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TheAstronomical Almanac^[1] is analmanac published by theUnited Kingdom Hydrographic Office; it also includes data supplied by many scientists from around the world. On page vii, the listed major contributors to its various Sections are:H.M Nautical Almanac Office, United Kingdom Hydrographic Office; the Nautical Almanac Office,United States Naval Observatory; theJet Propulsion Laboratory,California Institute of Technology; the IAU Standards Of Fundamental Astronomy (SOFA) initiative; the Institut de Mécanique Céleste et des Calcul des Éphémerides,Paris Observatory; and theMinor Planet Center, Cambridge, Massachusetts.

It is considered a worldwide resource for fundamental astronomical data, often being the first publication to incorporate newInternational Astronomical Union resolutions. The almanac largely containsSolar Systemephemerides based on the JPL Solar System integration "DE440" (created June 2020), andcatalogs of selected stellar and extragalactic objects. The material appears in sections, each section addressing a specific astronomical category. The book also includes references to the material, explanations, and examples. It used to be available up to one year in advance of its date, however the current 2024 edition became available only one month in advance; in December 2023.

TheAstronomical Almanac Online was a companion to the printed volume. It was designed to broaden the scope of the publication, not duplicate the data. In addition to ancillary information, theAstronomical Almanac Online extended the printed version by providing data best presented in machine-readable form.The 2024 printed edition of the Almanac states on page iv: "The web companion toThe Astronomical Almanac has been withdrawn as of January 2023."

Section A

PHENOMENA: includes information on the seasons, phases of the Moon, configurations of the planets, eclipses, transits of Mercury or Venus, sunrise/set, moonrise/set times, and times for twilight. Preprints of many of these data appear inAstronomical Phenomena,^[2] another joint publication by USNO and HMNAO.

Section B

TIME-SCALES AND COORDINATE SYSTEMS: contains calendar information, relationships between time scales, universal and sidereal times, Earth rotation angle, definitions of the various celestial coordinate systems, frame bias, precession, nutation, obliquity, intermediate system, the position and velocity of the Earth, and coordinates of Polaris. Preprints of many of these data also appear inAstronomical Phenomena.^[2]

Section C

SUN; covers detailed positional information on the Sun, including the ecliptic and equatorial coordinates, physical ephemerides, geocentric rectangular coordinates, times of transit, and theequation of time.

Section D

MOON: contains detailed positional information on the Moon including phases, mean elements of the orbit and rotation, lengths of mean months, ecliptic and equatorial coordinates, librations, and physical ephemerides.

Section E

PLANETS: consist of detailed positional information on each of the major planets including osculating orbital elements, heliocentric ecliptic and geocentric equatorial coordinates, and physical ephemerides.

Section F

NATURAL SATELLITES; covers positional information on the satellites of Mars, Jupiter, Saturn (including the rings), Uranus, Neptune, and Pluto.

Section G

DWARF PLANETS AND SMALL SOLAR SYSTEM BODIES: includes positional and physical data on selected dwarf planets, positional information on bright minor planets and periodic comets.

Section H

STARS AND STELLAR SYSTEMS: Beginning with the almanac for the year 2025, the data has been reduced from earlier years to navigational stars, Spectrophotometric standard stars, and ICRF3 radio source positions. Readers are referred tohttps://aa.usno.navy.mil/publications/asa for other data.^[3]

Section J

LUNARCENTRIC CELESTIAL OBJECTS: Beginning in the almanac for the year 2025, tables of celestial objects as observed from the lunar south pole replace the list of observatories that was in earlier editions.^[3]

Section K

TABLES AND DATA: includes Julian dates, selected astronomical constants, relations between time scales, coordinates of the celestial pole, reduction of terrestrial coordinates, interpolations methods, vectors and matrices.

Section L

NOTES AND REFERENCES: gives notes on the data and references for source material found in the almanac.

Section M

GLOSSARY: contains terms and definitions for many of the words and phrases, with emphasis on positional astronomy.

TheAstronomical Almanac is the direct descendant of the British and Americannavigational almanacs. The BritishNautical Almanac and Astronomical Ephemeris had been published since 1766, and was renamedThe Astronomical Ephemeris in 1960.The American Ephemeris and Nautical Almanac had been published since 1852. In 1981 the British and American publications were combined under the titleThe Astronomical Almanac."^[4]

TheExplanatory Supplement to the Astronomical Almanac, currently in its third edition (2013), provides detailed discussion of usage and data reduction methods used by theAstronomical Almanac.^[5] It covers its history, significance, sources, methods of computation, and use of the data. Because theAstronomical Almanac prints primarily positional data, this book goes into great detail on techniques to get astronomical positions. Earlier editions of the supplement were published in 1961^[6] and in 1992.^[7]

• American Ephemeris and Nautical Almanac (specific title)
• Astronomical Ephemeris (generic article)
• Nautical almanac (generic article)
• The Nautical Almanac (familiar name for a specific series of (official British) publications which appeared under a variety of different full titles for the period 1767 to 1959, as well as being a specific official title (jointly UK/US-published) for 1960 onwards)
• Jet Propulsion Laboratory Development Ephemeris (used by theAstronomical Almanac)

• The Astronomical Almanac (official publication at U.S. Naval Observatory website)
• The Astronomical Almanac Online (official publication online at Her Majesty's Nautical Almanac Office website)Archived 2022-11-11 at theWayback Machine

• United States Naval Observatory
• Astronomical almanacs
• Astronomical catalogues

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