right ascension

right ascension

noun Astronomy.
the arc of the celestial equator measured eastward from the vernal equinox to the foot of the great circle passing through the celestial poles and a given point on the celestial sphere, expressed in degrees or hours.

Origin:
1585–95

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World English Dictionary
right ascension
 
n
astronomy Compare declination α the angular distance measured eastwards along the celestial equator from the vernal equinox to the point at which the celestial equator intersects a great circle passing through the celestial pole and the heavenly object in question

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Science Dictionary
right ascension  
The position of a celestial object east of the vernal equinox along the celestial equator. Right ascension is measured in hours, minutes, and seconds from the vernal equinox (0 hours) to the point where a great circle drawn through the object and the north and south celestial poles intersects the celestial equator. Each hour corresponds to 15° of angular distance along the celestial equator for a total of 24 hours. See more at equatorial coordinate system.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

right ascension

in astronomy, the east-west coordinate by which the position of a celestial body is ordinarily measured; more precisely, it is the angular distance of a body's hour circle east of the vernal equinox, measured along the celestial equator. It is often expressed in units of time rather than degrees of arc. Right ascension and declination define the position of a celestial object. The symbol for right ascension is alpha, the Greek letter a (alpha). See also hour angle.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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