Superstitious folks, beware! Friday night is one of those "once in a blue moon" evenings, due to the presence of the full moon for the second time this month.
This is the last time until July 31, 2015 that you will have the pleasure of seeing two full moons in one month. There is a blue moon on average once every 2.7 years.
The rarity of a blue moon is due to the orbit of the moon around the Earth. It takes the moon about 29.5 days to revolve around the Earth, and because most months have more than 29 days, sometimes there will be two rotations within the same month.
The first full moon this month was on Aug. 1.