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

This event is also a conjunction, which in astronomy means that the planets share the same right ascension.

From The Guardian

Bessel’s practice was to unclamp in declination, lower and read off the head, and then restore the telescope to its former declination reading, the clockwork meanwhile following the stars in right ascension.

From Project Gutenberg

Hipparchus was an accurate observer, and he discovered an apparent and perpetual shifting of the vernal equinox westward, by which the right ascensions of the stars are all the time increasing.

From Project Gutenberg

The measurements that correspond in astronomy to terrestrial latitude and longitude are called declination and right ascension and are obviously made with reference to the celestial equator, not the ecliptic.

From Project Gutenberg