Specific chapters on orbital ephemerides, precession, nutation, and Earth rotation. The Explanatory Supplement to the Astronomical Almanac
| Edition | Year | Editors / Contributors | Notes | |---------|------|------------------------|-------| | 1st | 1961 | U.S. Nautical Almanac Office (USNO) & H.M. Nautical Almanac Office (HMNAO) | Long out of print; concepts partially superseded. | | 2nd | 1992 | P. Kenneth Seidelmann (ed.) | Major update, now historical but still widely referenced. | | 3rd | 2012 | Sean Urban & P. Kenneth Seidelmann (eds.) | Most current; includes modern IAU resolutions, ICRS, relativistic models. | Nautical Almanac Office (HMNAO) | Long out of
Explanatory Supplement to the Astronomical Almanac is a professional reference manual detailing the theories and algorithms used for astronomical calculations, with the current 3rd edition (2013) covering modern positional astronomy and ICRS reference systems. While official free PDFs of the latest edition are not available, older editions can be accessed through the Internet Archive, with the current version available for purchase or rental via official sources. For more information on the publication, visit U.S. Naval Observatory (USNO) Harvard University | | 3rd | 2012 | Sean Urban & P