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XEphem Screenshot.png
Screenshot of the XEphem 3.7.2 with the Earth and sky views
Developer(s)Elwood C. Downey
Initial release1990; 31 years ago (1990) [1]
Stable release
3.7.7[2] / August 9, 2015; 5 years ago (2015-08-09)
Repository Edit this at Wikidata
Operating systemUnix-like
TypeAmateur astronomy/observational astronomy

XEphem is a Motif based ephemeris and planetarium program for Unix-like operating systems developed by Elwood C. Downey.


XEphem started as a Unix and Motif conversion of the IBM PC-based ephem. It was initially released in December 1993 with version 2.5.[citation needed] The most recent stable version is 3.7.6 (2013). XEphem's source code is available, but its free usage is restricted for personal and educational purposes only.[3] The full set of catalogs is only distributed with a purchase of the commercial version.[4]

Algorithms and models[edit]

XEphem uses

and includes

and other specialized catalogs. It also include the Digital Lunar Orbiter Photographic Atlas of the Moon.[7] XEphem is a client for Internet data sources such as the Digitized Sky Survey, Solar and Heliospheric Observatory, AAVSO light curves, and global temperature and cloud coverage. Through the Instrument Neutral Distributed Interface, XEphem can control some models of amateur telescopes, such as by Meade, Celestron, and Vixen, and auxiliary telescope components.


While the free version of XEphem only includes a subset of the SKYMAP Master Catalog and the Messier Catalog, the internal format of the remaining catalogs can be inferred from the source code, and e.g. the internal binary Tycho-2 catalog can be generated from the original data.[8] This is also possible for the non-stellar catalogs in the ASCII .edb format, such as for HYPERLEDA.[9]

XEphem can also read several astrometric catalogs in their original formats:

Numerical routines are used in PyEphem with permission of Elwood Downey.[14]

See also[edit]


  1. ^ "XEphem history". Retrieved 2015-09-28.
  2. ^ "Changelog". Retrieved 2017-06-17.
  3. ^ "Free XEphem downloads". Retrieved 29 September 2015.
  4. ^ "Purchase XEphem". Retrieved 29 September 2015.
  5. ^ Chapront, J. (1995). "Representation of planetary ephemerides by frequency analysis. Application to the five outer planets". Astronomy and Astrophysics Supplement Series. 109: 181. Bibcode:1995A&AS..109..181C.
  6. ^ J. Meeus, Astronomical Formulae for Calculators (Willmann-Bell, Richmond, VA, 1982).
  7. ^ Digital Lunar Orbiter Photographic Atlas of the Moon
  8. ^ see e.g. Programs to generate XEphem 3.4 xe2 catalogs
  10. ^ CDS VizieR Guide Star Catalog
  11. ^ CDS VizieR GSC-ACT
  12. ^ USNO PMM catalogs
  13. ^ CDS VizieR UCAC2
  14. ^ "PyEphem Home Page".

External links[edit]