The term blue moon is commonly used metaphorically to describe a rare event, as in the saying "once in a blue moon".

A blue moon is actually a name given to an irregularly timed full moon. Most years have twelve full moons which occur approximately monthly, but each calendar year contains those twelve full lunar cycles plus about eleven days to spare. The extra days accumulate, so that every two or three years there is an extra full moon (this happens every 2.72 years).

* Folklore gave each moon a name according to its time of year. A moon which came too early had no folk name - and was called a blue moon.

* The Farmer's Almanac defined blue moon as an extra full moon that occurred in a season(which would normally have three full moons). If a season had 4 full moons, the 3rd full moon was named a blue moon.

Originally posted by mopusvindictus
Is there any resource which photographically records the phases of the moon and stores them that can be accessed?