Richt ascension
Richt ascension (abbreviatit RA; seembol α) is the angular distance measured eastle alang the celestial equator frae the vernal equinox tae the oor circle o the pynt in quaisten.[1] Whan combined wi declination, thir astronomical coordinates specify the direction o a pynt on the celestial sphere in the equatorial coordinate seestem.
An auld term, richt ascension (Laitin, ascensio recta[2]) refers tae the ascension, or the pynt on the celestial equator that 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 contrast wi oblique ascension, the pynt on the celestial equator that rises wi a celestial object as seen frae naur ony ither bit on Yird, whaur the celestial equator intersects the horizon at an oblique angle.[3]
References
[eedit | eedit soorce]- ↑ 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.
- ↑ 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"
- ↑ 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