Celestial Navigation Publications
Nautical Almanacs, volumes of information that tabulate the position of
various celestial bodies, the times of sunrise and sunset, moonrise and
moonset, and other astronomical data used by navigators, are prepared
jointly by the U.S. Naval Observatory and the Royal Greenwich
Observatory in England. However, the almanac volumes are printed both
in the United States and in England.
The Nautical Almanac is published annually, and the Air Almanac is
published twice each year. These publications give ephemeristic data for
marine and air navigation respectively (the Air Almanac can be, and
sometimes is, used by marine surface navigators). These volumes are
used in many others countries with minor modifications, chiefly changes
in the language used for page headings and in the explanatory material.
The Almanac for Computers is also published by the U.S. Naval
Observatory with mathematical data and instructions for the computation
of ephemeristic data using electronic computers or advanced models of
calculators. These almanacs are discussed in greater detail in later text.
Sight Reduction Tables for Marine Navigation, Pub. No. 229, published by
DMAHTC, in six volumes, each volume covering 16° of latitude, North or
South (1° overlap between volumes) (see chapter 9).
Sight Reduction Tables for Air Navigation, Pub. No. 249, published by
DMAHTC in three volumes; offers somewhat greater ease and speed in
sight reduction, but has a limited range of declination and gives a lower
order of precision as to position (see chapter 9).