The Nautical Almanac

Last updated

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: [1] this was the first nautical almanac to contain data dedicated to the convenient determination of longitude at sea. It was originally published from the Royal Greenwich Observatory in England. [2] [3] [4] A detailed account of how the publication was produced in its earliest years has been published by the National Maritime Museum. [5]

Contents

Since 1958 (with the issue for the year 1960), His Majesty's Nautical Almanac Office and the US Naval Observatory have jointly published a unified Nautical Almanac, for use by the navies of both countries. [6]

Publication history

The changing names and contents of related titles in the series are summarised as follows. (The issue years mentioned below are those for which the data in the relevant issue were calculated—and the issues were in practice published in advance of the year for which they were calculated, at different periods of history, anything from 1 to 5 years in advance).

(For many years, official nautical almanacs and astronomical ephemerides in the UK and the USA had a linked history, and they became merged in both titles and contents in 1981.) [4]

In the UK, the official publications have been: [3] [7]

1767–1959

The main distinctive feature of the inaugural issue for 1767 was the tabulation of lunar distances as a tool to facilitate the determination of longitude at sea from observations of the Moon. [8] Within a few years, the publishers of almanacs of other countries began to adopt the practice of tabulating lunar distances. [9] Lunar distances continued to be published in the UK official almanacs until 1906, by which time their use had declined in practice. For some time thereafter, in the issues for the years 1907–1919, examples of how to calculate them were given instead. [10]

Time: The issues for 1767 to 1833 gave their ephemeris tabulations in terms of Greenwich apparent (not mean) time. This was on the grounds that an important class of user was the 'Mariner', and that 'apparent Time' was "the same which he will obtain by the Altitudes of the Sun or Stars in the Manner hereafter prescribed". Mean time at Greenwich (i.e. mean solar time) was adopted as from the issue for 1834 and continued to 1959. [11] Until the issue for 1924, the time argument for Greenwich Mean Time was counted from 0h starting at Greenwich mean noon (on the civil day with the same number), and starting with the issue for 1925 the commencement point of the time argument was changed so that 0h became midnight at the beginning of the civil day with the relevant number, to coincide for the future with the civil reckoning.

During parts of the period 1767–1959, separate subsidiary titles dedicated to navigation were also published:

1960–1980

Time: A major change introduced with the 1960 issue of The Astronomical Ephemeris was the use of ephemeris time in place of mean solar time for the major ephemeris tabulations. [12] But the Nautical Almanac, now continuing as a separate publication addressed largely to navigators, continued to give tabulations based on mean solar time (UT).

1981 to date

The British Nautical Almanac in the United States

In the US, an official (and initially separate) series of ephemeris publications began with the issue for 1855 as The American Ephemeris and Nautical Almanac ; but before that, the British Nautical Almanac was commonly used on American ships and in the United States [13] – sometimes in the form of an independently printed American 'impression' instead. [14]

Modern alternative data sources

Almanac data is now also available online from the US Naval Observatory. [15]

Related Research Articles

<span class="mw-page-title-main">Ecliptic</span> Apparent path of the Sun on the celestial sphere

The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic against the background of stars. The ecliptic is an important reference plane and is the basis of the ecliptic coordinate system.

The term ephemeris time can in principle refer to time in association with any ephemeris. In practice it has been used more specifically to refer to:

  1. a former standard astronomical time scale adopted in 1952 by the IAU, and superseded during the 1970s. This time scale was proposed in 1948, to overcome the disadvantages of irregularly fluctuating mean solar time. The intent was to define a uniform time based on Newtonian theory. Ephemeris time was a first application of the concept of a dynamical time scale, in which the time and time scale are defined implicitly, inferred from the observed position of an astronomical object via the dynamical theory of its motion.
  2. a modern relativistic coordinate time scale, implemented by the JPL ephemeris time argument Teph, in a series of numerically integrated Development Ephemerides. Among them is the DE405 ephemeris in widespread current use. The time scale represented by Teph is closely related to, but distinct from, the TCB time scale currently adopted as a standard by the IAU.
<span class="mw-page-title-main">Greenwich Mean Time</span> Time zone of Western Europe, same as WET

Greenwich Mean Time (GMT) is the mean solar time at the Royal Observatory in Greenwich, London, counted from midnight. At different times in the past, it has been calculated in different ways, including being calculated from noon; as a consequence, it cannot be used to specify a particular time unless a context is given. The term GMT is also used as one of the names for the time zone UTC+00:00 and, in UK law, is the basis for civil time in the United Kingdom.

<span class="mw-page-title-main">Nevil Maskelyne</span> British astronomer and physicist (1732–1811)

Nevil Maskelyne was the fifth British Astronomer Royal. He held the office from 1765 to 1811. He was the first person to scientifically measure the mass of the planet Earth. He created the British Nautical Almanac and Astronomical Ephemeris for the Meridian of the Royal Observatory at Greenwich using Tobias Mayer's corrections for Euler's Lunar Theory tables.

<span class="mw-page-title-main">Charles Mason</span> English astronomer and surveyor (1728–1786)

Charles Mason was an English astronomer who made significant contributions to 18th-century science and American history, particularly through his survey with Jeremiah Dixon of the Mason–Dixon line, which came to mark the border between Maryland and Pennsylvania (1764–1768). The border between Delaware and Maryland is also defined by a part of the Mason–Dixon line.

<span class="mw-page-title-main">Peter Andreas Hansen</span> German astronomer (1795–1874)

Peter Andreas Hansen was a Danish-born German astronomer.

The year 1767 in science and technology involved some significant events.

Newcomb's Tables of the Sun is a work by the American astronomer and mathematician Simon Newcomb, published in volume VI of the serial publication Astronomical Papers Prepared for the Use of the American Ephemeris and Nautical Almanac. The work contains Newcomb's mathematical development of the position of the Earth in the Solar System, which is constructed from classical celestial mechanics as well as centuries of astronomical measurements. The bulk of the work, however, is a collection of tabulated precomputed values that provide the position of the sun at any point in time.

<span class="mw-page-title-main">Nautical almanac</span>

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 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.

Lunar theory attempts to account for the motions of the Moon. There are many small variations in the Moon's motion, and many attempts have been made to account for them. After centuries of being problematic, lunar motion can now be modeled to a very high degree of accuracy.

<span class="mw-page-title-main">Longitude by chronometer</span>

Longitude by chronometer is a method, in navigation, of determining longitude using a marine chronometer, which was developed by John Harrison during the first half of the eighteenth century. It is an astronomical method of calculating the longitude at which a position line, drawn from a sight by sextant of any celestial body, crosses the observer's assumed latitude. In order to calculate the position line, the time of the sight must be known so that the celestial position i.e. the Greenwich Hour Angle and Declination, of the observed celestial body is known. All that can be derived from a single sight is a single position line, which can be achieved at any time during daylight when both the sea horizon and the sun are visible. To achieve a fix, more than one celestial body and the sea horizon must be visible. This is usually only possible at dawn and dusk.

<span class="mw-page-title-main">Lunar distance (navigation)</span> Angular distance between the Moon and another celestial body

In celestial navigation, lunar distance, also called a lunar, is the angular distance between the Moon and another celestial body. The lunar distances method uses this angle and a nautical almanac to calculate Greenwich time if so desired, or by extension any other time. That calculated time can be used in solving a spherical triangle. The theory was first published by Johannes Werner in 1524, before the necessary almanacs had been published. A fuller method was published in 1763 and used until about 1850 when it was superseded by the marine chronometer. A similar method uses the positions of the Galilean moons of Jupiter.

Richard Dunthorne was an English astronomer and surveyor, who worked in Cambridge as astronomical and scientific assistant to Roger Long, and also concurrently for many years as surveyor to the Bedford Level Corporation.

The Astronomical Almanac is an almanac published by the United States Naval Observatory (USNO) and His Majesty's Nautical Almanac Office (HMNAO); it also includes data supplied by many scientists from around the world. It is considered a worldwide resource for fundamental astronomical data, often being the first publication to incorporate new International Astronomical Union resolutions. The almanac largely contains Solar System ephemeris and catalogs of selected stellar and extragalactic objects. The material appears in sections, each section addressing a specific astronomical category. The book also includes references to the material, explanations, and examples. It is available one year in advance of its date.

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 Astronomical Ephemeris, with which it merged to form The Astronomical Almanac, published from the year 1981 to the present.

<span class="mw-page-title-main">History of longitude</span> Record of humanitys attempts to find east-west position on Earth

The history of longitude describes the centuries-long effort by astronomers, cartographers and navigators to discover a means of determining the longitude of any given place on Earth. The measurement of longitude is important to both cartography and navigation. In particular, for safe ocean navigation, knowledge of both latitude and longitude is required, however latitude can be determined with good accuracy with local astronomical observations.

A fundamental ephemeris of the Solar System is a model of the objects of the system in space, with all of their positions and motions accurately represented. It is intended to be a high-precision primary reference for prediction and observation of those positions and motions, and which provides a basis for further refinement of the model. It is generally not intended to cover the entire life of the Solar System; usually a short-duration time span, perhaps a few centuries, is represented to high accuracy. Some long ephemerides cover several millennia to medium accuracy.

Mary Edwards was a human computer for the British Nautical Almanac and one of a very few women paid directly by the Board of Longitude, and to earn a living from scientific work at the time.

Raphael's Ephemeris is an ephemeris, or set of tables, used in astrology to determine the position of the Sun, Moon and planets. Raphael was a pseudonym used by the original author of the ephemeris, Robert Cross Smith.

<span class="mw-page-title-main">John Crosley</span> English astronomer and mathematician

John Crosley (1762–1817) was an English astronomer and mathematician who was an assistant at the Royal Observatory, Greenwich, a computer of the Nautical Almanac, an observer on maritime voyages of scientific exploration and a member and President of the Spitalfields Mathematical Society.

References

  1. ↑ Nevil Maskelyne, The Nautical Almanac and Astronomical Ephemeris, for the year 1767 (London: J. Nourse & Mess. Mount and Page, 1766).
  2. ↑ "The History of HM Nautical Almanac Office". HM Nautical Almanac Office. Archived from the original on 30 June 2007. Retrieved 31 July 2007.
  3. 1 2 'ESAE 1961': Explanatory Supplement to the Astronomical Ephemeris and the American Ephemeris and Nautical Almanac ('prepared jointly by the Nautical Almanac Offices of the United Kingdom and the United States of America', HMSO, London, 1961)
  4. 1 2 3 'ESAA 1992': ed. P.K. Seidelmann, Explanatory Supplement to the Astronomical Almanac (CA, 1992).
  5. ↑ Croarken (2002), pp. 106–126.
  6. ↑ "History of the Nautical Almanac". US Naval Observatory. Archived from the original on 20 August 2018. Retrieved 11 October 2010.
  7. ↑ ESAE 1961, see esp. sect. 1B.
  8. ↑ D. Howse, Nevil Maskelyne – The Seaman's Astronomer, Cambridge, 1989, esp. at p. 87; also, on p. 90, Howse points out that the idea of an almanac with lunar distances had previously been proposed in France, by De Lalande in the French almanac Connoissance des temps pour l'année 1761 au méridien de Paris (published 1759), based on Lacaille's work on lunar distance. He had provided a sample table of pre-computed lunar distances for fourteen days of July 1761, tabulated at 4-hour intervals, and promised more to come, but the proposal was not further implemented there.
  9. ↑ Guy Boistel, L'astronomie nautique au XVIIIe siècle en France: tables de la Lune et longitudes en mer (2001), vol. 1, p. 264, showing for example that Lalande in Paris incorporated lunar distances into the long-established 'Connaissance des Temps' as from the issue for 1774 (published 1772) – initially as a copy of the English lunar-distance data, and still based on the Greenwich meridian as in the Nautical Almanac itself, moving later to lunar-distance data independently calculated for the meridian of Paris.
  10. ↑ ESAE 1961, sect. 7D, p. 190.
  11. ↑ ESAE 1961, at pp. 3–5, sect. 1B.
  12. ↑ ESAA 1992, p. 612.
  13. ↑ ESAE 1961, sect. 1B
  14. ↑ G.W. Blunt White Library at the Mystic Seaport Museum, Mystic, Connecticut, CT 06355, USA, for a copy of an independent 'Second American impression' of (the British title) The Nautical Almanac and Astronomical Ephemeris for 1804, e.g. at https://library.mysticseaport.org/initiative/ImPage.cfm?PageNum=1&BibId=21382&ChapterId=1%5B%5D (retrieved Feb 19, 2009)
  15. ↑ "Data Services". US Naval Observatory. Retrieved 27 July 2022.

Bibliography

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.