXEphem*Algorithms.Accurate.set: False XXEphem*Algorithms.Fast.set: True X X! select one of DateFormats preferences to set to True XXEphem*DateFormat.MDY.set: True XXEphem*DateFormat.YMD.set: False XXEphem*DateFormat.DMY.set: False X X! select one of Units preferences to set to True XXEphem*Units.English.set: True XXEphem*Units.Metric.set: False X X! default plot and listing filenames XXEphem*Plot*Filename.value: ephem.plt XXEphem*List*Filename.value: ephem.lst X X! default help file name XXEphem.HELPFILE: xephem.hlp X X! default database file name XXEphem*DBPromptD.textString: ephem.db X X! set Geocentric.set to true for geocentric separations, X! or Topocentric.set to true for topocentric separation.. XXEphem*Geocentric.set: false XXEphem*Topocentric.set: true X X! set StdRefr.set to true to use constant 34 arcminute refraction, or X! set AdpRefr.set to true to use current mainmenu atmospheric conditions. XXEphem*AdpRefr.set: false XXEphem*StdRefr.set: true X X! set Limb.set to true to compute rise/set based on upper limb, or X! set Center.set to true to compute rise/set based on object's center. XXEphem*DataSelRisetCols*Center.set: false XXEphem*DataSelRisetCols*Limb.set: true X X! initial location (unless using interactive window manager placement) XXEphem*xephem_main.x: 50 XXEphem*xephem_main.y: 50 X X! infor for the Jupiter display XXEphem*Jupiter*Map*background: #00004a XXEphem*Jupiter*Map*foreground: snow XXEphem*Jupiter*CtlForm.verticalSpacing: 5 XXEphem*Jupiter*BigDots.set: True XXEphem*Jupiter*Tags.set: True XXEphem*Jupiter*Map.height: 100 XXEphem*Jupiter.x: 100 XXEphem*Jupiter.y: 200 X X!info for the Saturn display XXEphem*Saturn*CtlForm.verticalSpacing: 5 XXEphem*Saturn*BigDots.set: True XXEphem*Saturn*Tags.set: True XXEphem*Saturn*Map.height: 100 XXEphem*Saturn.x: 400 XXEphem*Saturn.y: 200 XXEphem*Saturn*Map*background: #00004a XXEphem*Saturn*Map*foreground: snow X X!info for the Moon display XXEphem*Moon*Earthshine.set: True XXEphem*Moon*BitmapView.set: False XXEphem*Moon.x: 200 XXEphem*Moon.y: 200 XXEphem*MoonDA*foreground: snow XXEphem*MoonDA*background: #00004a X X! info for the Mars map XXEphem*Mars.x: 300 XXEphem*Mars.y: 300 XXEphem*Mars*Map.height: 300 XXEphem*Mars*Map.foreground: dark orange XXEphem*Mars*Map.background: gray14 X X! info for the Earth map XXEphem*Earth.x: 200 XXEphem*Earth.y: 200 XXEphem*Earth*Map.height: 300 XXEphem*Earth*Map.foreground: cyan3 XXEphem*Earth*Map.background: gray14 X X! info for the Solar system display XXEphem*SolarSystem.x: 250 XXEphem*SolarSystem.y: 350 XXEphem*SolarSystem.CtlForm.verticalSpacing: 5 XXEphem*SolarSystem.BigDots.set: True XXEphem*SolarSystem.ConnectDots.set: True XXEphem*SolarSystem.Trails.set: False XXEphem*SolarSystem.Names.set: True XXEphem*SolarSystem.HLongScale.value: 0 XXEphem*SolarSystem.DistScale.value: 50 XXEphem*SolarSystem.HLatScale.value: 90 XXEphem*SolarSystem*SolarDA.height: 300 XXEphem*SolarSystem*SolarDA.width: 300 XXEphem*SolarSystem*SolarDA.background: #00004a XXEphem*SolarSystem*SolarDA.foreground: snow XXEphem*StereoSolarSystem*StereoDA.background: #00004a XXEphem*StereoSolarSystem*StereoDA.foreground: snow X X! info for the Sky View display. X! select default Sky View coordinate display mode: X! set one of RADecMode.set or AltAzMode.set to true. X! then set AzRAScale.value and AltDecScale.value to desired initial settings. X! N.B. when using AltAz mode: X! need to set AzRAScale.maximum to 360 since default scale max is 100. X! AzRAScale.decimalPoints is set to 1. X! XEphem*SkyView*RADecMode.set: true XXEphem*SkyView*AltAzMode.set: true XXEphem*SkyView*FOVScale.value: 180 XXEphem*SkyView*AltDecScale.value: 90 XXEphem*SkyView*AzRAScale.value: 180 XXEphem*SkyView*AzRAScale.maximum: 360 XXEphem*SkyView*JustDots.set: True XXEphem*SkyView*Ecliptic.set: False XXEphem*SkyView*AllLabels.set: False XXEphem*SkyView.x: 200 XXEphem*SkyView.y: 400 XXEphem*SkyView*Map.width: 300 XXEphem*SkyView*Map.height: 300 XXEphem*SkyView*Map.background: #00004a XXEphem*SkyView*Map.foreground: snow X X! initial setting of the skyview faint and bright magnitude limits X! BMAGLIMIT and FMAGLIMIT in skyviewmenu.c limit the extremes to -28 and 20. XXEphem*SkyView*FaintMagScale.value: 6 XXEphem*SkyView*BrightMagScale.value: -28 X X! colors used to display the symbols in the Sky View filter menu XXEphem*SkyFilter*SymbolDA.foreground: snow XXEphem*SkyFilter*SymbolDA.background: #00004a X X! initial types of object to display in Sky View XXEphem*SkyFilter*Planets.set: True XXEphem*SkyFilter*Elliptical.set: True XXEphem*SkyFilter*Hyperbolic.set: True XXEphem*SkyFilter*Parabolic.set: True XXEphem*SkyFilter*Quasars.set: True XXEphem*SkyFilter*Stellar.set: True XXEphem*SkyFilter*Undefined.set: True XXEphem*SkyFilter*Stars.set: True XXEphem*SkyFilter*Binary.set: True XXEphem*SkyFilter*Double.set: True XXEphem*SkyFilter*Multiple.set: True XXEphem*SkyFilter*Variable.set: True XXEphem*SkyFilter*BrightNeb.set: True XXEphem*SkyFilter*DiffuseNeb.set: True XXEphem*SkyFilter*DarkNeb.set: True XXEphem*SkyFilter*PlanetaryNeb.set: True XXEphem*SkyFilter*SpiralGal.set: True XXEphem*SkyFilter*SphericalGal.set: True XXEphem*SkyFilter*GalClusters.set: True XXEphem*SkyFilter*GlobularCl.set: True XXEphem*SkyFilter*OpenCl.set: True XXEphem*SkyFilter*ClInNeb.set: True X X! misc display locations and colors XXEphem*Data.x: 100 XXEphem*Data.y: 200 XXEphem*Plot.x: 100 XXEphem*Plot.y: 200 XXEphem*List.x: 500 XXEphem*List.y: 200 XXEphem*Srch.x: 200 XXEphem*Srch.y: 300 XXEphem*AltAzMap*background: #00004a XXEphem*AltAzMap*foreground: snow XXEphem*PlotDA*foreground: #fce089 XXEphem*PlotDA*background: #00004a XXEphem*PlotDA*height: 300 XXEphem*VersionMap*foreground: snow XXEphem*VersionMap*background: #00004a X X! set which Data Table rows and columns are to be on initially XXEphem*DataSelRows.Sun.set: true XXEphem*DataSelRows.Moon.set: true XXEphem*DataSelRows.Mercury.set: false XXEphem*DataSelRows.Venus.set: false XXEphem*DataSelRows.Mars.set: false XXEphem*DataSelRows.Jupiter.set: false XXEphem*DataSelRows.Saturn.set: false XXEphem*DataSelRows.Uranus.set: false XXEphem*DataSelRows.Neptune.set: false XXEphem*DataSelRows.Pluto.set: false XXEphem*DataSelMiscCols.Cns.set: true XXEphem*DataSelMiscCols.R_A.set: true XXEphem*DataSelMiscCols.Dec.set: true XXEphem*DataSelMiscCols.Az.set: true XXEphem*DataSelMiscCols.Alt.set: true XXEphem*DataSelMiscCols.HeLong.set: false XXEphem*DataSelMiscCols.HeLat.set: false XXEphem*DataSelMiscCols.EaDst.set: false XXEphem*DataSelMiscCols.SnDst.set: false XXEphem*DataSelMiscCols.Elong.set: false XXEphem*DataSelMiscCols.Size.set: false XXEphem*DataSelMiscCols.VMag.set: false XXEphem*DataSelMiscCols.Phase.set: false XXEphem*DataSelRisetCols.RiseTm.set: true XXEphem*DataSelRisetCols.RiseAz.set: false XXEphem*DataSelRisetCols.TrnTm.set: false XXEphem*DataSelRisetCols.TrnAlt.set: false XXEphem*DataSelRisetCols.SetTm.set: true XXEphem*DataSelRisetCols.SetAz.set: false XXEphem*DataSelRisetCols.HrsUp.set: false XXEphem*DataSelSepCols.Sun.set: false XXEphem*DataSelSepCols.Moon.set: false XXEphem*DataSelSepCols.Mercury.set: false XXEphem*DataSelSepCols.Venus.set: false XXEphem*DataSelSepCols.Mars.set: false XXEphem*DataSelSepCols.Jupiter.set: false XXEphem*DataSelSepCols.Saturn.set: false XXEphem*DataSelSepCols.Uranus.set: false XXEphem*DataSelSepCols.Neptune.set: false XXEphem*DataSelSepCols.Pluto.set: false X X! colors used to plot the planets and stars XXEphem.mercuryColor: Red XXEphem.venusColor: Green XXEphem.marsColor: OrangeRed XXEphem.jupiterColor: Cyan XXEphem.saturnColor: PaleGoldenrod XXEphem.uranusColor: MediumSpringGreen XXEphem.neptuneColor: DeepSkyBlue1 XXEphem.plutoColor: Orange XXEphem.sunColor: Yellow XXEphem.moonColor: Grey XXEphem.hotStarColor: LightSkyBlue1 XXEphem.mediumStarColor: LemonChiffon XXEphem.coolStarColor: Coral X X! colors used in plots XXEphem.plotColor0: red XXEphem.plotColor1: green XXEphem.plotColor2: blue XXEphem.plotColor3: orange XXEphem.plotColor4: magenta XXEphem.plotColor5: cyan XXEphem.plotColor6: black XXEphem.plotColor7: wheat XXEphem.plotColor8: gray XXEphem.plotColor9: pink X X X! "systemy" sort of defaults not generally changed. XXEphem.allowShellResize: True XXEphem*spacing: 1 XXEphem*marginHeight: 1 XXEphem*traversalOn: false XXEphem*highlightOnEnter: false XXEphem*highlightThickness: 0 XXEphem*XmText*traversalOn: true XXEphem*XmText*highlightOnEnter: false XXEphem*XmText*highlightThickness: 0 X X! Help text scrolled text area dimensions XXEphem*Help*ScrolledText.rows: 24 XXEphem*Help*ScrolledText.columns: 80 XXEphem*Help.verticalSpacing: 20 X X! scrolled Message text scrolled text area dimensions XXEphem*Message*ScrolledText.rows: 10 XXEphem*Message*ScrolledText.columns: 80 XXEphem*Message.verticalSpacing: 20 END_OF_FILE if test 9517 -ne `wc -c <'XEphem.ad'`; then echo shar: \"'XEphem.ad'\" unpacked with wrong size! fi # end of 'XEphem.ad' fi if test -f 'xephem.hlp' -a "${1}" != "-c" ; then echo shar: Will not clobber existing file \"'xephem.hlp'\" else echo shar: Extracting \"'xephem.hlp'\" $65231 characters$ sed "s/^X//" >'xephem.hlp' <<'END_OF_FILE' X@Intro XXephem is a program that computes ephemerides for all the planets, some of Xtheir moons, plus any two user-defined objects. X XIn addition to information in numeric form, xephem displays simple schematic Xviews of Saturn, Jupiter, Mars, Luna and Earth as well as maps of the night Xsky and the solar system. The sky and solar system maps support labeling and Xtrailing, and the solar system can be shown as a stereo pair. X XXephem can compute information on demand or time can be set to increment Xautomatically. In this way a series of computations and movies can be Xgenerated unattended. X XQuantitative information available about each object includes RA and Dec Xprecessed to any epoch, local azimuth and altitude, heliocentric Xcoordinates, distance from sun and earth, solar elongation, angular size, Xvisual magnitude, illumination percentage, local rise, transit and set Xtimes, length of time up, constellation, and angular separations between all Xcombinations of objects. X XObserving circumstance information includes UTC and local date and time, Xlocal sidereal time, times of astronomical twilight and length of night, Xlocal temperature, pressure and elevation above sea level for the refraction Xmodel and a monthly calendar. X XRA/Dec calculations are geocentric and may include the effects of light Xtravel time, nutation, aberration and precession. Alt/Az and Xrise/set/transit and, optionally, angular separation calculations are Xtopocentric and include the additional effects of parallax and refraction. X XPlot and listing files of selected field values may be generated as the Xprogram runs. The plot files are full precision floating point values in XASCII intended for export to other plotting programs. Xephem includes simple Xquick-look facilities to view plot files. The listing files are tables Xformatted for more general human reading. X XXephem can read databases of objects. The objects may be fixed or specified Xvia heliocentric elliptical, hyperbolic or parabolic orbital elements to Xaccommodate solar system objects such as asteroids or comets. These are Xthen available as candidate values for the user defined objects and all of Xthem can be displayed in the sky map subject to type and magnitude filters. XThe format of the database file is described in the Help for the DB menu. X X@MainMenu XAcross the top of the Main menu is a menu bar to allow selecting the Xprinciple display menus of xephem. These may be turned on in any desired Xcombination. Each menu will have its own Close button or it may be closed Xby reselecting it from the main menu bar. X X The "File" pulldown is a few miscellaneous controls. The "Reset" entry will X return xephem to its initial state. The "Messages" entry toggles whether X the general messages menu is displayed. Note that all messages that go X to this menu also appear on stdout regardless of whether the menu is X up. In order to be sure it is seen, the "messages" menu is always moved X to the top of the window stack and placed under the pointer whenever it X is up and new messages are added to it. The "Quit" entry exits xephem. X X The "View" pulldown toggles any of the several xephem displays. X X The "Control" pulldown toggles the plotting, listing and searching control X menus. X X The "ObjX/Y..." pushbutton toggles the menu that allows you to define X the user defined objects, ObjX and ObjY. Said menu also allows you to X inspect each item currently in the xephem database. X X The "DB..." pushbutton toggles the menu that allows to add or replace X entries in the xephem database from files of database objects. X X The "Preferences" pulldown lists the available preferences that may be X changed at runtime. The options currently available include whether the X algorithms are chosen for accuracy or speed; dates are shown and entered X in month/day/year, year/month/day or day/month/year format; and whether X local topocentric circumstances are given in English or Metric units of X measure. Each of these may be initialized via the XEphem resources; see X the sample XEphem.ad resource file for details. When the Algorithm X setting is for Fast, a simpler precession algorithm is used and there X is no correction for light travel time or nutation. Whenever the X preferences are changed at run time, all effected fields are immediately X recalculated. X X Finally, the "Help" pulldown provides access to several general areas of X information. X XThe next row is a status line that contains a short description of what Xxephem is doing at the moment with regards to its looping behavior. X XBelow that is room for the NEW CIRCUMSTANCES message. When you change a Xfield that would invalidate any of the other fields the message NEW XCIRCUMSTANCES appears near the top of the menu. This will remain until at Xleast one screen update loop occurs. X XSee the Help for "Operation" for more information on changing the fields in Xthe Main menu and controlling xephem's runtime behavior. See the Help for X"Triad formats" for more information on these formats. X XFollows is a description of each of the display fields in the Main menu. X X UTC Date The UTC date. X UTC Time The UTC time. X Julian The current Julian date, to about 1-second accuracy. X Sidereal The sidereal time for the current time and location.. X TZ Name The local timezone name. The name field may be changed to any X three-character mnemonic. X TZ Offset Hours local time is behind UTC, ie, positive west or negative X east of Greenwich. X Local Date The local date. This is UTC minus the value of TZ Offset. X Local Time The local time. This is UTC minus the value of TZ Offset. X X Twilight Dip The number of degrees the sun is below the horizon we wish to X call twilight. This sets the value for the following fields. X Dawn Local time when the sun center is "Twilight dip" degrees below X the horizon before sunrise today. X Dusk Local time when the sun center is "Twilight dip" degrees below X the horizon after sunset today. X Night Length Length of astronomical night, ie, Dawn - Dusk. If this and the X display for Dawn and Dusk are shown as "-----", it means the sun X is either always below or always above "Twilight dip" degrees X below the horizon on this particular day. X X N Steps The number of times the display will be updated (time advanced X by Step Size each step) automatically. X Step Size The amount of time UTC (and its derivatives) is incremented X each loop. X Pause Number of seconds to pause between screen updates. This is X used mainly to set up for free-running unattended operation. X Pausing is not done when plotting or searching is on. X X Latitude Location latitude, positive degrees north of equator. X Longitude Location longitude, positive degrees west of Greenwich meridian. X Elevation Local elevation of the ground above sea level, in feet. (see X implementation notes). Used in refraction correction. X Temperature Local surface air temperature, in degrees F. Used in refraction X correction. X Atm Pressure Local surface air pressure, in inches of mercury. Used in X refraction correction. X Epoch The epoch, to the nearest 0.1 years, to which the ra/dec X fields are precessed. This says (OfDate) when coordinates X are not precessed, ie, are in the epoch of date. X XThe calendar on the right of the Main menu is based on UTC. Selecting a date Xbutton will set the date. Unlabeled buttons before the first of the month Xand after the last of the month work as expected to also imply a change in Xmonth or year as necessary. The month and year buttons pop up selections Xthat allow these to be changed as well. In no case does using the calendar Xchange the current time (just the date). X X@Operation XWhen xephem starts it sets the initial values of several fields from several XX resource values. See the Help for "Initialization" for details of the Xformat of these resources. Xephem then draws all fields on the Main screen Xwith their initial values. The program then loops advancing time each step, Xby some amount you may control, and updating all fields each loop. X XThere are three fields that control this looping behavior. "N Steps" Xcontrols the number of steps, "Step Size" the amount of time to add each Xstep, and "Pause" is the amount of real seconds to pause between steps. When Xlooping is in effect, the bottom button on the Main menu says "Stop". (Note Xthat Xephem does not pause between steps when plotting or searching is on.) XWhen the number of steps goes to 0 or the "Stop" button is selected, the Xlooping stops and the button is relabeled "Update". X XNote that when looping with Pause set to 0, most numeric field data are not Xdrawn in order to speed up the display. These values are always updated Xinternally, however. and may safely be used for plotting, searching or Xlisting. This is true even if the menu that displays the information is Xclosed. X XMost fields may be changed by selecting them. A prompt dialog with a brief Xexplanation of the field will be presented. A new value may be typed into Xthe text field provided. If "Ok" is selected the new value will be used; if X"Cancel" is selected the field will be left unchanged. In either case, the Xprompt dialog goes away. Some of the dialogs have an extra button as a handy Xway to enter frequently used values for the field. X XWhen you have changed a field that would invalidate any of the other fields Xthe message NEW CIRCUMSTANCES appears near the top of the Main menu. This Xwill remain until at least one screen update loop occurs. If you change any Xfield that causes new circumstances, the "Step Size" value is not added to Xthe current time after the first loop. Note also that after a series of Xloops, "N Steps" is automatically reset to 1 from 0 so "Update" will do Xexactly one loop again. X@Credits XFirst and foremost, I want to thank my lovely and loving wife, Kathy, for Xfreely accepting me as I am and for encouraging and supporting my passion for Xastronomy in general and writing xephem in particular. X XMany formulas and tables are based, with permission, on material found in: X"Astronomy with your Personal Computer" by Dr. Peter Duffett-Smith, XCambridge University Press, (c) 1985. X XConstellation algorithm is from a paper by Nancy G. Roman, "Identification Xof a constellation from a position", Publications of the Astronomical XSociety of the Pacific, Vol. 99, p. 695-699, July 1987. X XThe high-precision precession routine is from 1989 Astronomical Almanac, as Xinterpreted by Craig Counterman. Mr. Counterman also deserves the credit for Xproviding the initial encouragement to write an astronomical tool Xspecifically for X Windows. X XThe Earth map is derived from one of the demos that comes with gnuplot, XCopyright (C) 1986, 1987, 1990, 1991 Thomas Williams, Colin Kelley. X XThe moon bitmap is derived from xphoon, Copyright (C) 1988 by Jef Poskanzer Xand Craig Leres. X XJupiter's moons based on information in "Astronomical Formulae for XCalculators" by Jean Meeus. Richmond, Va., U.S.A., Willmann-Bell, (c) 1982. X XSaturn's moons based on code supplied by Doug McDonald. X XMany test cases were gleaned from the pages of Sky and Telescope, (C) Sky XPublishing Corp. X XI thank all the organizations behind the incredible Internet for its Xmaintenance and free and easy access. X XNational Space Science Data Center and the Institute for Theoretical XAstronomy of the Russian Academy of Sciences for the asteroid database and Xthe NSSDC and the Smithsonian Astrophysical Observatory for the SAO Xdatabase. X XThe members of the Saguaro Astronomy Club for the preparation and free Xdistribution of their deep-sky database. X XBright stars are from the Yale Bright Star catalog, as edited by Robert Tidd X(inp@violet.berkeley.edu) and Alan Paeth (awpaeth@watcgl.waterloo.edu). Any Xerrors in conversion to the ephem.db format are strictly mine. X XSpecial thanks to all the folks over the years who have provided innumerable Xideas, suggestions and bug reports, both for xephem and its ancestor, Xephem. A major benefit to writing and distributing these programs has been Xthe chance to make friends from around the world. X X@Initialization XMost of the fields in the Main xephem menu can be initialized from the X Xresources for class "XEphem". Of course, you may still change any field Xwhile the program is running too; these just set the initial conditions. X XBecause of the way unspecified triad components are left unchanged (see Xhelp on Triad Formats) always specify all three for all such entries. For Xexample, to initialize the longitude to zero degrees, say 0:0:0, not just 0. X X UD initial UTC date, such as 10/20/1988, or "Now" to use the computer X clock. X UT initial UTC time, such as 12:0:0, or "Now" to use the computer clock. X JD time specified as a Julian Date. X TZone hours the local time is behind utc, such as 5:0:0. You need not X set this if you use "Now" for UT or UD. X TZName name of the local time zone, such as CDT. 3 chars max. You need X not set this if you use "Now" for UT or UD. This is purely a text X label; xephem makes no attempt to compute anything from this label, X such as a UTC offset. X Long longitude, in degrees west of Greenwich, in the form d:m:s. X Lat latitude, in degrees north of the equator, in the form d:m:s. X Elevation height above sea level, in feet or meters, such as 800. Used to X compute parallax of solar system objects. X Temp air temperature, in degrees F or C, such as 60. X Pressure air pressure, in inches of Mercury or mBar, such as 29.50. X Temp and Pressure are used to compute refraction when the AdpHzrn X option is active; see the Help for the Data setup table. X StepSize the time increment between screen updates, such as "1" to give X one hour updates. this can be a specific amount or RTC to use X the system clock as a real-time source. You may also specify a X time in days by appending a D (or d) after the number or a time X in sidereal days by appending an s (or S) after the number. X NSteps number of times program will loop automatically. X see the discussion under Program Operation. X Epoch this sets the desired ra/dec precession epoch. you can put any X date here (use decimal form, such as 1992.5) or "EOD" to use the X current instant ("Epoch of Date"). X Pause The number of seconds to pause between calculation steps. X TwilightDip Number of degrees the sun is below the horizon that you want to X define as being the end of "twilight"; must be at least 0. X@Date/time XXephem uses many values that get are entered in some variation of X/Y/Z form. XWe call this a "triad" input format. X XTimes are displayed and entered in h:m:s format. If you pick a time field Xto change it. Any of the h, m, and s components that are not specified are Xleft unchanged from their current value. For example, 0:5:0 set hours to 0, Xminutes to 5, seconds to 0, whereas :5 sets minutes to 5 but leaves hours Xand seconds unchanged. A negative time is indicated by a minus sign (-) Xanywhere before the first digit. X XDates are displayed and entered in any one of month/day/year, year/month/day Xor day/month/year form. A preference selection on the main menu, and controlled Xby the XEphem resource DateFormat, selects which form is currently being used. X XAs with time, components omitted when entering a new value retain the current Xvalue. For example, if the current date is 10/20/1988 and you type 20/30 Xthe new date will become 20/30/1988. If you then type //2000 the new date will Xbecome 20/30/2000. Note you must type the full year since the program is Xaccurate over several centuries either side of 1900. X XIf you change the date, the time (ie, partial day) will not change. X XNegative years indicate BC dates. For example, Jan 1, 1 BC is given as X1/1/-1. There is no year 0. X XTwo other ways to set the date are supported for compatibility with some Xpublished comet ephemerides. You may enter the day portion as a floating Xpoint number. When you set the day this way, the time will also change to Xcorrespond to the fractional portion of the day. X XYou may also enter a date as a decimal year, as in 1990.12345. Also, when Xthe date format preference is set to M/D/Y or D/M/Y the decimal point may be Xomitted if the value is not a reasonable month or date value, respectively. XDecimal years are useful in interpreting plot files that include a date field, Xsince date fields are stored in plot files as decimal years. Any input that Xincludes exactly one decimal point is assumed to be a decimal year. X XOther parameters such as longitude, latitude and "Step Size" also fall into Xthe general triad format. The same rules apply to these with respect to Xonly having to set the portions that are being changed. X XAs a matter of typing convenience, the program accepts most any punctuation Xcharacter as the separator in a triad; you don't have to type a perfect ":" or X"/". X@Notes X1) The program uses a horizontal plane tangent to the earth Elev feet above Xsea level as the horizon for all altitude calculations, rise/set events, etc. XDue to Earth's curvature, this is not the same as the angle up from the local Xhorizon unless the observer is directly on the ground. The effect can be found Xfrom: X X sin(a)**2 = (h**2 + 2Rh) / (R+h)**2 X where: X R = radius of earth X h = height above ground (same units as R) X a = increase in altitude X XThe effect can be significant. For example, the effect is more than two arc Xminutes at a height of 5 feet. X X2) The accuracy of xephem can not be specifically stated since the Duffett- XSmith book does not warrant its planet position polynomials to any given Xdegree. I know for sure that better accuracy could be achieved if xephem Xused TDT but I have not yet decided on a suitable algorithm. Allowing for Xthis manually, comparisons with the Astronomical Almanac are often within a Xvery few arcseconds. X X3) The sun-moon distance is the solution for the third side of a planar Xtriangle whose two other sides are the earth-moon distance and earth-sun Xdistance separated by the angle of elongation. X X4) The calendar shows UTC, including dates of new and full moon. X X5) The visual magnitudes for the planets take into account the phase of the Xillumination; the magnitudes for other solar system objects do not. X X6) Ideas: X + add tick marks (third axis?) to plots. X + write a tool to find g/k from a set of predicted magnitudes. X + search for occultations with all fixed objects. X + add explicit searching for solar and lunar eclipses. X + do more moons. X + add a shorthand for synodic step sizes. X + add e/w flip option to all displays. X + use FileSelectionBox to choose plot, listing, and database files. X + think of a way to display decimal years in plots as m/d/y. X + incorporate Terrestrial Dynamical Time (known as Ephemeris Time prior to X 1984). TDT is about 57 seconds ahead of UT1 in 1990. X + account for lunar augmentation. X + add undo for plot and listing selections. X + use a progress meter during long operations, not just the watch cursor. X + let xephem put things in the root window. X + add lots more stuff to the Earth display, including interactive selection X and tracking of lat/long and allow different viewpoints. X + compute and display libration info in moon view. X XBugs: X - %0*.* in f_sexad() doesn't work on some systems (needs 0 deleted) X - should jup moon +y be S??? X - the built-in elements for pluto need to be updated. the elements for pluto X in the included ephem.db database sampler are more accurate. X - allow for decimal seconds in format converters. X@Plot XThis menu controls the plot generation and display functionality of xephem. XYou may select most numeric information displayed by xephem, in pairs, to Xform x/y coordinates of a plot. You may select up to ten such pairs. You Xthen select a file to contain the plot information. Xephem adds one line of Xinformation to the file for each x/y pair each time iteration step. Xephem Xcan also plot any such file on the screen. The file format is compatible Xwith the character version of xephem, ephem. X XSelecting data to plot: X XSelect the "Select fields" toggle button to make each field in the other Xmenus that are eligible for plotting appear as a pushbutton. Select each Xsuch button as desired to form the x or y component of a plot. As you make Xthe selections, they are listed in the menu. You may also associate a Xone-character tag with each line. These tags will be included in the plot Xdisplay for identification later. Once all the field choices have been made Xyou may return all the menus to their normal operational appearance by Xreselecting the same toggle button. X XSpecifying the plot file name: X XType the name of the file to be used to contain the plot information in the Xtext field provided. When xephem first needs to write to the file, it will Xfirst check for the existence of the file and, if it already exists, ask Xwhether you wish to append to the file or overwrite it. X XThe default plot file name may be specified as the value of the resource Xnamed "XEphem*Plot*Filename.value". If this resource is not specified then Xthe file name will be "ephem.plt". X XSpecifying a plot file title: X XEnter a short title for the plot information in the text are provided. When Xxephem first writes to a plot file, it will place the contents of the title Xtext area, if it is not empty, into the file as a comment. All lines within Xa plot file that do not begin with an alphanumeric character are considered Xcomments and are ignored. If the first line of a file is a comment, xephem Xwill use it as the title for the plot when it displays the plot. X XGenerating the plot entires: X XOnce the fields have been specified and the plot file named and titled, you Xmay select the "Plot to file" toggle button when ready. Now each time xephem Xgoes through one iteration the values you have selected and their tags will Xbe written to the plot file. Note that when plotting is activated, xephem Xdoes not update the screen until the "N Steps" count goes to 1. This greatly Xspeeds the creation of plot files by avoiding screen updates. If you wish to Xwatch each iteration, set "N Steps" to 1 and select the "Update" button Xmanually for each iteration. Once all the desired data has been entered into Xthe plot file, toggle the plot button back off to flush all data and close Xthe file. X XThe menus that contain each of the fields used in the plot need not be Xvisible while the plot is being generated. X XViewing plot files: X XExisting plot files may be viewed by entering their name into the text field Xprovided and selecting the "Show plot file" pushbutton. As many different Xplot files may be viewed simultaneously as desired. Each plot has separate Xcontrols for flipping the X and Y axes and for turning on and off a Xreference coordinate grid. X XThe xephem distribution kit includes a sample plot file of the analemma. X@Listing XThis menu controls the list generation functionality of xephem. The fields Xyou select define columns of a table written to a file as xephem runs. XThese columns look exactly like their corresponding fields on the xephem Xmenus and so are more familiar and readable than the entries in plot files. XThey are designed to be used in further text processing operations or Xprinted as-is. Two spaces are placed between each column. X XSelecting data to list: X XSelect the "Select fields" toggle button to make each field in the other Xmenus that are eligible for listing appear as a pushbutton. Select each such Xbutton as desired to form each column of the listing. As you make the Xselections, they are listed in the menu. Once all the column choices have Xbeen made you may return all the menus to their normal operational Xappearance by reselecting the same toggle button. X XSpecifying the listing file: X XType the name of the file to be used to contain the listing in the text Xfield provided. When xephem first needs to write to the file, it will first Xcheck for the existence of the file and, if it exists, ask whether you wish Xto append to the file or overwrite it. X XThe default listing file name may be specified as the value of the resource Xnamed "XEphem*List*Filename.value". If this resource is not specified then Xthe file name will be "ephem.lst". X XSpecifying a listing file title: X XAll lines within a listing file that do not begin with an alphanumeric Xcharacter are considered comments and are ignored. When xephem first writes Xto a listing file, it will place the contents of the title text area, if it Xis not empty, into the file as a comment for your convenience. X XGenerating the listing entires: X XOnce the fields have been specified and the listing file named and titled, Xif desired, select the "List to file" toggle button. Now each time xephem Xgoes through one iteration the values you have selected will be written to Xthe file. Note that when listing is activated, xephem does not update the Xscreen until the "N Steps" count goes to 1. This greatly speeds the creation Xof listing files by avoiding screen updates. If you wish to watch each Xiteration, set "N Steps" to 1 and select the "Update" button manually for Xeach iteration. Once all the desired data have been entered into the listing Xfile, toggle the list button back off to flush all data and close the file. X XMenus that contain each of the fields used in the listing need not be Xvisible for the fields to be listable. X@Search XThis menu controls the automatic searching facility. You define an arithmetic Xor boolean function, using most of the fields xephem displays, then xephem Xwill automatically evaluate the function and adjust the time on each Xiteration to search for the goal. X XTo perform a search: X enter a function, X compile it, X select a goal, X set the desired accuracy, X enable searching, X start the search process. X XEach of these steps is described below. X XEntering the function: X XThe function may be any arithmetic expression, in C-language syntax. All of XC's comparison, logical and arithmetic operators are supported as well as Xseveral common arithmetic functions. Here is the complete list: X X + - * / && || > >= == != < <= X abs sin cos tan asin acos atan degrad raddeg pi log log10 exp sqrt pow atan2 X XThe function is entered into the text line provided. It may utilize most of Xthe fields from the other xephem menus. Press the "Enable field buttons" Xbutton to make each available field a button. Where ever a field is desired Xin the function, position the text insertion cursor at the desired position Xand select the field; its name will be inserted into the function text. When Xyou are finished defining the function, turn off the field button appearance Xby selecting the "Enable..." button again. Once you get to know the names Xof the fields you may also enter them manually, if you prefer. X XCompiling the function: X XOnce the function has been entered as desired, it must be compiled by Xselecting the "Compile" button (or by pressing the Return or Enter key on Xyour keyboard). If there are any errors, a diagnostic message will appear Xjust below the function. Whenever a search function has been successfully Xcompiled, the message will read <no compile errors>. Each time a function Xis successfully compiled, xephem updates all fields and evaluates the Xfunction. As explained below, this can be used as a sort of "astronomical Xcalculator" even when not actually searching. X XSelecting a search goal: X XYou may choose from any of three evaluation algorithms, as selected by the Xtrio of radio buttons. "Find extreme" will search for a maxima or minima of Xthe function. "Find 0" will search for a time when the function evaluates to Xzero. "Binary" will keep incrementing time by "Step Size" (in the main Xmenu) until the state of the function changes, then do a binary search to Xfind the exact time when the function changes state. Binary search Xinterprets a function that evaluates to zero to be in one state and all Xother values to be the opposite state. Generally, binary functions are Xcomprised of logical operators at their outermost expression levels. X XSpecifying the desired accuracy: X XSearching will automatically stop when the time changes by less than the the Xaccuracy value. Note that this method of detecting convergence is not based Xon the value of the search function itself. To change the desired accuracy Xpress the pushbutton showing the current accuracy next to the "Accuracy" Xlabel and enter a new value in the dialog. X XPerforming the search: X XOnce the function is defined and it compiles without errors, you may enable Xsearching by selecting the button at the top labeled "Searching is Active". XThen, each time "Update" is selected on the main menu the search proceeds until Xeither "N Steps" iterations have occurred or until "Step Size" becomes less Xthan Accuracy. The initial search time and step size are set from the main Xmenu, and are adjusted automatically as the search proceeds. Note that by Xsetting "N Steps" to 1 and repeatedly selecting Update you can effectively Xsingle-step the search process. Search control will automatically turn off when Xconvergence is detected, the function is edited or you may turn it off manually Xat any time by toggling the button labeled "Search is Active" back off. X XAdditional notes on searching: X XWhen selecting fields for plotting or listing a button appears labeled "Use Xfor plotting". You may select this button to use the evaluated search Xfunction as an item in the plot or listing feature. Note that the search Xfunction may be used in plotting and listing whether or not searching is Xenabled. X XThe menus that contain each of the fields used in the search function need Xnot be visible for the fields to used for searching. X XThe "Close" button removes the search control menu from the screen; it does Xnot effect actual search operation in any way. X XA successfully compiled search function is evaluated each time xephem updates. XWhenever a search function is compiled it is also evaluated using freshly Xupdated values. In this way, the Search menu can actually be used as an Xarbitrary "astronomical calculator" at any time. In each of these cases you Xneed not be actually `searching' to use these feature. X XHint: X XSearching periodic functions can lead to solutions far from the intended Xrange. You will get best results if you can start the search near the Xexpected answer and with a small step size that bounds the solution. You can Xuse the plotting feature to study a function and get an idea of the Xsolution, then use the automatic searching feature to zero in. X@Data Table XThis is a table of information about each planet, Sol, Luna, and any two Xuser defined objects, ObjX and ObjY. Each data item occupies one column in Xthe table and each object occupies one row. X XSelect the "Setup" button to configure the table rows and columns as Xdesired. The initial configuration can be set from the X resources XDataSelRows and DataSelMiscCols. See the sample XEphem.ad resource file for Xexamples. X XWhen any columns related to rising or setting are active boxes at the bottom Xwill indicate whether the Standard or Adaptive refraction model is in Xeffect and whether the times refer to the center or the upper limb of the Xobject. Similarly, when any of the separation columns are active a box will Xbe present to indicate whether the separation is from a geocentric or Xtopocentric point of view. See the help for the "Setup" menu for more Xinformation about these modes. X XVarious odd ball rising, transit and setting conditions are accounted for Xand marked as follows when they occur: X X NoRise up some time but never rises, as such, today. X NoSet up some time but never sets, as such, today. X NoTran up some time but doesn't transit, as such, today. X CirPol object is circumpolar (never goes below horizon) today. X NvrUp object is never up today. X XX:XX+ "+" appended to rise, transit or set times means the event occurs X twice today; the time given is the time of the first event. X "+" appended to "Hours Up" means it is still up at midnight. X XAny of the information in this table may be plotted, listed or used in a Xsearch algorithm. See the help for these control functions for more details. X XSee the help for the "Setup" menu for a description of each field. X@DataSelection Table XThis menu lets you configure which rows and columns will be in the Data XTable. When this menu first comes up it will be set to indicate the state Xof the Data Table. You may then manipulate the toggle buttons as desired. To Xactually change the Data Table to a new configuration select the "Apply" Xbutton. "Ok" does the same thing but also closes this menu. "Close" just Xcloses this menu without making any permanent changes. In addition to Xmanipulating each item individually, each columns includes handy shortcut Xcontrols at the top to make changes to column as a whole. X XThe first column of this menu selects which rows will be present in the Data XTable. The planets and the sun and moon are always in this column. If user Xdefined objects ObjX or ObjY are defined then they will also be present and Xcontrollable from this column. See the help for the "ObjX/Y" menu for more Xinformation about user defined objects. X XEntries in the remaining three columns in this menu control which columns Xwill be present in the Data Table. They are grouped into three categories Xfor convenience. X XColumn two controls miscellaneous basic information. The descriptions of Xeach entry are as follows: X X Cns name of the constellation in which the object appears. X R_A apparent geocentric right ascension of object, precessed to X given epoch, in hours, minutes and decimal minutes. X Dec apparent geocentric declination of object, precessed to X given epoch, in degrees and minutes. X Az degrees eastward of true north for object. X Alt degrees up from a horizontal plane that is Elevation feet above X sea level. X HeLong true heliocentric longitude, in degrees. Earth's is displayed X on the sun's line. For the moon this is the geocentric X longitude. X HeLat true heliocentric latitude, in degrees. For the moon this is X the geocentric latitude. X EaDst true distance from Earth center to object center, in AU, except X distance to the moon is in miles or km depending on the Units X preference. X SnDst true distance from sun center to object center, in AU. X Elong spherical angular separation between sun and given object, X calculated from the their geocentric ecliptic coordinates. X Note this is not just the difference in ecliptic longitude. X The sign, however, is simply sign(obj's longitude - sun's X longitude), ie, degrees east. thus, a positive elongation X means the object rises after the sun. This field is not X generally useful in searching for conjunctions because of X the discontinuous sign change that occurs at conjunction. X Size angular size of object, in arc seconds. X VMag visual magnitude of object. X Phase percent of visible surface in sunlight. Note the moon phase X is calculated simplistically as just abs(elongation)/180*100 X which can be a few degrees off... this means that because of X how elongation is defined it doesn't say 0 during new moon X (or 100 during full) except during close eclipses (maybe X that's a "feature"?). X XColumn three controls information related to rising, transiting, and Xsetting. These may be computed according to two options. X X"StdRefr", which stands for "standard refraction", computes rising and setting Xbased on the standard horizon refraction of 32 arc minutes. This agrees well Xwill standard publications. "AdpRefr", which stands for "adaptive refraction", Xcomputes rising and setting based on a refraction model that used the actual Xatmospheric and topocentric circumstances displayed on the Main menu. This Xgenerally leads to accuracies well within one minute if all conditions are Xcarefully entered. X X"Limb" means that the rise and set circumstances are based on the location Xof the upper limb of the object. "Center" means that the circumstances are Xbased on the location of the center of the object. (In fact, these allowances Xare only taken into account for the Sun and moon.) X XFollows is a description of the Data Table columns controlled by the third XData Selection column: X X RiseTm X RiseAz The local time and azimuth when the upper limb (or center) of the X object rises today. X TrnTm X TrnAlt The local time and altitude when the object crosses the meridian X today, ie, when its azimuth is true south or, if no precession, when X the local sidereal time equals the object's right ascension. X SetTm X SetAz The local time and azimuth when the upper limb (or center) of the X object sets today. X HrsUp The number of hours the object is up today, that is, the difference X between the set and rise times. X XNote that these times are for the current local day. See the description of X"odd ball" circumstances that this definition can produce and how xephem Xreports them. X XThe last column in the Data Table setup menu controls for which objects Xangular separation is computed. Each entry in the Data Table will be the Xangular separations between each pair of objects, in degrees. X XThe vantage point for the Separation values may be chosen. "Geocentric" Xignores local conditions and gives the separation as seen from Earth Xcenter. "Topocentric" uses the local conditions known to xephem. The Xchoice is particularly critical for lunar occultations, but the effect can Xbe significant for the planets. Geocentric separations between objects and Xthe sun will match the magnitude of the elongation given in the Data menu. X XWhen ObjX or ObjY are defined, these will appear in the last column and Xseparations between them and the other objects (in column 1) may be selected Xfor display. X XNote: X XSearching over a period that will include the rise or set times of either Xobject is generally better performed from the geocentric viewpoint. The Xrefraction effect of the topocentric viewpoint causes many arcminutes of Xrapid whiplash displacement as the objects rise and set that overlays the Xsmooth celestial motion of the objects. This rapid position variation can Xconfuse the solver algorithms that expect fairly smooth functions. X@Mars XThis menu displays the central meridian longitude of Mars, that is, the XMartian meridian currently facing towards Earth. This value may be selected Xfor plotting, listing and searching as described in the help for these Xfunctions. X XAlso included in this menu is a simple schematic display of the Martian Xsurface at the current time. I would like to find a map with a bit more Xdetail. X X@Earth XThis menu displays a simple map of the Earth oriented so that the subsolar Xpoint is centered. The subsolar point is the location on the Earth from which Xthe sun appears to be directly overhead. Another way to interpret the display Xis to think of it as displaying exactly that portion of the Earth currently in Xsunlight. The subsolar point is marked with a cross. X XThe latitude and longitude of the current subsolar point are displayed and may Xbe selected for plotting, listing or searching as described in the help for Xthose functions. X XIt is interesting to set the step size to a few integral number of days and Xwatch the change in latitude. Plotting latitude vs. longitude over the Xcourse of a year is equivalent to plotting the analemma. X XRemember that the numeric information is not updated while looping with Pause Xset to 0. X@Sky View XThis menu displays each object currently loaded in the xephem database with Xseveral display options, subject to filtering by type and magnitude range. The Xcentral display is intended to be similar to a telescopic view. Descriptions Xof each function are keyed to the schematic depiction below: X X _____________________________________________ X |Alt-Az | | [Alt] [Az] | | X |RA-Dec | F | | A | X |--------| O | | l | X |Grid | V | | t | X |--------| | | | X |F Mag | | | / | X |B Mag | | Sky | | X |--------| | | D | X |Dots | | | e | X |Ecliptic| | | c | X |Labels | | | | X |--------| | | | X |Locate | | | | X |--------| | [RA] [Dec] | | X | |___|__________________________|___| X | | Az / RA | X | |__________________________________| X | | Date/Time stamp | X |________|__________________________________| X | Filter Close Help | X |___________________________________________| X XAlt-Az / RA-Dec X The radio box in the upper left corner selects whether the display X coordinate system is Altitude-Azimuth or Right Ascension-Declination. X Whenever the Alt-Az system is used, nothing is displayed that would lie X below the current horizon (except trails; see note under Sky). X X The orientation of the display circle is always without reflections. In X Alt-Az mode, left, right, up and down as are they would appear to the X otherwise unaided eye. In RA-Dec mode, up is always celestial north, left X is always celestial East. The meridian named by the horizontal slider is X always the line between the center of the field-of-view and the nearest X pole. X XGrid X The toggle button labeled "Grid" controls whether a calibration grid will X overlay the display. When the grid is displayed, its graduation is displayed X below the toggle button. X XF Mag / B Mag X The two sliders on the left set the brightness range being displayed. Only X objects that are currently within the selected range will be shown on the X display. Note that sliding either scale beyond its opposite is not permitted X but it is permitted to do this by selecting in the slider trough should you X really want to do this (to turn off all objects). X X Note this does not effect trails. X XDots X The toggle on the left labeled "Just Dots" selects how objects are drawn. X X When the toggle is pushed in, objects of all types are displayed simply as X dots. The diameter of the dots equals the difference between its magnitude X and the faintest magnitude. In this way the size of the dots can be changed X as desired. X X When the toggle is released, each type of object is displayed with a unique X schematic symbol. These symbols may be viewed from the Filter menu. In this X case too the size is proportional to magnitude above the faintest limit. X X In either form, the color of the object is displayed according to the value X established for each basic type in the X resource database. See the sample X XEphem.ad resource file for examples of setting object colors. X XEcliptic X The toggle on the left labeled "Ecliptic" selects whether a dotted line is X drawn along the ecliptic. The ecliptic is the plane of the Earth's orbit X or, as seen from Earth, the path of the Sun and the approximate path X of the planets across the sky. X XLabels X The toggle on the left labeled "All labels" controls whether the labels X for all objects are forced on. This does not effect which objects have X their individual "Persistent label" options on. X XLocate X The button labeled "Locate..." will pop up a list of the basic objects and X the defined user defined objects, if any. Selecting any of these entries X will place a cross-hair over the object. If the object is not within the X field of view the object will first be centered, unless Alt-Az mode is X currently active and the object is below the horizon. To locate other X objects use the ObjX/Y menu. X XFOV X The left vertically-oriented slider controls the field-of-view of the X display circle. This can be varied from 1 to 180 degrees. X X[Alt] [Az] [RA] [Dec] X The coordinates of the cursor are tracked and displayed across the bottom X and top of the circular display area as long as it is within the circle and X the left mouse button is depressed. X X NOTE: The values displayed during tracking for the coordinate system X opposite to the one currently in effect may not agree exactly with X the values displayed elsewhere by xephem, particularly for close solar X system objects. To understand why recall that in all these other displays X xephem computes geocentric RA/Dec and topocentric Alt/Az. Recall further X that parallax contributes significantly to the difference between these X points of view and parallax depends on the distance to each particular X object. Thus, there is no single transformation between these coordinate X systems that is correct for all objects. During tracking, the transformation X to the coordinate system opposite to the one in current use by the Sky View X display is computed without regard to parallax; this is strictly correct X only for objects very far away. This has the useful result that while in X RA/Dec coordinate mode the tracking values for Alt/Az may be thought of as X being geocentric; and while in Alt/Az mode, RA/Dec will be topocentric. X XSky X The center circular area is the sky display of objects. Follows is a X description of the operations that may be performed in this area using the X pointer. X X If the pointer is placed near a visible object and the third button is X pushed, a popup will appear. This will present several basic data for the X object. This data is exactly the same as that which is available in the X Data Table menu; see it's Help for more information. If a trailed object is X selected, the data will be as it was at the time the position was created. X In addition, the popup offers several control operations, as follows: X X Selecting "Point" from the popup will center the object in the field of X view (as well as can be done with the accuracy of the pointing scales X anyway). X X Selecting "Make ObjX/Y" will assign the given object to become ObjX X or ObjY, depending on which one is currently being displayed in the X ObjX/Y menu. See the help for the ObjX/Y menu for more information on X that menu. X X Selecting "Leave Trail" will start to accumulate all positions of the X given object as time is advanced. Each new location will be connected X with a line to its previous location. The trails remain correct if the X display coordinate system is changed. Trails may be turned on or off X without loss of trail information. However, trailing information is X discarded if trailing is turned off when a new time step is performed. X If any point in a trail is selected the information displayed is as per X the object at that time. The fastest way to accumulate trailing X information is to turn trailing on and pop the menu down while running. X X Note that in Alt-Az mode, if an object goes below the horizon the line X segments of the trail are displayed but not the actual points. X X Selecting "Persistent Label" will place the name of the object near it X on the display. This will remain until the label is turned off. Note X this option is maintained separately for trailed objects and for X the untrailed objects; that is, you have independent control over X labeling for a trailed object and its currently displayed object X since the latter also always appears in the trailed list. X X The coordinates of the cursor are displayed in the corners of the circular X sky area as long as the cursor is within the central circle and the left X mouse button is depressed. X XAlt / Dec X The right vertically-oriented slider controls one of two axes that X defines the direction in which the display points. In Alt-Az mode this X controls altitude and can be varied from 0 to 90 degrees. In RA-Dec mode X this controls Declination and can be varied from -90 to +90. X XAz / RA X The bottom horizontally-oriented slider controls one of two axes that X defines the direction in which the display points. In Alt-Az mode this X controls azimuth and can be varied from 0 to 359 degrees. Azimuth 0 is X north and increases eastward. In RA-Dec mode this controls Right Ascension X and can be varied from 0 to 23.9 hours. X XDate/Time Stamp X This displays the date and time for which the display is valid. X XFilter X The Filter button along the bottom brings up a menu that controls X whether classes of objects are displayed. Using the Filter menu, one may X select which classes of objects are desired. Selecting "Apply" updates X the sky display according to the desired selection. Selecting "Ok" does X the same thing but also closes the filter menu. X X For reference, the Filter menu also contains the schematic symbol for each X type of object, and its code when used in a database file. X@Solar System View XThis is a graphical representation of the solar system. The Sun is always at Xthe center of the screen, marked as a plus (+). X XThe three sliders at the edges control the position of the observer. The Xvertical slider on the left controls the distance from the sun -- you are Xcloser as the slider is slid further up. The horizontal slider under the Xview controls the heliocentric longitude -- think of it as a rotation about Xthe central axis. The vertical slider on the right controls the heliocentric Xlatitude -- your angle above the ecliptic plane. X XAny feature may be identified by pointing near it and clicking the right Xmouse button. This will bring down a temporary popup menu with additional Xinformation until the button is released. The RA/Dec given for the Earth is Xthat of the sun. All RA/Dec info displayed is for the epoch as it was set Xon the Main menu when the dot was computed. X XThe "Leave trails" option can be used to retain old dots. By turning on the X"Connect dots" option, these dots are connected by line segments. The Xfastest way to accumulate lengthy trail operation is to turn on trailing Xand run with the menu popped down. X XThe planets may be individually turned on and off, without loss of any Xdisplay data associated with them, by using the toggle panel near the Xbottom. If ObjX or ObjY are defined and are solar system objects then they Xwill appear on the display and in the list. X XThe bottom button marked "Stereo" is used to bring up another image of the Xsolar system from a slightly displaced vantage point. Adjusting your gaze to Xfuse the two images together will reveal a 3D image. This effect is most Xpronounced if trails have been turned for a significant portion of the Xorbits of the objects of interest. This effect was designed primarily to Xhelp visual the orbits of comets. X XAt the bottom of the stereo display is a slider to control the location of Xthe second vantage point. When the slider is in the center both views are Xidentical. Moving the slider to the left will display the scene as though Xthe viewer has moved such as to move the objects to the left. Objects closer Xto the viewer move more. Moving the slider to the right does the same but in Xthe opposite direction. In this way, you may adjust the stereo effect to be Xmost comfortable to you, and with or without requiring crossed eyes. X XClosing the main Solar System menu will close both it and the Stereo menu, XIf the Solar System menu is closed while the Stereo menu is on, it will Xreappear when the Solar System menu is reactivated. if it is up. X@DataBase menu XThis menu allows you to inspect and modify the collection of objects that Xare currently in memory. These objects form what is referred to as the Xxephem database. X XThe top portion of the menu displays a count of each major type of object in Xthe database. X XXephem supports files that contain descriptions of objects. These files may Xbe read into memory either adding to the current database or replacing it. XEnter the name of the desired xephem database file in the text area provided Xthen select either "Append" or "Replace", respectively. X XThe default database filename may be specified by setting the X resource Xnamed "XEphem*DBPromptD.textString". The internal default name is X"ephem.db". The xephem distribution kit includes a sample ephem.db that Xcontains more than 15,000 objects of all types. X XAlso available from the author is the entire Smithsonian Astrophysical XObservatory star list. These have been sorted into ten sky regions. There is Xone file per region. The entire set is some 11MB. X XFollows is a description of the format of these database files. This format Xremains compatible with the "ephem" dumb-terminal version of xephem for Xthose interested. X XNote that the "Filter" menu accessible from the "Sky View" menu also includes Xa list of the type codes for each object, for easy reference. X X Each object occupies one line. Fields are separated with commas. Some fields X are further subdivided into subfields with vertical bars (|). Lines X beginning with anything other than a-z, A-Z or 0-9 are ignored and may be X used for comets. Objects may be in any order. X X Where they appear, all date fields may be in either of two forms: X X 1) month/day/year, where day may contain a trailing decimal portion. X examples: 1/1/1993 and 1/1.234/1993 X NOTE: this is always the format of dates in database files, regardless of X the current xephem run-time Data format preference setting. X X 2) a real-number, such as 1993.123. X X The first two fields are always Name and Type. Remaining fields depend on the X form of the object's motion. X X The Name field is the object's name. X X The Type field always starts with a single letter designating the form of X the object's motion: X f: fixed (no proper motion) X e: heliocentric elliptical orbit X h: heliocentric hyperbolic orbit X p: heliocentric parabolic orbit X X if "Type" is fixed, an object class code may follow in the next subfield: X C: Cluster, globular X U: Cluster, with nebulosity X O: Cluster, open X G: Galaxy, spiral X H: Galaxy, spherical X A: Cluster of galaxies X N: Nebula, bright X F: Nebula, diffuse X K: Nebula, dark X P: Nebula, planetary X Q: Quasar X T: stellar object X B: Star, binary X D: Star, double X M: Star, multiple X S: Star X V: Star, variable X X if class is one of T, B, D, S or V, the spectral class and possibly the X numerical subclass designation may follow in the next subfield: X O, B, A, F, G, K, M, N, C, S X X For other object types, the remaining fields are defined as follows: X X elliptical format (e < 1): X i = inclination, degrees X O = longitude of ascending node, degrees X o = argument of perihelion, degrees X a = mean distance (aka semi-major axis), AU X n = mean daily motion, degrees per day (computed from a**3/2 if omitted) X e = eccentricity, X M = mean anomaly (ie, degrees from perihelion), X E = epoch date (ie, time of M), X D = the equinox year (ie, time of i/O/o). X g/k or H/G = magnitude model; select which by preceding the first field X with either a "g" or an "H"; H/G is the default if neither is given. X s = angular size at 1 AU, arc seconds, optional X X hyperbolic format (e > 1): X T = epoch of perihelion X i = inclination, degrees X O = longitude of ascending node, degrees X o = argument of perihelion, degrees X e = eccentricity, X q = perihelion distance, AU X D = the equinox year (ie, time of i/O/o). X g/k = magnitude model X s = angular size at 1 AU, arc seconds, optional X X parabolic format (e == 1): X T = epoch of perihelion X i = inclination, degrees X o = argument of perihelion, degrees X q = perihelion distance, AU X O = longitude of ascending node, degrees X D = the equinox year (ie, time of i/O/o). X g/k = magnitude model X s = angular size at 1 AU, arc seconds, optional X X fixed format: X RA, hours X Declination, degrees X magnitude X reference epoch X s = angular size, arc minutes, optional X@Object XXephem supports two user-defined objects, denoted ObjX and ObjY. These may Xbe fixed objects or objects in elliptical, hyperbolic or parabolic Xheliocentric orbits. The ObjX/Y dialog allows you to define these objects. X XXephem maintains a working copy of these objects for use with the ObjX/Y Xmenu that is separate from the real ObjX and ObjY. The ObjX/Y menu always Xworks on these working copies. The working copies and the real ObjX/Y only Xinteract when using the Ok, Apply and Reset control, as described shortly. X XThe ObjX/Y menu is always displaying information from one or the other of Xthese working copies as indicated by the small radio box in the center of Xthe menu at the top. This box may also be used to changed whether ObjX or XObjY is being displayed and manipulated. We will refer to the one selected Xas the "current working object." X XThe radio box in the upper left displays the basic type of the current Xworking object. This can be changed by selecting another of the collection Xof toggle buttons. X XIn the left and center of the menu is an area that lists each field for the Xcurrent working object and its present value. The list is adjusted to Xcorrespond to the fields that are associated with the type of the current Xworking object. These fields may be changed by selecting the button that Xcontains their value. This will bring up a small text entry dialog. A new Xentry may be typed into the dialog box and applied by hitting RETURN or Xselecting the "Ok" button. The value may be left unchanged by selecting X"Cancel". X XAlong the right edge of the ObjX/Y menu is a list of each object currently Xloaded into the xephem database. (See the Help for the "Data Base" menu for Xmore information on manipulating this data base.) If there are more than 20 Xitems then a scroll bar may be used to browse through the list. The entries Xare sorted in numeric and alphabetic order for easy selection. If one of Xthese objects is selected, then it is copied to the current working object. XYou may then further edit the values for this working object as desired. X XWhen the current working object is as you want it, select "Apply" to copy it Xthe real ObjX (or ObjY) used throughout the other functions of xephem. "Ok" Xwill do the same thing and also close the ObjX/Y menu. X XSelecting "Reset" will load the current working object with a copy of the Xreal ObjX (or ObjY). X XSelecting "Sky Point" will move the center of the field of view on the "Sky XView" menu so that the current working object is centered and a cross-hair Xis drawn over the object. This change in pointing direction and marking will Xtake place even if the object is not in the Sky View type filter or within Xthe magnitude range. Note that the Sky View display will _not_ be changed if Xit is set to Alt-Az mode and the current working object is below the Xhorizon. X XSelecting "Sky Mark" will draw a cross-hair on the Sky View menu at the Xlocation of the current working object if it is within the Sky View field of Xview. The Sky View menu is never reaimed with this command. X XFollows is a description of each field for the type of the current working Xobject. To get a description of the fields for other types of objects, Xchange the type of the current working object and reselect Help. X X@Fixed Object X+Object XFixed objects are characterized by five parameters: X X RA, X Dec, X magnitude, X the reference epoch for the coordinates and X angular size in arc seconds, optional X XNote: X XIn order to conserve memory usage, xephem stores the RA and Dec for a fixed Xobject only once with each object. These values are always precessed _in Xplace_ to the current display epoch. Thus, you will find that the RA and Dec Xdisplayed for a given object may change if the epoch is changed on the main Xmenu and the object information is redisplayed here on the ObjX/Y menu. X@Elliptical Object X+Object XElliptical objects are characterized by 12 parameters: the parameters that Xdefine a heliocentric elliptic orbit and the coefficients for either of two Xmagnitude models. These elements are the same ones often listed in the XAstronomical Almanac. The elements are, in order: X X i = inclination, degrees X O = longitude of ascending node, degrees X o = argument of perihelion, degrees X a = mean distance (aka semi-major axis), AU X n = mean daily motion, degrees per day X e = eccentricity X M = mean anomaly (ie, degrees from perihelion) X E = epoch date (ie, time of M) X D = the equinox year (ie, time of i/O/o) X g/k or H/G = either of two magnitude models; see below X s = angular size at 1 AU, arc seconds, optional X X XYou might have other parameters available that can be converted into these. XThe following relationships might be useful: X X P = sqrt(a*a*a) X p = O + o X n = 0.9856076686/P X T = E - M/n X q = a*(1-e) X AU = 149,597,870 km = 92,955,621 U.S. statute miles X where X P = the orbital period, years; X p = longitude of perihelion, degrees X T = epoch of perihelion (add multiples of P for desired range) X q = perihelion distance, AU X XNote that if you know T you can then set E = T and M = 0. X XXephem supports two different magnitude models for elliptical objects. One, Xdenoted here as g/k, is generally used for comets in elliptical objects. The Xother, denoted H/G, is generally used for asteroids in the Astronomical XAlmanac. X X+OBJXY_gkMAGNITUDE XWhen using this model for elliptical objects, the first of the two magnitude Xfields must be preceded by a letter "g". This applies in both the ephem.db Xdatabase file and the corresponding menu elliptical object definition prompt; Xotherwise the default magnitude model for elliptical objects is the H/G model. X X+OBJXY_HGMAGNITUDE X XThe H/G model is the default magnitude model for elliptical objects but it can Xalso be explicitly indicated when the first of the two magnitude fields is Xpreceded by a letter "H". This works in both the ephem.db database file and the Xcorresponding menu elliptical object definition prompt. X@Hyperbolic Object X+Object XHyperbolic objects are characterized by 10 parameters: the parameters that Xdefine a heliocentric hyperbolic orbit and the magnitude model coefficients. XThese orbital parameters are, in order: X X T = epoch of perihelion X i = inclination, degrees X O = longitude of ascending node, degrees X o = argument of perihelion, degrees X e = eccentricity, X q = perihelion distance, AU X D = the equinox year (ie, time of i/O/o). X g/k = magnitude model X s = angular size at 1 AU, arc seconds, optional X XAs with elliptical elements, other parameters might be available. The Xrelationships are generally the same, except for: X X q = a*(e-1) X X+OBJXY_gkMAGNITUDE X@Parabolic Object X+Object XParabolic objects are characterized by 9 parameters: the parameters that Xdefine a heliocentric parabolic orbit and the magnitude model coefficients. XThese orbital parameters are, in order: X X T = epoch of perihelion X i = inclination, degrees X o = argument of perihelion, degrees X q = perihelion distance, AU X O = longitude of ascending node, degrees X D = the equinox year (ie, time of i/O/o). X g/k = magnitude model X s = angular size at 1 AU, arc seconds, optional X X+OBJXY_gkMAGNITUDE X@OBJXY_gkMAGNITUDE XThe g/k magnitude model requires two parameters to be specified. One, the Xabsolute magnitude, g, is the visual magnitude of the object if it were one XAU from both the sun and the earth. The other, the luminosity index, k, Xcharacterizes the brightness change of the object as a function of its Xdistance from the sun. This is generally zero, or very small, for inactive Xobjects like asteroids. The model may be expressed as: X X m = g + 5*log10(D) + 2.5*k*log10(r) X where: X m = resulting visual magnitude; X g = absolute visual magnitude; X D = comet-earth distance, in AU; X k = luminosity index; and X r = comet-sun distance. X XNote that this model does not take into account the phase angle of sunlight. X X@OBJXY_HGMAGNITUDE XThe H/G model also requires two parameters. The first, H, is the magnitude of Xthe object when one AU from the sun and the earth. The other, G, attempts to Xmodel the reflection characteristics of a passive surface, such as an Xasteroid. The model may be expressed with the following code fragment: X X beta = acos((rp*rp + rho*rho - rsn*rsn)/ (2*rp*rho)); X psi_t = exp(log(tan(beta/2.0))*0.63); X Psi_1 = exp(-3.33*psi_t); X psi_t = exp(log(tan(beta/2.0))*1.22); X Psi_2 = exp(-1.87*psi_t); X m = H + 5.0*log10(rp*rho) - 2.5*log10((1-G)*Psi_1 + G*Psi_2); X where: X m = resulting visual magnitude X rp = distance from sun to object X rho = distance from earth to object X rsn = distance from sun to earth X XNote that this model does not take into account the phase angle of sunlight. END_OF_FILE if test 65231 -ne `wc -c <'xephem.hlp'`; then echo shar: \"'xephem.hlp'\" unpacked with wrong size! fi # end of 'xephem.hlp' fi echo shar: End of archive 4 $of 21$. cp /dev/null ark4isdone MISSING="" for I in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 ; do if test ! -f ark${I}isdone ; then MISSING="${MISSING} ${I}" fi done if test "${MISSING}" = "" ; then echo You have unpacked all 21 archives. rm -f ark[1-9]isdone ark[1-9][0-9]isdone echo Building ephem.db cat > ephem.db.Z.uu ephem.db.Z.uu.? uudecode ephem.db.Z.uu rm ephem.db.Z.uu ephem.db.Z.uu.? uncompress ephem.db.Z echo Building skyviewmenu.c cat > skyviewmenu.c skyviewmenu.c.? rm skyviewmenu.c.? echo Building smallfm.xbm cat > smallfm.xbm smallfm.xbm.? rm smallfm.xbm.? else echo You still must unpack the following archives: echo " " ${MISSING} fi exit 0 exit 0 # Just in case... -- // chris@IMD.Sterling.COM | Send comp.sources.x submissions to: \X/ Amiga - The only way to fly! | "It's intuitively obvious to the most | sources-x@imd.sterling.com casual observer..." |