right ascension

American  

noun

Astronomy.

1. 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.

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right ascension British  

noun

1.  α.  astronomy 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 Compare declination

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right ascension Scientific  

1. 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.

2. See more at equatorial coordinate system

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Etymology

Origin of right ascension

First recorded in 1585–95

Example Sentences

But the flight control team can read out data describing the orientation of the telescope — for example, “32 degrees right ascension, 12 degrees declination.”

From Washington Post • Aug. 26, 2022

What is the right ascension and declination of the vernal equinox?

From Textbooks • Oct. 13, 2016

What is the right ascension and declination of the Sun at noon on the summer solstice in the Northern Hemisphere?

From Textbooks • Oct. 13, 2016

What is the right ascension and declination of the autumnal equinox?

From Textbooks • Oct. 13, 2016

Exercise 10.—The right ascension of the sun may be found by observing with the sidereal clock the time of its transit over the meridian.

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