Published by the Nautical Almanac Office,
United States Naval Observatory and
Her Majesty's Nautical Almanac Office,
The Astronomical Almanac For the Year 1991 provides astronomical data, mainly in tabular form, for use in navigation, surveying, scientific research, litigation, accident reconstruction, and many other activities. Issued annually, the almanacs contain data for one year. It is prepared jointly by the U.S. Naval Observatory and Her Majesty's Nautical Almanac Office, United Kingdom Hydrographic Office.
TABLE OF CONTENTS
Corrections and changes to recent volumes
List of contributors
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, use of Besselian elements.
Section B TIME-SCALES AND COORDINATE SYSTEMS
Calendar; chronological cycles and eras; religious calendars; relationships between time scales; universal and sidereal times; reduction of celestial coordinates; proper motion, annual parallax, aberration, light-deflection, precession and nutation; Besselian day numbers; second-order day numbers; rigorous formulae for apparent place reduction; position and velocity of the Earth; mean place conversion from B1950-0 to J2000-0 and from J2000-0 to 131950-0; matrix elements for precession and nutation; polar motion; diurnal parallax and aberration; altitude, azimuth; refraction; pole star formulae and table.
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; daily polynomial coefficients; low'-precision formulae for geocentric and topocentric coordinates.
Section E MAJOR PLANETS
Osculating orbital elements for Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto; heliocentric ecliptic coordinates; geocentric equatorial coordinates; times of transit; rotation elements; physical ephemerides.
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 for periodic comets; geocentric equatorial coordinates and time of transit for Ceres, Pallas, Juno and Vesta; orbital elements, magnitudes and dates of opposition of the larger minor planets.
Section H STARS AND STELLAR SYSTEMS
Lists of bright stars, UBVRI standard stars, uvby and H# standard stars, radial velocity standard stars, bright galaxies, open clusters, globular clusters, astrometric radio source positions, radio telescope flux calibrators, X-ray sources, quasars, pulsars and variable stars.
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; IAU system of astronomical constants; reduction of time scales; reduction of terrestrial coordinates; interpolation methods.
Section L EXPLANATION
Section M GLOSSARY
Section N INDE