right ascension

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.

right ascension

noun

1. 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 α Compare declination

right ascension

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

Word History and Origins

Origin of right ascension¹

First recorded in 1585–95

Example Sentences

The inner vernier is then set to the right ascension of the object which it is desired to observe.

From Project Gutenberg

The sidereal time at any moment is the right ascension of the hour circle which at that moment coincides with the meridian.

From Project Gutenberg

The difference between the observed time and the right ascension, if any is found, is the "correction" of the clock.

From Project Gutenberg

Meantime the estimated movement in three days was 10″ in right ascension, and about a minute, or rather less, towards the north.

From Project Gutenberg

He has never been taught to mark the right ascension of hill-tops, nor to estimate latitude and longitude from the trees.

From Project Gutenberg