A nautical almanac is a publication describing the positions of a selection of

celestial bodies An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists within the observable universe. In astronomy, the terms ''object'' and ''body'' are of ...

for the purpose of enabling

navigator A navigator is the person on board a ship or aircraft responsible for its navigation.Grierson, MikeAviation History—Demise of the Flight Navigator FrancoFlyers.org website, October 14, 2008. Retrieved August 31, 2014. The navigator's prim ...

s to use

celestial navigation Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the surface ...

to determine the position of their ship while at sea. The Almanac specifies for each whole hour of the year the position on the Earth's surface (in

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...

and

Greenwich Greenwich ( , , ) is an List of areas of London, area in south-east London, England, within the Ceremonial counties of England, ceremonial county of Greater London, east-south-east of Charing Cross. Greenwich is notable for its maritime hi ...

hour angle In astronomy and celestial navigation, the hour angle is the dihedral angle between the '' meridian plane'' (containing Earth's axis and the zenith) and the '' hour circle'' (containing Earth's axis and a given point of interest). It may be ...

) at which the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

s, and First Point of Aries is directly overhead. The positions of 57 selected

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

s are specified relative to the First Point of Aries. In

Great Britain Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...

, ''

The Nautical Almanac ''The Nautical Almanac'' has been the familiar name for a series of official British almanacs published under various titles since the first issue of ''The Nautical Almanac and Astronomical Ephemeris'', for 1767: this was the first nautical alm ...

'' has been published annually by HM Nautical Almanac Office, ever since the first edition was published in 1767. In the United States, a nautical

almanac An almanac (also spelled almanack and almanach) is a regularly published listing of a set of current information about one or multiple subjects. It includes information like weather forecasting, weather forecasts, farmers' sowing, planting dates ...

has been published annually by the US Naval Observatory since 1852. It was originally titled ''

American Ephemeris and Nautical Almanac ''The American Ephemeris and Nautical Almanac'' was published for the years 1855 to 1980, containing information necessary for astronomers, surveyors, and navigators. It was based on the original British publication, '' The Nautical Almanac and Ast ...

''. Since 1958, the USNO and HMNAO have jointly published a unified nautical almanac, ''The

Astronomical Almanac The ''Astronomical Almanac''The ''Astronomical Almanac'' for the Year 2024, © Crown Copyright 2023, ISSN 0737-6421 . is an almanac published by the United Kingdom Hydrographic Office; it also includes data supplied by many scientists from around ...

'' for use by the navies of both countries. Almanac data is now available online from the US Naval Observatory. Also commercial

s were produced that combined other information. A good example would be Brown's, which commenced in 1877, and is still produced annually, its early 20th-century subtitle being "Harbour and Dock Guide and Advertiser and Daily Tide Tables". This combination of trade advertising, and information "by permission... of the Hydrographic Department of the Admiralty" provided a useful compendium of information. More recent editions have kept up with the changes in technology: the 1924 edition, for instance, had extensive advertisements for coaling stations. Meanwhile, the Reeds Nautical Almanac, published by Adlard Coles Nautical, has been in print since 1932, and in 1944 was used by landing craft involved in the

Normandy landings The Normandy landings were the landing operations and associated airborne operations on 6 June 1944 of the Allies of World War II, Allied invasion of Normandy in Operation Overlord during the Second World War. Codenamed Operation Neptune and ...

. The "Air Almanac" of the United States and Great Britain tabulates celestial coordinates for 10-minute intervals for use in aerial

navigation Navigation is a field of study that focuses on the process of monitoring and controlling the motion, movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navig ...

. The Sokkia Corporation's annual "Celestial Observation Handbook and Ephemeris" tabulated daily celestial coordinates (to a tenth of an arcsecond) for the Sun and nine stars; it was last published for 2008. To find the position of a ship or aircraft by

, the navigator measures with a

sextant A sextant is a doubly reflecting navigation instrument that measures the angular distance between two visible objects. The primary use of a sextant is to measure the angle between an astronomical object and the horizon for the purposes of cel ...

the apparent height of a celestial body above the horizon, and notes the time from a

marine chronometer A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation. It is used to determine longitude by comparing Greenwich Mean Time (GMT), and the time at t ...

. That height is compared with the height predicted for a trial position; the arcminutes of height difference is how many nautical miles the position line is from the trial position.

References

External links

Nautical Almanac, Board of Longitude Collection
(Cambridge University Library)
Her Majesty's Nautical Almanac OfficeOnline Nautical AlmanacThe free online Nautical Almanac in PDF formatA free Nautical Almanac in PDF formatHistory of the Nautical Almanac

Nautical Almanac - App for android

Nautical Almanac - Free App for Windows
{{DEFAULTSORT:Nautical Almanac Sailing books Maritime books *

See also

References

External links