hour circle

hour circle

Any of a series of great circles on the celestial sphere along which declination is measured. The hour circle of a particular celestial body or point passes through the body or point and the north and south celestial poles. See also hour angle.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

hour circle

[′au̇r ‚sər·kəl]

(astronomy)

An imaginary great circle passing through the celestial poles on the celestial sphere above which declination is measured. Also known as circle of declination; circle of right ascension.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

hour circle

Any great circle joining the celestial poles and passing through a point on the celestial sphere. All celestial bodies are positioned on particular hour circles. Unlike celestial meridians, which remain fixed with respect to the earth, hour circles move with the celestial sphere as it rotates about the earth. Also called a circle of declination or a circle of right ascension.

An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved