History of The Nautical Almanac
Astronomical Applications Dept. Astronomical Applications Dept.
 
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Picture of the 2013 Nautical Almanac The familiar orange book, The Nautical Almanac, along with the chronometer, the sextant, a steady hand and a keen eye, are the resources needed to navigate by the stars. Even today celestial navigation remains a critical backup to GPS and other electronic navigation systems.

The British first published the Nautical Almanac and Astronomical Ephemeris in 1766, with data for 1767. In the United States, the naval appropriations act of 3 March 1849 authorized the preparation and publication of the data necessary for navigation. For this purpose the U.S. Nautical Almanac Office was established in the same year. The American Ephemeris and Nautical Almanac was first published in 1852, with data for 1855. The Nautical Almanac has been published separate from its parent publication in the UK since 1914, and in the U.S. since 1916. Since the unification of the Almanacs in 1958 the U.S. Nautical Almanac Office has produced The Nautical Almanac in full collaboration with Her Majesty's Nautical Almanac Office.

Initially the almanacs provided the data required for the method of lunar distances, a technically demanding and mathematically complex method of determining longitude before the invention of accurate clocks for shipboard use. The common availability of precise chronometers on ships beginning in the early 1800s, and the development of methods of "sight reduction" by Sumner, St.-Hilaire and others, provided an easier procedure for navigators to determine their position at sea. The almanacs provided the necessary data for these methods.

Chronology:
1766 First edition of The Nautical Almanac and Astronomical Ephemeris appears, published by Astronomer Royal of England, with data for 1767. The book provided the information necessary for the method of lunar distances used to determine longitude.
1832 British Nautical Almanac Office is organized
1834 Greenwich Mean Time appears in the book.
1849 U.S. Nautical Almanac Office forms
1852 First edition of The American Ephemeris and Nautical Almanac appears, with data for 1855. The U.S. book publishes the data using two prime meridians: one in Washington DC and one in Greenwich.
1901 The UK book adopts the astronomer Simon Newcomb's tables and constants;
the U.S. follows suit a few years later.
1912 U.S. book removes data for the method of lunar distances
1912 U.S. Congress authorizes international exchange of data.
1914 The UK extracts the sections specific to marine navigation from the UK Nautical Almanac and Astronomical Ephemeris and publishes them separately as the UK Nautical Almanac, Abridged for the Use of Seamen.
1916 The U.S. book includes data from France, Germany, Spain and Britain
1916 The U.S. extracts the sections specific to marine navigation from The American Ephemeris and Nautical Almanac and publishes them separately as the U.S. Nautical Almanac
1919 Sun/Moon rise and set times first appear
1925 Astronomers agree to start the astronomical day at midnight to coincide with the beginning of the civil day.
1934 U.S. book provides the Greenwich Hour Angle for Sun, Moon, and planets and the Sidereal Hour Angle for the navigation stars.
1952 Washington ephemerides removed from U.S. book.
1953 Use of Greenwich Civil Time discontinued
1958 First year of the unified Nautical Almanac for use by the United States Navy and the Royal Navy.
1980s UT replaces GMT in Nautical and Air Almanacs
1984 DE200/LE200 JPL planetary ephemerides adopted as basis
1989 Concise Sight Reduction Tables added
2003 DE405/LE405 JPL planetary ephemerides adopted as basis