Starwatch: Autumnal equinox in northern hemisphere, spring in the south

Precise moment of equinox in UK is 1.05am on Wednesday – but day and night will not be equal until Friday

Starwatch: Autumnal equinox in northern hemisphere, spring in the south

TL;DR

  • The autumnal equinox occurs this week, marking the astronomical start of autumn in the northern hemisphere and spring in the southern hemisphere.
  • The precise moment of the equinox is at 01:05 BST on September 23rd.
  • Contrary to popular belief, day and night are not exactly equal during the equinox.
  • This is due to the sun appearing as a disc and atmospheric bending of its rays, making daytime slightly longer.
  • The equilux, or 'equal light,' when day and night are closest to being equal, will occur around September 25th in the UK.

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