The Astronomical Almanac

The Astronomical Almanac, formerly known as The American Ephemeris and Nautical Almanac and The Nautical Almanac and Astronomical Ephemeris, is a publication that provides astronomical data. It contains tables detailing the positions of celestial bodies, which are essential for astronomers and navigators.1

Historically, ephemerides have been calculated based on theories of celestial motion derived from observations. The development of mechanical and electronic calculators has significantly improved the speed and accuracy of these computations.1

Several national ephemerides are published regularly, with the oldest being the Connaissance des temps, founded in Paris in 1679. The Astronomical Almanac is the result of a unification of the British and American national publications, sharing identical content and computational work. This almanac is crucial for celestial navigation, providing coordinates for celestial objects that allow navigators to determine their position using instruments like a sextant.12