Nautical almanac

Nautical almanac
Two sample pages of the 2002 Nautical Almanac published by the U.S. Naval Observatory

A nautical almanac is a publication describing the positions of a selection of celestial bodies for the purpose of enabling navigators to use celestial navigation 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 and Greenwich hour angle) at which the sun, moon, planets and first point of Aries is directly overhead. The positions of 57 selected stars are specified relative to the first point of Aries.

In Great Britain, The Nautical Almanac has been published annually by HM Nautical Almanac Office, ever since the first edition was published in 1767. [1] [2] In the United States of America, a nautical almanac has been published annually by the US Naval Observatory since 1852.[2] Since 1958, the USNO and HMNAO have jointly published a unified nautical almanac, for use by the navies of both countries.[2] Almanac data is now available online from the US Naval Observatory.[3] [4]

Also commercial almanacs were produced that combined other information. A good example would be Brown's — which commenced in 1877 - and is still produced annually, its early twentieth 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.

The "Air Almanac" of the United States and Great Britain tabulates celestial coordinates for 10 minute intervals for the use in aerial navigation. 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 publishd for 2008.

To find the position of a ship or aircraft by celestial navigation, the navigator measures with a sextant the apparent height of a celestial body above the horizon, and notes the time from a marine chronometer. That height is compared with the height predicted for a trial position; the arcminutes of height difference is how many nautical miles the the position line is from the trial position.

See also

Yacht foresail.svg Nautical portal


External links

Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Nautical almanac — Nautical Nau tic*al, a. [L. nauticus, Gr. naytiko s, fr. nay ths a seaman, sailor, fr. nay^s ship: cf. F. nautique. See {Nave} of a church.] Of or pertaining to seamen, to the art of navigation, or to ships; as, nautical skill. [1913 Webster] Syn …   The Collaborative International Dictionary of English

  • Nautical almanac — Almanac Al ma*nac (?; 277), n. [LL. almanac, almanach: cf. F. almanach, Sp. almanaque, It. almanacco, all of uncertain origin.] A book or table, containing a calendar of days, and months, to which astronomical data and various statistics are… …   The Collaborative International Dictionary of English

  • Nautical Almanac — (engl., spr. nahtĭkĕl ahlmĕnäck), s. Nautisches Jahrbuch; Nautical mile (spr. meil), Seemeile …   Kleines Konversations-Lexikon

  • Nautical Almanac — noun A periodical book of astronomical tables specially useful to sailors • • • Main Entry: ↑nautical …   Useful english dictionary

  • Nautical Almanac — Nautical Almanac, s. Ephemeriden …   Meyers Großes Konversations-Lexikon

  • Nautical Almanac — Der Nautical Almanac (Nautical almanac and astronomical ephemeris) ist ein astronomisches Jahrbuch von etwa 300 Seiten, das speziell für die rasche Astronavigation auf See geschaffen wurde. Der erste Almanach des britischen Royal Greenwich… …   Deutsch Wikipedia

  • Nautical Almanac (band) — Nautical Almanac are a noise music group based out of Baltimore Maryland with a rotating membership based around Carly Ptak and Twig Harper.[citation needed] Contents 1 History 2 Select discography 2.1 …   Wikipedia

  • Nautical almanac (disambiguation) — Nautical Almanac can refer to: Nautical almanac a publication describing the positions and movements of celestial bodies American Ephemeris and Nautical Almanac first published in 1852 U.S. Nautical Almanac, part of the American Ephemeris and… …   Wikipedia

  • Nautical Almanac Office — can refer to: HM Nautical Almanac Office in the United Kingdom The Nautical Almanac Office at the United States Naval Observatory This disambiguation page lists articles associated with the same title. If an …   Wikipedia

  • nautical almanac — yearly journal containing information needed by sailors (such as tides, moon phases, sunrise, etc.) …   English contemporary dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”