celestial meridian


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celestial meridian,

vertical circlevertical circle,
in astronomy, the great circle on the celestial sphere that passes from the observer's zenith through a given celestial body. In the altazimuth coordinate system the altitude of a body is measured along its vertical circle.
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 passing through the north celestial pole and an observer's zenithzenith,
in astronomy, the point in the sky directly overhead; more precisely, it is the point at which the celestial sphere is intersected by an upward extension of a plumb line from the observer's location.
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. It is an axis in the altazimuth coordinate systemaltazimuth coordinate system
or horizon coordinate system,
astronomical coordinate system in which the position of a body on the celestial sphere is described relative to an observer's celestial horizon and zenith.
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.

celestial meridian

See meridian.

Celestial Meridian

 

a great circle of the celestial sphere passing through the celestial poles and the zenith of the observing site. The celestial meridian intersects the celestial horizon at the south and north points.

celestial meridian

[sə′les·chəl mə′rid·ē·ən]
(astronomy)
A great circle on the celestial sphere, passing through the two celestial poles and the observer's zenith.

celestial meridian

celestial meridianclick for a larger image
Semi–great circles produced by projecting the earth's meridian onto the celestial sphere. Each earth's meridian has its corresponding celestial meridian. The celestial meridian of any place on the earth is the great circle of the celestial sphere that passes through the celestial poles, zenith, and nadir and intersects the horizon exactly north and south. As the celestial sphere and the stars rotate, the celestial meridian remains fixed. Astronomical bodies change their celestial meridians continually with time.