Table of Contents

## Name

XEphem 3.5 - an interactive astronomical ephemeris for X

## Syntax

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

## Description

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

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 Main window of XEphem provides control and display of three basic services: observing circumstances, looping, and access to additional tools and displays. Observing circumstances includes location, date, time and atmospheric conditions (used for the refraction model). Looping refers to 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, and always refer to the circumstances defined in the main menu. Tools provide access to plotting, searching, AAVSO, Seti@Home and more.

## Options

-prfb displays all the built-in default resources, then exits.

-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.

## Menu Tour

File

This menu controls basic operation, including exiting. When XEphem is first started it may beep. This means a message has been put in the System log dialog, which can be displayed from this menu. Other chores here include setting up network access; displaying a simple progress meter; controlling time and location information remotely, and keyboard accelerators for time stepping.

View

This menu offers several graphical displays if the Earth, Moon and several planets; a user configurable 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; monitor your Seti@Home client; show the Night at a glance; find close pairs of objects; and convert among various astonomical coordinate systems.

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. Up to three User objects may be assigned for especially easy access in several other places throughout XEphem.

Preferences

This menu offers several configuration choices. These will effect the overall appearance or behavior of XEphem. These choices, as well as fonts and colors, 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; several worked examples; references; version number and the Copyright statement.

## X Resources

XEphem initial conditions are defined using a resource file. By default the file is named XEphem located in a directory also called XEphem in your $HOME directory. You should never find the need to edit this by hand because XEphem will manage it when you Save settings.

## Author

Elwood Downey, email ecdowney@ClearSkyInstitute.com.

## References

The latest information about XEphem 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.

Table of Contents

- Name
- Syntax
- Description
- Options
- Menu Tour
- X Resources
- Author
- References