Blue moon seen from Istanbul
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Striking images of 'blue moon' from around the world

There has been a rare opportunity to witness a lunar event in the night sky, a so-called "blue moon".

When two full moons are seen within a single calendar month, the second is called a blue moon.

It is a quirk arising from the interaction of the lunar cycle - around 29.5 days - and the human calendar in which months range from 28 to 31 days long.

The next blue moon is not due until 2018.

  • 01 Aug 2015
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