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.
"hour circle." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (September 22, 2018). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/hour-circle
"hour circle." The Columbia Encyclopedia, 6th ed.. . Retrieved September 22, 2018 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/hour-circle