Once in a blue moon?

[Zeffer]

I was finding information about the lunar eclipse when they mentioned a blue moon.

What causes one of these or am I missing some metaphorical reference to something else!

http://www.bbc.co.uk/herefordandworcester/content/articles/2007/01/02/stars_january_2007_feature.shtml

[Kai]

Have a look here

http://www.obliquity.com/astro/bluemoon.html

[SteelRat]

Yup - two in one

[Angela]

Apparently the moon actually turned blue in 1883, and stayed blue for 2 years. This was because of all the dust particles from the Krakatoa eruption, thrown up into the atmosphere.

[Kai]

I saw one last night !!!

I forgot to take out the Blue filter in the diagonal

[The Warthog]

While the moon does occasionally turn blue due to atmospheric conditions, a blue moon is said to occur when a full moon occurs twice in the same month. The second full moon is the blue moon. We might get one this month or next, with the full moon being very close to the first of the month.

[barkis]

I could be tickly Pink with Rhubarb stripes, as long as the flippin clouds would leave it alone.

[Zeffer]

Thanks for that, now I can act all intelligent next time I have friends round!

[GordonCopestake]

The next blue moon is June 30th. After that there isn't one until Dec 2009