Equinox (celestial coordinates): Difference between revisions

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In the case of orbital elements for objects within the solar system, only a few of the classical orbital elements are affected by a switch of equinox: the longitude of the ascending node, and (to a much lesser extent) the inclination. If another set of orbital elements are used, such as the position and velocity vectors for a particular epoch, all components can be affected by a switch of equinox.
 
Equinox is often confused with [[Epoch (astronomy)|epoch]] with the difference between the two being that the equinox addresses changes in the coordinate system, while the epoch addresses changes in the position of the celestial body itself. The currently used standard equinox (and epoch) is [[#J2000.0|J2000.0]], which is January 1, 2000 at 12:00 [[Terrestrial Time|TT]]. The prefix "J" indicates that it is a [[#Julian epochs|Julian epoch]]. The previous standard equinox (and epoch) was B1950.0, with the prefix "B" indicating it was a Besselian epoch. Before 1984 Besselian equinoxes and epochs were used. Since that time Julian equinoxes and epochs have been used.<ref name="Equinoccicc">{{cite book |url=httphttps://books.google.escom/books?id=WDjJIww337EC&pg=PA20&lpg=PA20&dq=julian+epoch+equinox&source=bl&ots=p8s-ilXgiV&sig=Y7PYY-JtJ0537ELO8BLJ7nNKjHk&hl=ca&ei=Cv1aSt3LH4_QjAex4bQb&sa=X&oi=book_result&ct=result&resnum=3 |title=Astronomy on the Personal Computer, p. 20 |accessdate=July 13, 2007 |publisher=[[Google books]]}}</ref>
 
Other equinoxes/epochs that have been used include:
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