Name

XEphem - an interactive astronomical ephemeris for X11

Syntax

xephem [-prfb] [-install {yes|no|guess}] [-resfile <resourcefile>] [-[no]splash]

Description

XEphem is an interactive astronomical ephemeris program for the X Window System. It provides many graphical views as well as quantitative heliocentric, geocentric and topocentric information for Earth satellites, solar system and celestial objects.

XEphem primarily uses two directories at runtime. One is referred to as the Shared directory, the other as the Private directory. Shared is read-only and holds supporting files that can be shared among all users on a system. Private is writable and one is expected to exist for each user. See the section below on X Resources for more information about defining these directories.

XEphem contains extensive context-sensitive on-line help. Virtually none of that help is duplicated here so go ahead and run XEphem to learn more. The first thing to do once XEphem is up is configure the browser interface. All of XEphem help is written in html and stored in a file named xephem.html. The first entry in the Help menu brings up a table of browsers and defines a command for each that will invoke the browser and pass it the URL and anchor of the text to display. XEphem comes configured to support several different browsers. If yours is listed, just click the button to its left and your help system should be working. If your browser is not listed, please check the FAQ for the latest news.

Note that if you are running XEphem under cygwin on Windows, before starting XEphem set an environment variable XEHELPURL to the full path of the xephem.html file on your system using Windows path syntax (not cygwin paths). This file is in the help directory within the source directory of the master distribution. After this is in the place, run xephem and it can use MS IE to display help.

The XEphem Main window is the master panel for setting up observing circumstances, time looping, and for accessing all the additional tools and displays. Observing circumstances includes location, date, time, local magnetic deviation and atmospheric conditions (used for the refraction model). Looping provides the ability to set up XEphem so that it automatically increments time at a desired step size and rate. Additional displays provide all of the graphical and quantitative information available, which are always computed with respect to the circumstances defined in the Main menu. Tools provide access to plotting, searching, AAVSO and much more.

Command line Options

-prfb displays all the built-in default resources, then exits. Some of them are described here.

-install controls whether XEphem will install a private colormap. Without this option XEphem will try to decide automatically whether it is necessary. To force using a private colormap, use -install yes. To prevent it, use -install no. The default automatic behavior is equivalent to -install guess.

-resfile <resourcefile> tells XEphem to use an alternate file for initial resource settings. See below for the default situation.

-splash or -nosplash controls whether XEphem will display a progress window front and center while it is coming up. The choice is yours because this can be a useful sign of life on a slow system, or be the source of an annoying flash on a fast system. The setting is persistent so it will remain until changed.

Menu Tour

File

This menu controls access to the System log; setting up network access; accessing the gallery; displaying a progress meter; controlling time and location information remotely; and keyboard accelerators for time stepping.

View

This menu offers several graphical displays if the Sun, Earth, Moon and several planets; a user configurable data table; and Sky and Solar System views.

Tools

This menu gives access to tools which can plot any XEphem data items; save any data items to text files for easy export to other programs; enter an arbitrary function to evaluate and solve using any XEphem data items; access AAVSO online; show the Night at a glance; find close pairs of objects; convert among various astonomical coordinate systems; and a handy log for taking observing notes.

Data

This menu gives control over which objects XEphem will work with. Objects may be created on the fly, read from catalog files, downloaded from the Internet, deleted or searched. A special category of objects known as Field Stars may be configured, which are very large catalogs of objects whose access has been optimized. Any number of Favorite objects may be defined for especially easy access in several other places throughout XEphem.

Preferences

This menu offers several configuration choices and tools for changing fonts and colors used throughout XEphem. These choices can be changed at runtime and saved to disk to become the new defaults.

Help

This menu offers overall information about XEphem; context sensitive help; references; version number and the Copyright statement.

X Resources

When first started, XEphem looks for a file named .xephemrc in your $HOME directory. It should contain one line of the form:

XEphem.PrivateDir: ~/.xephem

This defines the Private directory, where XEphem will store your personal settings. The example line shown here, which is also the assumption if the file is not present, means XEphem will create and use a directory named .xephem for this purpose in your home directory.

Within this directory a text file named XEphem will contain all the Preferences that differ from those built in. One important entry defines the Shared directory. This is in intended for multi-user installations. XEphem looks here for support files. Unless defined otherwise, the Shared directory is ".", that is, the current directory.

Author

Elwood C. Downey, email ecdowney@ClearSkyInstitute.com.

References

The Web homepage, including the FAQ, is maintained at http://www.clearskyinstitute.com/xephem

The online Help entry on Credits lists many of the references, individuals and organizations which have contributed to XEphem.