September equinox

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Related to September equinox: December solstice, June solstice


equinoxclick for a larger image
Positions of sun and the earth at spring and autumnal equinoxes.
i. One of the two points of intersection of the ecliptic and the celestial equators, occupied by the sun when its declination is 0°. Also called an equinoctial point. That point occupied on or about March 21, when the sun's declination changes from south to north, is called the vernal equinox, spring 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 the 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. At the time of equinox, the duration of day and night is the same or equal.
ii. That instant the sun occupies one of the equinoctial points.
References in periodicals archive ?
Seasons on Saturn Season Date March equinox 3 March 1980 June solstice 11 December 1987 September equinox 19 November 1995 December solstice 26 October 2002 March equinox 10 August 2009 June solstice 22 May 2017 Table 2.
Next month sees the September equinox - meaning we're halfway from mid-summer and halfway towards midwinter.