![Nautical almanac 01](https://upload.wikimedia.org/wikipedia/commons/f/f9/Nautical_almanac_01.png)
A nautical almanac is a publication describing the positions of a selection of
celestial bodies 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 primar ...
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 of ...
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. Declination's angle is measured north or south of the ...
and
Greenwich
Greenwich ( , ,) is a town in south-east London, England, within the ceremonial county of Greater London. It is situated east-southeast of Charing Cross.
Greenwich is notable for its maritime history and for giving its name to the Greenwich ...
hour angle
In astronomy and celestial navigation, the hour angle is the angle between two planes: one containing Earth's axis and the zenith (the '' meridian plane''), and the other containing Earth's axis and a given point of interest (the ''hour circle ...
) at which the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
,
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
,
planet
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
s, and
First Point of Aries is directly overhead. The positions of 57 selected
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
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 northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It is ...
, ''
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 al ...
'' has been published annually by
HM Nautical Almanac Office
His Majesty's Nautical Almanac Office (HMNAO), now part of the United Kingdom Hydrographic Office, was established in 1832 on the site of the Royal Observatory, Greenwich (ROG), where ''The Nautical Almanac'' had been published since 1767. HMNAO ...
, ever since the first edition was published in 1767.
[
]
[
]
In the United States, a nautical
almanac
An almanac (also spelled ''almanack'' and ''almanach'') is an annual publication listing a set of current information about one or multiple subjects. It includes information like weather forecasts, farmers' planting dates, tide tables, and othe ...
has been published annually by the
US Naval Observatory
United States Naval Observatory (USNO) is a scientific and military facility that produces geopositioning, navigation and timekeeping data for the United States Navy and the United States Department of Defense. Established in 1830 as the Depo ...
since 1852.
It was originally titled ''
American Ephemeris and Nautical Almanac''. 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 2015, (United States Naval Observatory/Nautical Almanac Office, 2014) . is an almanac published by the United States Naval Observatory (USNO) and His Majesty's Nautical Almanac ...
'' for use by the navies of both countries.
Almanac data is now available online from the US Naval Observatory.
[
]
[
]
Also commercial
almanac
An almanac (also spelled ''almanack'' and ''almanach'') is an annual publication listing a set of current information about one or multiple subjects. It includes information like weather forecasts, farmers' planting dates, tide tables, and othe ...
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
Adlard Coles Nautical is a nautical publisher, with over 300 books in print. The company publishes books on topics of interest to sailors and motorboaters and also ‘landlubbers’ with an interest in the sea. Their list includes almanacs, cruis ...
, 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 Tuesday, 6 June 1944 of the Allied invasion of Normandy in Operation Overlord during World War II. Codenamed Operation Neptune and often referred to as ...
.
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 movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
. The
Sokkia
{{Infobox company, name = Sokkia Co., Ltd.
, type = Public K.K.
, foundation = 1920
, location = Atsugi, Kanagawa, Japan
, key_people = Jin Ito
, industry = High precision instruments for construction, ...
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
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 of ...
, 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 celes ...
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), or in the modern ...
. 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.
See also
*
Bowditch's ''American Practical Navigator''
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
{{DEFAULTSORT:Nautical Almanac
Sailing books
Maritime books
*