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

See Examples For:

hour circle

The shaft which it carries is 1/4-in. steel, carrying the hour circle at one end, and at the other the frame for the declination axis which is similar to the other, but somewhat lighter.

From The Boy Mechanic: Volume 1 700 Things for Boys to Do by Popular Mechanics Co.

It is desirable that the hour circle should read approximately zero when the declination axis is horizontal, but this is not necessary for a reason soon to be explained.

From The Boy Mechanic: Volume 1 700 Things for Boys to Do by Popular Mechanics Co.

The hour circle, F, is half of a similar card, with the hours painted underneath, and divided to 20 minutes.

From Scientific American Supplement, No. 601, July 9, 1887 by Various

Right ascension, corresponding to terrestrial longitude, is the angular distance of a heavenly body from the vernal equinox measured on the celestial equator eastward to the hour circle passing through the body.

From Astronomical Lore in Chaucer by Grimm, Florence M.

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

From A Text-Book of Astronomy by Comstock, George C.