
If you are feeling blue maybe you can blame it on the blue moon that will shine over us tonight (weather permitting).
Tonight will be our second full moon of the month, meaning it is called a blue moon. (Technically, the moon will be full at 9:04pm.) Why is a moon that does not look blue get called a blue moon?
According to Philip Hiscock of the Dept. of Folklore, Memorial University of Newfoundland the saying has been around for more than 400 years! The meaning has changed many times over the years as well.
In Shakespeare's day is had nothing to do with astronomy and had more of a literal meaning (surprise, surprise). It meant rare or absurd event.
The modern definition was adopted in the 1940s. In those days the Maine Farmer's Almanac offered a definition of Blue Moon so convoluted even professional astronomers struggled to understand it. It involved factors such as ecclesiastical dates of Easter and Lent, tropical years, and the timing of seasons according to the dynamical mean sun.
Aiming to explain blue moons to the layman, Sky & Telescope published an article in 1946 entitled "Once in a Blue Moon." The author James Hugh Pruett (1886-1955) cited the 1937 Maine almanac and opined that the "second [full moon] in a month, so I interpret it, is called Blue Moon."
This was not correct, but at least it could be understood. And thus the modern Blue Moon was born.
The interesting thing is there is such a thing as a blue moon... literally!
A blue moon is indeed rare, but can occur if the conditions in the atmosphere are just right. If the air is very damp and moist the water droplets (if they are just the right size) in the atmosphere can scatter the red and green light in the color spectrum. When the white moonbeam passes through a cloud it can turn blue.Water droplets are not the only thing that can change the moons appearance. The other night when I was in S. Georgia the smoke from the wildfires turned the moon red! The smoke that has been over the metro area today could do the same tonight. So, indeed our blue moon could be red!

In addition to the 'blue moon' you can also see Jupiter tonight. All night Jupiter will be the bright object right beside the moon.
Happy sky watching!
--Chris
Thanks to our friends at NASA for help with this entry






Sub-tropical storm Andrea began as low pressure off the North Carolina coast a few days ago, but then began drifting south of all things, into warmer water. Aloft, there was cold air, not warm air, yet the satellite pictures were taking on the familiar swirl pattern of a normal tropical storm. 
