Hour-circle definitions

A great circle passing through the poles of the celestial sphere and intersecting the celestial equator at right angles.
noun
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Any great circle of the celestial sphere which passes through the celestial poles and is therefore perpendicular to the celestial equator.
noun
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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.
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