Xephem is an interactive astronomical ephemeris program for X Windows. It has built-in support for all planets plus support for arbitrary objects given their heliocentric orbital elements. Xephem generates tabular and graphical schematic views of the sky and solar system objects, can plot and list data, and can search for arbitrary user-defined circumstances.
Xephem contains extensive context-senstive on-line help. Virtually none of that help is duplicated here so go ahead and run xephem to learn more. In order for xephem to find this help text the resource `XEphem.HELPFILE' must be set to the pathname of the xephem.hlp file.
The main menu of xephem provides control and display of three basic services: observing circumstances, looping, and access to additional displays.
Observing circumstances includes location, time and atmospheric conditions (used for the refraction model). Looping refers to the ability to set xephem so that it automatically increments time and a desired step size and rate. The additional displays provide all of the tabular and graphical information available, and always refer to the circumstances defined in the main menu. The additional displays are activated from the Views pulldown.
Xephem has information about the Solar system planets and several moons built in. These can be accessed without the need to access an external database. However, if a database of objects is available then xephem can read this information into memory and use it as well. The database is read in using the DB... pulldown. The objects may be inspected in detail, manipulated and assigned to so-called `user defined objects' X and Y using the ObjX/Y... pulldown.
All of the tabular data that xephem presents can be written to a file and later plotted, written in a tabular listing, or used to formulate an arbitrary mathematical expression that can be solved for a maximum, minimum or zero. All of these facilities are accessed from the Control pulldown.
Several display and accuracy formating options may be controlled from the Preferences pulldown.
Finally, the Help pulldown provides several categories of assistance applicable to the overall operation of xephem. Beginners might start by reading the Introduction help section.
XEphem has many resources, many of which you will soon want to tune to your taste and circumstances; many others may be left unchanged. Look through the XEphem.ad distribution for full details.
Of course, in addition to all the custom resources, xephem supports the usual Xt resources such as -display, -xrm, -fg and -bg.
The application class of xephem is XEphem.
A list of widgets in xephem would be enormous. If you really want such a list, build xephem for X11R5 and use the editres feature. The necessary code is in xephem.c surrounded by #ifdef WANT_EDITRES.
Elwood Downey, currently at ecdowney@pobox.cca.cr.rockwell.com
Ephem, the ancestor of xephem suitable for "dumb" 24x80 character displays, including VMS and DOS as well as UNIX.
Ephem and xephem are both on export.lcs.mit.edu; look for contrib/ephem* and contrib/xephem* for the latest releases.