Right ascension is measured continuously in a full circle from that alignment of Earth and Sun in space, that equinox, the measurement increasing towards the east.
the First Point of Aries, which is the place on the celestial sphere where the Sun crosses the celestial equator from south to north at the March equinox and is currently located in the constellation Pisces. Right ascension is measured from the Sun at the March equinox i.e. Both right ascension and longitude measure an angle from a primary direction (a zero point) on an equator. Right ascension is the celestial equivalent of terrestrial longitude. Main article: Equatorial coordinate system It contrasts with oblique ascension, the point on the celestial equator that rises with any celestial object as seen from most latitudes on Earth, where the celestial equator intersects the horizon at an oblique angle. When paired with declination, these astronomical coordinates specify the location of a point on the celestial sphere in the equatorial coordinate system.Īn old term, right ascension ( Latin: ascensio recta) refers to the ascension, or the point on the celestial equator that rises with any celestial object as seen from Earth's equator, where the celestial equator intersects the horizon at a right angle. Right ascension (abbreviated RA symbol α) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the ( hour circle of the) point in question above the earth. Right ascension is measured eastward up to 24 h along the celestial equator from the primary direction. The primary direction of the system is the March equinox, the ascending node of the ecliptic (red) on the celestial equator (blue). Right ascension and declination as seen on the inside of the celestial sphere.
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