Hour Circle
Related Category: Astronomy: General
in astronomy, a secondary axis in the equatorial coordinate system.
hour circle
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Hour Circle
A passing through the . The position of the hour circle and the azimuthal coordinate of a celestial body lying on it is specified by its .
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hour circle: a great circle on the celestial sphere that passes through the celestial poles. It is orthogonal to the celestial equator.
Hour Circle (i) A great circle passing through an object and the celestial poles. (ii) The setting circle on the polar axis of an equatorial mount.
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Hour Circle
A great circle passing through the celestial poles - i.e., perpendicular to the celestial equator.
Hourglass Nebula ...
Hour circle
The great circle drawn from the celestial pole through the object and perpendicular to the celestial equator.
hour circle through 1,
Greenwich celestial meridian,
local celestial meridian
principal vertical circle,
prime vertical circle ...
parallactic angle The angle between a body's hour circle and its vertical circle. Also called position angle.
It is measured along the hour circle passing through the celestial object. Declination is usually given in combination with right ascension or hour angle. [S92] ...
If you draw an hour circle -- a circle at the hour angle passing through the north and south celestial poles -- you will find the object 16 degrees north of the intersection of this hour circle and the celestial equator.
Declination is the angular distance on the celestial sphere north or south of the celestial equator. It is measured along the hour circle passing through the celestial object.
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HOUR ANGLE, the angular distance of a heavenly body from the meridian, as measured around the celestial pole. 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.
Right ascension: The equatorial coordinate specifying the angle (usually specified in hours, minutes and seconds), measured eastward along the celestial equator from the vernal equinox to the hour circle passing through an object in the sky.
 See also: Circle, Hour, Astronomy, Equator, Distance
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