Double sunset

Midsummer double sunset at Chrome Hill in Derbyshire, England. The Sun sets behind the hill (left) before re-emerging (right) to set again in the valley.

A double sunset is a rare astro-geographical phenomenon, in which the Sun appears to set twice in the same evening from a specific viewing-point. A double sunrise may also occur in a similar situation. Such phenomena may have been regarded as significant in prehistoric times, and double sunsets have been discussed in the context of archaeoastronomy by researchers such as Alexander Thom. The different meanings of "double sunset" refer to the solar eclipse, when the most significant phase is observed shortly before or after the geometrical sunset. In turn, an observer might see two moments with the same level of illumination, adequate to typical sunset or twilight conditions. The phenomenon is alternatively called "double sunrise" or "double dusk", "double dawn" and was reported in Shaanxi Province on April 21, 899 BC following morning annular solar eclipse

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