xephem

     Name
          xephem - an interactive astronomical ephemeris for X

     Syntax
          xephem

     Description
          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.


     Main Menu
          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.


     Resources
          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.

     Author
          Elwood Downey, currently at
          ecdowney@pobox.cca.cr.rockwell.com

     See also
          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.