History of The 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, independent 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 separately 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 His 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.
1855	First edition of The American Ephemeris and Nautical Almanac. Originally available in 1852, with data for 1855. The U.S. book publishes the data using two prime meridians: one in Washington DC and one in Greenwich.
1858	First edition of The American Nautical Almanac. This is a more concise book for navigators, reprinted from portions of The American Ephemeris and Nautical Almanac.
1901	The UK book adopts the U.S. 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 is completely redesigned for navigators and is no longer a reprint of portions of The American Ephemeris and Nautical Almanac. It includes data from France, Germany, Spain and Great Britain.
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. Civil time is introduced with the notation GCT (Greenwich Civil Time).
1934	U.S. book provides the Greenwich hour angle for Sun, Moon, and planets, and the sidereal hour angle for the navigation stars.
1950	Complete redesign of the almanac. Right ascensions discontinued.
1952	Washington ephemerides removed from U.S. book.
1953	Use of GCT, first introduced in the 1925 almanac, is discontinued. It is replaced with Greenwich Mean Time (GMT).
1958	First year of the unified Nautical Almanac for use by the United States Navy and the British Royal Navy. The name American Nautical Almanac kept until the 1960 edition.
1960	Both U.S. and British printings titled The Nautical Almanac.
1971	The arguments of the dip table are given in both meters and feet.
1980s	UTC replaces GMT in Nautical and Air Almanacs.
1984	The Jet Propulsion Laboratory's (JPL) DE200/LE200 lunar and planetary ephemerides adopted as basis.
1989	Concise Sight Reduction Tables and Instructions for sight reduction by computer were introduced, making the Nautical Almanac a self-contained edition for navigators.
2003	JPL's DE405/LE405 lunar and planetary ephemerides adopted as basis.
2006	Incorporated Hipparcos astrometry for stars, and improved precession and nutation algorithms, consistent with International Astronomical Union (IAU) resolutions.
2014	More effective and deeper star finding charts included.
2015	JPL's DE430 lunar and planetary ephemerides adopted as basis.
2016	A new Polar Phenomena section included.