Richt ascension

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Richt ascension (abbreviatit RA; seembol α) is the angular distance measured eastward alang the celestial equator frae the vernal equinox tae the oor circle o the pynt in question.[1] When combined wi declination, these astronomical coordinates specify the direction o a pynt on the celestial sphere in the equatorial coordinate seestem.

Richt ascension an declination as seen on the inside o the celestial sphere. The primary direction o the seestem is the vernal equinox, the ascendin node o the ecliptic (reid) on the celestial equator (blue). Richt ascension is measured eastward alang the celestial equator frae the primary direction.

An auld term, richt ascension (Laitin, ascensio recta[2]) refers tae the ascension, or the pynt on the celestial equator which rises wi ony celestial object, as seen frae the Yird's equator, whaur the celestial equator intersects the horizon at a richt angle. It is contrasted wi oblique ascension, the pynt on the celestial equator which rises wi a celestial object as seen frae almaist onywhaur else on Yird, whaur the celestial equator intersects the horizon at an oblique angle.[3]

References[eedit | eedit soorce]

  1. U.S. Naval Observatory Nautical Almanac Office (1992). Seidelmann, P. Kenneth, ed. Explanatory Supplement to the Astronomical Almanac. University Science Books, Mill Valley, CA. p. 735. ISBN 0-935702-68-7. 
  2. Bleau, Guilielmi (1668). Institutio Astronomica. p. 65. , at Google books, "Ascensio recta Solis, stellæ, aut alterius cujusdam signi, est gradus æquatorus cum quo simul exoritur in sphæra recta"; roughly translated, "Right ascension of the Sun, stars, or any other sign, is the degree of the equator which rises together in a right sphere"
  3. Lathrop, John (1821). A Compendious Treatise on the Use of Globes and Maps. Wells and Lilly and J.W. Burditt, Boston. pp. 29, 39. , at Google books