ephemeris(redirected from ephemerides)
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ephemeris(ĭfĕm`ərĭs) (pl., ephemerides), table listing the position of one or more celestial bodies for each day of the year. The French publication Connaissance de Temps is the oldest of the national astronomical ephemerides, founded in 1679. The Nautical Almanac and Astronomical Ephemeris (usually abbreviated to the Nautical Almanac), an annual publication by the British Royal Observatory at Greenwich since 1767, has been a leading compilation of ephemerides since its inception. Its original purpose was to provide the astronomical information necessary to derive longitude at sea. In 1852 the U.S. Naval Observatory began publishing a book called the American Ephemeris and Nautical Almanac, which contained similar information to that published at Greenwich but adjusted for the meridian at Washington, D.C. Beginning with the edition for 1958, Great Britain and the United States, in a joint effort, issued ephemerides that are identical in content, although they remain separate publications with different names (the British volume was renamed The Astronomical Ephemeris); in 1981 the British and American publications were combined as The Astronomical Almanac. This ephemeris (adapted to the Greenwich meridian) is issued well in advance of the dates covered and contains such information as the daily right ascension and declination of the sun, moon, planets, and other celestial bodies, and daily data on the sunrise, sunset, moonrise, and moonset. Among other publications issued are The Ephemeris (U.S.) and The Star Almanac for Land Surveyors (Brit.), which are star ephemerides used by surveyors, and the Air Almanac (Brit./U.S.), used in air navigation. By international agreement the basic calculations of astronomical ephemerides are shared among a number of countries including France, Germany, Spain, and Russia. The Ephemerides of Minor Planets is compiled and published annually by the Institute of Theoretical Astronomy, St. Petersburg (formerly Leningrad). In addition, the International Astronomical Union issues ephemerides for every newly discovered comet and for many newly found asteroids. Through the Minor Planet Center in Cambridge, Mass., astronomers can obtain ephemerides of any asteroid or comet.
ephemeris(i-fem -ĕ-riss) (plural: ephemerides)
Ephemeris(religion, spiritualism, and occult)
An ephemeris (pl., ephemerides) is an astronomical/astrological almanac listing the daily positions of the Sun, the Moon, and the planets, as well as other information, including, in astrological ephemerides, certain information necessary for calculating an astrological chart. The word is derived from the Greek ephemeros, meaning “existing no longer than a day,” from which the word “ephemeral” is also derived.
The use of such tables is very old, and ephemerides are used by navigators, astronomers, and astrologers. During the nineteenth century and the early twentieth century, most of the readily available ephemerides listed planetary positions for noon at Greenwich, England (0° longitude). By the late twentieth century, however, ephemerides had proliferated to the point that tables of planetary positions for midnight Greenwich Mean Time and noon and midnight Eastern Standard Time (North America), sidereal ephemerides, and heliocentric (Sun-centered) emphemerides were all readily available. The personal computer revolution has partially eliminated the need for such tables, as ephemerides have been incorporated into chart-casting programs.
a table or collection of tables containing the values of variable astronomical quantities computed for a series of consecutive moments of time. The most commonly used ephemerides contain the coordinates of stars, planets, comets, artificial earth satellites, and the like and are used in observations of these celestial objects. Special ephemerides also contain information on the velocities of celestial objects and their brightness and other information necessary to organize observations. Ephemerides are computed on the basis of the mathematical theories of the motion of celestial objects.
ephemeris (plural, ephemerides)
ii. A great-circle path scribed on the celestial sphere by the passage of a celestial body or satellite. The path or predicted path of a satellite.