The Nautical Almanac & Its Superintendents
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1960: The Nautical Almanac

 

After the war Sadler, and his opposite number at the United States Naval Observatory (USNO), G. M. Clemence, worked toward "joint" publications between the two Almanac Offices. This met with the full approval of the British Admiralty and the American Navy Department for the complete unification of the (British) Nautical Almanac (the volume for astronomers) and the American Ephemeris under the title [in Britain], from 1960, of The Astronomical Ephemeris.

Similar unification had already been achieved in the case of the Nautical Almanac (formerly theAbridged Nautical Almanac - for seamen) in 1958, and the Air Almanac. All three of these publications were calculated jointly and produced by ordinary processes in one of the two countries and by photolithography from special "reproduction pulls" in theother.

This process of unification involved changes in the publications. For The Nautical Almanac 1952, a complete change was made: the major quantities now tabulated being the Greenwich Hour Angle and Declination of the Sun, Moon and three of the four major planets, together with provision for obtaining the same quantities for about 50 of the brighter stars. According to Wilkins [11] it was Clemence who proposed using a layout of three days at each opening. The final step in the unification of the British and American almanacs took place in 1958.

Cover of US Nautical Almanac 2017
US Nautical Almanac 2017

© USNO

Cover of The Nautical Almanac 2017 (UKHO)
The Nautical Almanac 2017

© UKHO

Today, although the covers are different, the contents are identical and printed from identical Adobe Portable Document Files. The eclipse maps are generated by the Nautical Almanac Office (Astronomical Applications Department) at the USNO. USNO also produced the Concise Sight Reduction Tables (static), which were included in the late 1980s.

As a standard, changes are made in the NA with care for the benefit of the navigator. The changes have included:

1980s:
The position (GHA, Dec) of Venus is for its centre of light rather than the centre of the disc.
1980s:
Sight reduction procedures (using a calculator) with an iterative least-squares algorithm for determining position from sextant observations was added.
1980s:
Concise Sight Reduction tables were added.
1990s:
The percentage of the Moon illuminated included.
1990s:
The equation of time is shaded when it is negative.
2016:
A section on polar phenomena (rise/set etc) for the Sun and Moon at northerly latitudes was added.

Naturally, ephemerides, star catalogues and underlying transformations have been updated and modernised. Otherwise as since 1958, the data for the whole volume, except the eclipse maps, are produced in the United Kingdom.

 

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