Blue Moon – 31st December 2009

This month is a blue moon month!

Commonly speaking, we call a moon ‘blue’ when there are two full moons in the same calendar month. This happens every 2.8 years.

An alternative definition declares a moon to be blue when it is the fourth full moon of a season, marked by equinoxes. This definition was quoted in the “Maine Farmers Almanac” in the 1930’s.

This month there is a full moon on 1st December and on 31st December.  So it will be a blue moon on new year’s eve (hogmanay).

The next blue moon when there are two full moons in one month will be in August 2012.

By the “four in one season” (Maine) reckoning, the next blue moon will occur in November 2010.