hour circle

hour circle, in astronomy, a secondary axis in the equatorial coordinate system. The hour circle of a celestial body is the great circle on the celestial sphere that passes through both the body and the north celestial pole. A star's hour circle is used in determining its right ascension and declination.

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2024, Columbia University Press. All rights reserved.

See more Encyclopedia articles on: Astronomy: General