XEphem

XEphem started as a Unix and Motif conversion of the IBM PC-based {{Proper name|ephem}}. It was initially released in December 1993 with version 2.5.{{Citation needed|reason = this claim seems to be present in a few places on the web, but it seems that the source is wikipedia itself... any other sources?|date=September 2015}} Its commercial edition was discontinued in 2016; the free version continued to be offered as proprietary software.{{cite web|url=https://groups.io/g/xephem/topic/18594626#3539 |title=thanks for using XEphem |last=Downey |first=Elwood |date=2016-10-31 |website=Groups.io |access-date=2021-05-29 |archive-url=https://web.archive.org/web/20210529074530/https://groups.io/g/xephem/topic/18594626#3539 |archive-date=2021-05-29}} In 2021, however, Downey relicensed XEphem's source code under the MIT License, raising the release version from 3.7.7 to 4.0.0 to highlight the change.{{cite web|url=https://groups.io/g/xephem/topic/80461705#3770 |title=XEphem now released under MIT Open Source license |last=Downey |first=Elwood |date=2021-02-07 |website=Groups.io |access-date=2021-05-29 |archive-url=https://web.archive.org/web/20210529075021/https://groups.io/g/xephem/topic/80461705#3770 |archive-date=2021-05-29}}

XEphem uses

• The VSOP87D planetary theory (full and reduced precision) for Solar System ephemeris,
• Approximation to DE200{{Cite journal |bibcode = 1995A&AS..109..181C|title = Representation of planetary ephemerides by frequency analysis. Application to the five outer planets|last1 = Chapront|first1 = J.|journal = Astronomy and Astrophysics Supplement Series|year = 1995|volume = 109|pages = 181}} for the outer planets and Pluto, and
• Formulae from J. Meeus (1982)J. Meeus, Astronomical Formulae for Calculators (Willmann-Bell, Richmond, VA, 1982). for Jovian and Saturnian natural satellites
• Model by the Bureau des Longitudes for Martian and Uranian natural satellites

and includes

• About 452 million stars from both the Tycho-2 Catalogue and a magnitude limited subset of the Guide Star Catalog II,
• About 1 million deep sky objects mainly from a subset of HYPERLEDA,
• About 288,000 minor planets and comets orbital elements from the IAU Minor Planet Center and Lowell Observatory (that can be updated),

and other specialized catalogs. It also include the Digital Lunar Orbiter Photographic Atlas of the Moon.[http://www.lpi.usra.edu/resources/lunar_orbiter/ Digital Lunar Orbiter Photographic Atlas of the Moon] 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.see e.g. [http://hexadecimal.uoregon.edu/xephemcatalogs/ Programs to generate XEphem 3.4 xe2 catalogs] This is also possible for the non-stellar catalogs in the ASCII .edb format, such as for HYPERLEDA.[http://cdsarc.u-strasbg.fr/viz-bin/Cat?VII/237 CDS VizieR HYPERLEDA]

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

• GSC 1.2[http://cdsarc.u-strasbg.fr/viz-bin/Cat?I/254 CDS VizieR Guide Star Catalog] and GSC-ACT[http://cdsarc.u-strasbg.fr/viz-bin/Cat?I/255 CDS VizieR GSC-ACT]
• USNO A/SA 1.0/2.0[ftp://ftp.nofs.navy.mil/pub/ USNO PMM catalogs]{{dead link|date=May 2025|bot=medic}}{{cbignore|bot=medic}}
• UCAC2 [http://cdsarc.u-strasbg.fr/viz-bin/Cat?I/289 CDS VizieR UCAC2]

Numerical routines are used in PyEphem with permission of Elwood Downey.{{cite web

|url=http://rhodesmill.org/pyephem/index.html

|title=PyEphem Home Page}}

{{Portal|Free and open-source software|Astronomy}}

• C2A
• Cartes du Ciel
• Celestia
• Digital Universe Atlas
• Google Mars
• Google Moon
• Google Sky
• Hallo Northern Sky (HN Sky)
• KStars
• NASA World Wind
• RedShift
• Starry Night
• Stellarium
• TheSky
• Universe Sandbox
• WinStars
• WorldWide Telescope

{{Reflist}}

• {{Official website|http://www.clearskyinstitute.com/xephem/}}
• {{Github|XEphem}}
• {{cite web|url=https://build.opensuse.org/search?search_text=xephem|title=openSUSE RPM}} | {{cite web|url=https://pkgs.org/download/xephem|title=Linux RPMs}}
• {{cite web| url=http://hexadecimal.uoregon.edu/xephemcatalogs| title=Programs to generate XEphem 3.4 xe2 catalogs|first1=Steve |last1=VanDevender}}

{{DEFAULTSORT:Xephem}}

Category:Free astronomy software

Category:Planetarium software for Linux

Category:Science software for macOS