hour circle

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

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Collins
World English Dictionary
hour circle
 
n
a great circle on the celestial sphere passing through the celestial poles and a specified point, such as a star

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

hour circle

in astronomy, any great circle (similar to longitude) on the celestial sphere that passes through the celestial poles-i.e., is perpendicular to the celestial equator. The declination of a celestial object is measured along its hour circle. The hour circle that at any moment is passing through an observer's zenith is his meridian.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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