The Astronomical Almanac
The Astronomical Almanac
contains a wide variety of both technical and general astronomical
information. The book is a worldwide resource for fundamental astronomical
data. It is a joint publication of the U.S. Nautical Almanac Office and Her
Majesty's Nautical Almanac Office in the United Kingdom, and contains data
supplied by many scientists from around the world. The online companion,
The Astronomical Almanac Online, extends the printed version by
providing data best presented in machine-readable form.
The material appears in sections, each section addressing
a specific astronomical category. The book also includes references to the
material, explanations, and examples. It is available one year in advance
of its date. Parts of Sections A and B are available two years in advance
in Astronomical Phenomena.
- Section A: PHENOMENA
Seasons; Moon's phases; principal occultations; planetary phenomena;
elongations and magnitudes of planets; visibility of planets; diary of
phenomena; times of sunrise, sunset, twilight, moonrise and moonset;
eclipses, transits, use of Besselian elements. Preprints of many of
these data appear in Astronomical Phenomena.
- Section B: TIME-SCALES AND COORDINATE SYSTEMS
Calendar; chronological cycles and eras; religious calendars; relationships
between time scales; universal and sidereal times, Earth rotation angle;
reduction of celestial coordinates; proper motion, annual parallax,
aberration, light-deflection, precession and nutation; coordinates of the
CIP & CIO, matrix elements for both frame bias, precession-nutation, and
ICRS to CIRS; the Celestial Intermediate Reference System, rigorous
formulae for apparent and intermediate place reduction, approximate
formulae for intermediate place reduction; position and velocity of the
Earth; polar motion; diurnal parallax and aberration; altitude, azimuth;
refraction; pole star formulae and table. Preprints of many of these
data appear in Astronomical Phenomena.
- Section C: SUN
Mean orbital elements, elements
of rotation; ecliptic and equatorial coordinates; heliographic coordinates,
horizontal parallax, semi-diameter and time of transit; geocentric
rectangular coordinates; low-precision formulae for coordinates of the
Sun and the equation of time.
- Section D: MOON
Phases; perigee and apogee; mean elements of orbit and rotation; lengths
of mean months; geocentric, topocentric and selenographic coordinates;
formulae for libration; ecliptic and equatorial coordinates, distance,
horizontal parallax, semi-diameter and time of transit; physical
ephemeris; low-precision formulae for geocentric and topocentric
- Section E: MAJOR PLANETS
Rotation elements for Mercury, Venus, Mars, Jupiter, Saturn, Uranus,
Neptune and Pluto; physical ephemerides; osculating orbital elements
(including the Earth-Moon barycentre); heliocentric ecliptic coordinates;
geocentric equatorial coordinates; times of transit.
- Section F: SATELLITES OF THE PLANETS
Ephemerides and phenomena of the satellites of Mars, Jupiter, Saturn
(including the rings), Uranus, Neptune and Pluto.
- Section G: MINOR PLANETS AND COMETS
Osculating elements; opposition dates; geocentric equatorial coordinates,
visual magnitudes, time of transit of those at opposition.Osculating
elements for periodic comets.
- Section H: STARS AND STELLAR SYSTEMS
Lists of bright stars, double stars, UBVRI standard stars,
uvby and Hβ standard stars, radial velocity standard stars,
variable stars, bright galaxies, open clusters, globular clusters, ICRF
radio source positions, radio telescope flux calibrators, X-ray sources,
quasars, pulsars, and gamma ray sources.
- Section J: OBSERVATORIES
Index of observatory
name and place; lists of optical and radio observatories.
- Section K: TABLES AND DATA
Julian dates of
Gregorian calendar dates; selected astronomical constants; reduction of
time scales; reduction of terrestrial coordinates; interpolation methods.
- Section L: NOTES AND REFERENCES
- Section M: GLOSSARY
- Section N: INDEX
The Astronomical Almanac Online pages are available
at USNO and
HMNAO. Online data are provided for
several years. The latest update to The Astronomical Almanac Online
provides data that accompanies the 2018 edition of The Astronomical
Almanac. The site includes sections on Besselian and second-order day
numbers, lunar polynomial coefficients, satellite offsets, apparent
distances, position angles, eclipses and occultations of Galilean satellites,
bright stars, photometric standard stars, selected X-ray and gamma ray
sources, a full list of Observatories, errata and the glossary.
© HM Nautical Almanac Office,
UK Hydrographic Office, 2006-2021
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