History of The Air Almanac
Astronomical Applications Dept. Astronomical Applications Dept.
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Picture of the 2013 Air Almanac box and CD Celestial navigation, used for millennia for sailing the seas, became essential in the 1930's for long aircraft flights, especially over the oceans. The usual techniques for marine celestial navigation required too much time to produce a celestial fix while in flight. Driven to produce an almanac designed to meet the needs of pilots, the various almanac offices around the world developed new and faster procedures.

In the United States interest began in the late 1920s for producing a volume tailored to the needs of aircraft navigators. This interest resulted in the production of the Aeronautical Supplement for September, 1929 to December, 1930; the Supplement for 1931; the revised Nautical Almanac for 1932; The Air Almanac for 1933; and the revised Nautical Almanac for 1934 and 1936. But despite the publication of German (1935), French (1936) and British (1937) Air Almanacs, the Americans did not produce a regular annual volume during the 1930s.

In 1940 as part of the American efforts in World War II, the Nautical Almanac Office received permission to increase its staff to produce an air almanac especially designed for the US air fleet. The office delivered the new Air Almanac in 1941, and it has been published regularly ever since. This new book presented the data as a single sheet per day, with much of the data given in 10 minute intervals appropriate for pilots. One sheet per day was a great convenience for pilots because single pages could be removed and taken on flights. Each page contained the GHA for Aries, Sun, Moon, and those planets suitable for navigation for that day, listed in 10 minute intervals for that day. The new Air Almanac was enthusiastically received. In 1946 George Mixter wrote in the journal Navigation, (volume 1, number 3):

"The American Air Almanac, a child of necessity is the best-constructed almanac yet devised for the use of navigators, and marks the most important step in the simplification of the art of navigation since the work of Marq-Saint-Hilaire."

Other special items added were the sky diagrams, star finder charts for periscopic sextants, Moon visibility charts for high latitudes, and a list of time zones used by various countries.

Initially The Air Almanac was printed in three volumes per year, each covering a four-month period. Beginning with the 1977 edition, two volumes per year were printed each with data for six months. This was reduced to one yearly volume for the 1987 edition. Starting with the 2008 volume, The Air Almanac is now produced solely on CD-ROM.

1941 The edition for 1941 was the first regularly recurring edition produced by the US Nautical Almanac Office. Each year was separated into three volume containing data for four months. It was comb bound, the color of the spine either red, white, or blue depending on the months covered.
1953 Unification of the British and American Air Almanacs. Notation changed from Greenwich Civil Time (GCT) to Greenwich Mean Time (GMT).
1963 The sky diagrams were extended to include the daylight hours (published as a supplement for 1963 and 1964).
1965 Precision of the coordinates of the Sun increased to one-tenth of a minute of arc. Reproductions of the unified volume is used by several foreign countries.
1969 Beginning with the edition for 1969, the daily pages were produced by the Linofilm automatic photocomposing process. Also beginning with this edition, a duplicate set of the daily pages were furnished to France.
1970 Beginning with the edition for 1970, star recognition diagrams for periscopic sextants were included in lieu of astrograph settings.
1973 Beginning with the edition for 1973, day of the year was introduced in the headings. The mean hourly rates of the GHA and declination fo the Sun, Moon, and planets are given on the daily pages.
1977 Beginning with the edition for 1977, two volumes per year were printed each with data for six months. Spines were comb; red for the first six months of the year, blue for the second six months.
1987 Beginning with the edition for 1987, the Air Almanac is printed annually in one volume. The spine is blue.
1999 Beginning with the edition for 1999, the comb binding is replaced with perfect binding.
2006 Beginning with the edition for 2006, a CD-ROM is included that contains all the page images in PDF format.
2008 Beginning with the edition for 2008, the paper publication is no longer produced. The Air Almanac is available on CD-ROM, using a web browser interface to navigate through the publication. This makes it the first USNO navigational almanac to be available only via digital media.
2009 Beginning with the edition for 2009, JPL's DE405/LE403 planetary ephemerides is used, replacing DE200.
2015 Beginning with the edition for 2015, JPL's DE430/LE430 planetary ephemerides is used, replacing DE405/LE405. Entire almanac is freely available via download at USNO's and GPO's websites.