Difference between revisions of "Equinox"
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Revision as of 09:31, 9 April 2007
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Equinox
</dt>
1. One of the two points of intersection of the ecliptic and
the celestial
equator, occupied by the sun when its declination is 0�. Also called
equinoctial point.
</dd>
That point occupied on or about March 21, when the sun's declination
changes from south to north, is called vernal equinox, March equinox,
or first point of Aries; that point occupied on or about September 23,
when the declination changes from north to south, is called autumnal
equinox, September equinox, or first point of Libra.
Equinox is
often used to mean vernal equinox, when referring to the origin of
measurement of right
ascension and celestial
longitude.
</dd>
2. That instant the sun occupies one of the equinoctial points.
</dd>
References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
