hour circle
–noun Astronomy. | a great circle on the celestial sphere passing through the celestial poles and containing a point on the celestial sphere, as a star or the vernal equinox. |
Origin: 1665–75
Science Dictionary
hour circle
A great circle passing through the poles of the celestial sphere and intersecting the celestial equator at right angles. An hour circle is equivalent to a meridian on Earth and is used in describing the position of a celestial body with respect to an observer's celestial meridian. See more at hour angle.
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The American Heritage® Science Dictionary
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