hour circle

American  

noun

Astronomy.

1. 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.

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hour circle British  

noun

1. a great circle on the celestial sphere passing through the celestial poles and a specified point, such as a star

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hour circle Scientific  

1. 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.

2. See more at hour angle

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Etymology

Origin of hour circle

First recorded in 1665–75

Example Sentences

It is equal to the angle at the pole between the hour circle through the body and the meridian, but is usually expressed in time.

From Project Gutenberg

The hour circle of any star is the great circle passing through it and perpendicular to the plane of the equator.

From Project Gutenberg

The inclination of the declination axis was determined with a hanging level which had been provided by Mr. Crossley, the hour circle and polar axis being very firmly clamped.

From Project Gutenberg

The sidereal time at any moment is the right ascension of the hour circle which at that moment coincides with the meridian.

From Project Gutenberg

The end of the polar axis B, that has the end turned with a shoulder, is fitted in a hole bored in the center of the hour circle.

From Project Gutenberg