The Explanatory Supplement to the Astronomical Almanac

The book is a detailed reference text to the algorithms and theories used to produce The Astronomical Almanac and covers the history, significance, sources, methods of computation, and use of the data presented in The Astronomical Almanac. Although some material is at an elementary level, the book is not intended as a basic textbook on fundamental positional astronomy. It serves as a valuable reference text to the The Astronomical Almanac for scientists who need further details.

The first edition of the book appeared in 1961. At that time there were two separate publications of the almanac, so the title included both names in full: Explanatory Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac. It was prepared jointly by Her Majesty's Nautical Almanac Office (HMNAO) and the U.S. Nautical Almanac Office and published by Her Majesty's Stationery Office. It was reprinted with amendments in 1972, 1974, and 1977. It was then allowed to go out of print because the International Astronomical Union (IAU) introduced such substantive changes to the underlying algorithms and theory that a major revision to the Explanatory Supplement was needed.

The second (and current) edition of the book appeared in 1992 with the title Explanatory Supplement to the Astronomical Almanac, edited by Dr. P. K. Seidelmann. University Science Books publishes the book. It contains contributions from the U.S. Nautical Almanac Office, Her Majesty's Nautical Almanac Office, the Jet Propulsion Laboratory, Bureau des Longitudes, and Time Service and Astrometry at the U. S. Naval Observatory (USNO).

There have been changes in the computational methods of The Astronomical Almanac since the second edition, including a series of resolutions passed by the IAU. Astronomers from around the world are assisting the almanac offices at USNO and HMNAO to prepare the next revision of the book.

The Explanatory Supplement is available from University Science Books.