The History of HM Nautical Almanac Office

The Royal Greenwich Observatory was founded in 1675 by decree of Charles II for the sole purpose of improving the level of astronomical knowledge required to support navigation at sea.

The present-day work of HM Nautical Almanac Office continues a 323-year-old tradition, bringing the latest techniques in astronomy and computation to the publication of The Nautical Almanac and all of our other books, software and data services.

1675: The Founding of the Royal Greenwich Observatory

The RGO was founded in 1675 by decree of Charles II. The first Astronomer Royal, John Flamsteed, was charged "to apply himself with the most exact care and diligence to the rectifying of the tables of the motions of the heavens, and the places of the fixed stars, so as to find out the so much desired longitude of places for the perfecting the art of navigation."

1767: The Nautical Almanac

Almost a century was to elapse between the founding of the RGO and the first edition of The Nautical Almanac under the fifth Astronomer Royal, Nevil Maskelyne. This almanac contained tabulations of the distances of the Moon's centre from the Sun and from the bright stars for every three hours, so that the navigator could determine Greenwich time and hence his longitude from observations of such lunar distances.

1832: The Nautical Almanac Office

The Nautical Almanac Office was established as a separate institution in 1832 under the auspices of the Admiralty who took over when the Board of Longitude was abolished. Considerable improvements in the contents and presentation of the Almanac were introduced in 1834 by WS Stratford following a survey of the Astronomical Society who wanted more data for astronomers.

1911: International Cooperation

In 1911, the (then) five principal ephemeris-producing nations (France, Germany, Great Britain, Spain and the United States) agreed to co-operate in the production of almanac data, with the aims of avoiding duplication of effort and of standardising the basis upon which the ephemerides were computed. This cooperation was further strengthened with the creation, in 1919, of the International Astronomical Union.

HMNAO and the Nautical Almanac Office of USNO now collaborate closely in every aspect of the production of The Nautical Almanac, The Astronomical Almanac and the other publications for which the two Offices are responsible. The Almanacs are produced in accordance with resolutions of the International Astronomical Union to meet the needs of astronomers, sailors and aviators worldwide.

1914: The Nautical Almanac, Abridged for the Use of Seamen

It was recognised late in the 19th century that the Nautical Almanac contained much information that was of little relevance to the practical navigator. In 1896, Part I (which contained the navigational data) was published separately for the first time. In 1914, the separation was made formal with the introduction of Nautical Almanac, Abridged for the Use of Seamen which was specially designed for navigation. This almanac underwent further changes in 1929 and 1952, when it was renamed to the Abridged Nautical Almanac, and again in 1958. It regained its original title of Nautical Almanac in 1960.

1937: Re-united with the RGO

In 1937 HMNAO became part of the Royal Greenwich Observatory and the Astronomer Royal was once again responsible for overseeing the work of the Office. However, the Office remained separate from the Observatory until it moved to Herstmonceux in 1949.

1959: Electronic Computing

The computation of the data for the almanacs involved a considerable amount of effort. As late as the mid-20th century, HMNAO employed a small army of human computers to carry out this work. They used the latest technology available at the time: logarithm tables, mechanical calculating machines and electro-mechanical calculating machines. In 1959 the Office obtained its own electronic computer, making it the first part of the RGO to use this emerging technology.

Today, computation of the contents of an edition of The Nautical Almanac is carried out on a Unix workstation, and much of the layout work is carried out using TeX on PCs.

1998: The closure of the RGO

With the closure of the RGO, HM Nautical Almanac Office moved to the Rutherford Appleton Laboratory near Chilton, Didcot in Oxfordshire under the auspices of the Council for the Central Laboratory of the Research Councils under the supervision of P.T. Wallace.

2000: The future of HM Nautical Almanac Office

HM Nautical Almanac Office has always been ready to adopt new technologies, the better to meet the needs of existing customers and to seek out new users for our products. The rapid growth of the Internet and of computers in home, schools and the workplace has spurred us to look at new ways to present our products and services. These web pages are one example; another is forthcoming The Astronomer's Diary, our first almanac on CD-ROM.

You may also like to see the list of Superintendents & Heads and the list of locations which HM Nautical Almanac Office has occupied in its 170-year history.

HM Nautical Almanac Office, Rutherford Appleton Laboratory
Last revision was made on 2001 January 8