Blue Moon

The original meaning of a Blue Moon is the third full moon of four in a single season. A fairly rare event. Tonight was one such.

A more modern definition is when there are two full moons in a single month. 

Even rarer is the opposition of Mars, when the Red Planet and the Sun are on opposite sides of the Earth.

You can just see Mars above the moon and to the right. Tomorrow night it will be the brightest it has been for 10 years. The closest approach occurs on May 30.