
			Welcome to xephem v2.6

Xephem is an interactive astronomical ephemeris program for X Windows systems. 
It computes heliocentric, geocentric and topocentric information for celestial
objects. Xephem has built-in support for all planets; the moons of Jupiter,
Saturn and Earth and Mars' central meridian longitude. Xephem supports objects
in heliocentric or Earth orbit given the appropriate elements. Sample databases
of over 16000 objects are included in the release kit. Xephem generates data in
configurable tabular forms and in several detailed graphical formats.  Xephem
can plot and list all data fields and can be programmed to search for arbitrary
circumstances. Xephem can serve as the control point for automated telescopes
and can connect to auxiliary database servers in real-time via named streams
pipes (UNIX fifos).


Xephem requires at least X11R4 and OSF/Motif 1.1. Xephem has been built on
many UNIX systems as well as VMS. A list of known ported systems and building
hints may be found in the file INSTALL. A summary of the changes since v2.5
appears at the end of this notice.


There is only a small manual, but there is extensive on-line help. So, the
first thing to do is to build xephem then start selecting the Help buttons.
A good order to read the help entries is the way they are listed in the Help
pulldown off the Main menu. Instructions for building xephem may be found in
the file INSTALL.


Xephem uses several X resources to name supporting files and directories. The
sample X defaults file, XEphem.ad, and the fallback resources in xephem.c, have
these defined relative to this top level directory structure I have included in
this distribution kit. You may want to rearrange things for your installation.
See the file INSTALL for a list of all the files used by xephem at runtime. The
comments throughout XEphem.ad will also help you set up all the X resource
defaults for xephem.




I would like to hear what you think of xephem, good and bad. If you drop me a
quick note I will save your email address and directly send you announcements of
changes. I maintain the master copy of the source on iraf.noao.edu in
contrib/xephem. Check there occasionally for updates and contributed prebuilt
executables. If you would like to contribute an executable, please let me know.

Thank you for your interest in xephem.


Elwood Downey
ecdowney@noao.edu
Januray, 1995



The revision history at the top of versionmenu.c lists all changes since v2.5.
Follows is a summary of these changes:

Sky View:
    add constellation figures and names.
    display angular separation during mouse tracking.
    better support of objects with finite size.
    object trails are now immune to filtering for better comet displays.
    at least 25% faster, much more in some circumstances.
    Skyloc fifo message now includes FOV and Magnitude.
    improved symbols.

Earth View:
    add cylindrical projection (not unlike Mercator).
    mark location of totality during solar eclipses.
    display Local Mean and Sidereal times during mouse tracking.
    improved appearance of trailed objects.
    more than doubled the map resolution.

Database:
    object searches may now be performed by name.
    database now separated into several files, each with .edb extension.
    database files may be selected using a FileSelection box.
    updated database entries for comets, spacecraft, NGC, SAC and asteroids.
    a user-defined set of database files may be read automatically on startup.
    support for supernova remnant object class.
    explicit control over opening the DB fifo.

Time Control:
    new Auto Time Zone mode maintains local changes in savings time.
    time zone names may now be up to 7 characters long.
    new preference to select local or UT times everywhere.
    Pause may now take on fractional values of seconds.

Misc:
    add Movie shortcuts to most views for demos.
    improved accuracy for hyperbolic solar orbits.
    add N/S and E/W flip controls to Sky, Jupiter and Saturn views.
    most views now have controls hidden in pulldown menus.
    rearrangement of distribution directory layout
    improved accuracy of Saturn's moons.
