XEphem – Serious Interactive Astronomical Software Ephemeris

Last Updated on April 9, 2026

XEphem is a Motif based ephemeris and planetarium program for Unix-like operating systems including Linux.

This is free and open source software.

Key Features

• Computes heliocentric, geocentric and topocentric information for all objects.
• Built-in support for all planets; the moons of Mars, Jupiter, Saturn, Uranus and Earth; central.
• Meridian longitude of Mars and Jupiter; Saturn’s rings; and Jupiter’s Great Red Spot.
• Allows user-defined objects including stars, deepsky objects, asteroids, comets and Earth satellites.
• Provides special efficient handling of large catalogs including Tycho, Hipparcos, GSC.
• Displays data in configurable tabular formats in conjunction with several interactive graphical views.
• Displays a night-at-a-glance 24 hour graphic showing when any selected objects are up.
• Displays 3-D stereo Solar System views that are particularly well suited for visualizing comet trajectories.
• Quickly finds all close pairs of objects in the sky.
• Sorts and prints all catalogs with very flexible criteria for creating custom observing lists.
• Creates plots of any pairs of all data fields throughout the program.
• Downloads current asteroid and comets ephemerides from Lowell Observatory and Minor Planet Center.
• Downloads timely Earth satellite orbital TLE parameters.
• Plots true binary system orbits.
• Downloads Digitized Sky Survey FITS files from STScI or ESO.
• Provides a handy coordinates spreadsheet for converting among equatorial, ecliptic, horizon and galactic frames.
• Displays live SOHO images of the Sun.
• Includes a compiler for entering and solving user-written functions using any data fields.
• Serves as the control point for GOTO telescopes such as Meade LX200 or other external applications.
• Displays FITS files images overlaid with database symbols and other graphical information.
• Performs automatic star pattern matching to automatically solve for World Coordinate System on any image.
• Performs 1-click 2D Gaussian relative and absolute photometry.
• Defines and saves any number of Eyepieces to use in sky maps.
• Captures, displays and clips to any number of local horizon profiles.
• Stores sets of all Sky View options in history sets for easy playback later.
• Prints using high quality Postscript.
• Allows you to assign any number of objects as Favorites for special fast access throughout the program, and makes them available even when their original databases are no longer loaded.
• Provides an extensible image gallery initialized with over 300 beautiful and informative color images of deep sky objects.
• Provides an observing logbook which is automatically filled in with observing circumstances, with searching on most fields.
• Displays magnetic deviation for any location.
• Create movie loops of any View, NAAG or Plot window.

Website: github.com/XEphem/XEphem
Support:
Developer: Elwood Charles Downey
License: MIT License

The image above shows the program’s Sky View, a schematic representation of the sky showing database objects and useful auxiliary information. A FITS file image can also be displayed simultaneously.

XEphem is written in C. Learn C with our recommended free books and free tutorials.

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