Astronomical and Navigational Almanacs

Scientific research, timekeeping, calendars, and navigation have all depended upon the practical skills of positional astronomy for thousands of years. Today, in the United States, the U.S. Naval Observatory produces the data for celestial navigation and positional astronomy on behalf of the nation.

As part of this responsibility, and in a long-standing collaboration with His Majesty's Nautical Almanac Office in the United Kingdom, the Nautical Almanac Office at the U.S. Naval Observatory produces several annual almanacs. Each edition contains data for one year and is published six months or more in advance of the edition year. His Majesty's Nautical Almanac Office maintains the copyright on the material it contributes.

• The Astronomical Almanac contains precise positions (ephemerides) of most solar system objects, data for eclipses and other astronomical phenomena, and catalogs of selected celestial objects.
• The Astronomical Almanac Online contains complementary information to the printed Astronomical Almanac.
• The Nautical Almanac contains the astronomical data required for sea celestial navigation.
• The Air Almanac contains the astronomical data required for air celestial navigation. Starting with the 2015 edition, users may download the entire almanac free of charge.
• Astronomical Phenomena contains selected data of general interest from The Astronomical Almanac. It is available two years in advance.
• The Explanatory Supplement to the Astronomical Almanac is a detailed reference volume to The Astronomical Almanac. The last edition was in 2013. The Explanatory Supplement is available from University Science Books .
• Ordering Information contains instructions on how to order the above publications.