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hour angle

(Encyclopedia)hour angle, in astronomy, a coordinate in the equatorial coordinate system. The hour angle of a celestial body is the angular distance, expressed in hours, minutes, and seconds (one hour equals 15 deg...

Picard, Jean

(Encyclopedia)Picard, Jean, 1620–82, French astronomer, noted for having made the first accurate measurement of a degree of the earth's meridian. The figures he established were of great value to Newton in his ca...

ephemeris

(Encyclopedia)ephemeris ĭfĕmˈərĭs [key] (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 th...

Celsius, Anders

(Encyclopedia)Celsius, Anders änˈdərs sĕlˈsēŭs [key], 1701–44, Swedish astronomer. While professor of astronomy at the Univ. of Uppsala (1730–44), he traveled through Germany, France, and Italy, visiting...

Lacaille, Nicolas Louis de

(Encyclopedia)Lacaille, Nicolas Louis de nēkôläˈ lwē də läkäˈyə [key], 1713–62, French astronomer. As a result of his success in making meridional measurements in France under the patronage of the duke ...

McCarthy, Cormac

(Encyclopedia)McCarthy, Cormac, 1933–2023, American novelist, b. Providence, R.I. He grew up in Knoxville, Tenn., moved to the Southwest in 1974, and since then mai...

celestial pole

(Encyclopedia)celestial pole, one of the two points at which the earth's axis of rotation intersects the celestial sphere. The celestial pole is important as a reference point in the equatorial coordinate system; t...

Pickering, Edward Charles

(Encyclopedia)Pickering, Edward Charles, 1846–1919, American astronomer and physicist, b. Boston, grad. Harvard (B.S., 1865); brother of W. H. Pickering. He was professor of physics (1868–77) at the Massachuset...

sidereal time

(Encyclopedia)sidereal time (ST), time measured relative to the fixed stars; thus, the sidereal day is the period during which the earth completes one rotation on its axis so that some chosen star appears twice on ...

Royal Greenwich Observatory

(Encyclopedia)Royal Greenwich Observatory, astronomical observatory established in 1675 by Charles II of England at Greenwich and known as the Royal Observatory. It moved during 1948–57 to Herstmonceux Castle, Su...