On Friday Aug 31st, a Blue Moon will occur. This is the first occurrence since March 2010, and its last until July 2015. Just what is a 'Blue Moon'? Well, it's simply a second full moon in a single month. No it isn't actually blue, but it is a rare event. A Full Moon appears every 29 days due to the regularity of the lunar orbit.
The web-based Slooh Space Camera , is hosting a special broadcast here of the Blue Moon on Friday, beginning at 6 p.m. EDT (2200 GMT).
Usually months have only one Full Moon, but occasionally a second one sneaks in. Full Moons are separated by 29 days, while most months are 30 or 31 days long; so it is possible to fit two Full Moons in a single month. This happens every two and a half years, on average: