A harvest moon is the full moon closest to the autumnal equinox, when night and day are equal in length. And for the first time since 1991, these two events coincided in the small hours of Thursday, in the northern hemisphere.

The northern autumnal equinox officially began at about 0420 BST on 23 September. It will not fall at the same time as the harvest moon again until 2029.

The name "harvest moon" dates from when farmers relied on its bright light to extend the working day. Here, however, it illuminates a moonlit equinox swim in Miami.

This special moon also marked Wednesday's mid-autumn Festival, celebrated by Chinese people worldwide at this time of year.

It's a festival marked with round moon cakes and lanterns to represent the harvest moon, as seen in this Hong Kong park. The shape of the full moon is significant, as the word "round" implies family reunion in Chinese.

And in Germany, the harvest moon comes during the Oktoberfest beer festival. Originally a public celebration of the marriage of Crown Prince Ludwig in 1810, the annual extravaganza also includes agricultural shows to show off autumn's bounty.

Despite centuries of study through increasingly powerful telescopes, the Moon only began to reveal its secrets during the Apollo landings in the 1960s and 70s.

The Moon - as pictured here by Nasa astronauts in 1969 - is the Earth's only natural satellite. It is in synchronous rotation with Earth, always showing the same face. For more info, delve into the BBC archive of Moon clips, linked below.

But knowing the Moon's secrets makes it no less potent a sight. It is the brightest object in the sky after the Sun. Its prominence, and its regular cycle of phases...