Ephemeris
Cross-traditionAstronomical factEditorial synthesis
Definition
A computed table or model giving the positions of the Sun, Moon and planets over time. It is where a chart's numbers actually come from, and naming which one was used is what makes a chart reproducible.
Also called: Ephemerides · Planetary ephemeris
In more depth
Historically an ephemeris was a printed table of daily planetary positions. A modern one is a numerically integrated solution fitted to decades of observational data and distributed as a data file that software reads. The JPL Development Ephemeris series (DE440 and its companions) is one such published solution, described in the peer-reviewed literature.[1]
Which ephemeris was used is part of a chart's provenance, in the same way an edition is part of a citation. Two charts that disagree slightly usually disagree because they were built from different ephemerides, different time scales or different conventions, not because one of them is wrong in an interesting way.[2]
References
Numbered citations in the text link to the records below; each record links to the full source registry.
- Ryan S. Park; William M. Folkner; James G. Williams; Dale H. Boggs. The JPL Planetary and Lunar Ephemerides DE440 and DE441. The Astronomical Journal 161 (3), article 105. 2021. Astronomical fact View source record
- Sean E. Urban (editor); P. Kenneth Seidelmann (editor). Explanatory Supplement to the Astronomical Almanac. Sean E. Urban and P. Kenneth Seidelmann. University Science Books. 2013. Astronomical fact View source record