Blue Moon, You Saw Me Kind of Confused

There's a great big old moon up there tonight, and in addition to being beautiful, it's also pretty unusual. In fact, this is the really unusual Blue Moon -- the third moon in a four-moon season -- instead of the more commonly defined Blue Moon, which is when two full moons fall within the same month. I learned about this in an article by Joe Rao, skywatching columnist for Space.com, and you can read all the details here. But the gist of what Rao had to say was this: There are two definitions for the term Blue Moon, and tonight's moon fits the older, more authentic definition.

So far this fall we have had three full moons, counting tonight's: September 23, October 22, and November 21. The next moon will turn full at 3:13 a.m. EST on December 21, beating the winter solstice by 15 hours and 25 minutes, thus becoming the fourth full moon of autumn. Typically, each season has three full moons, each with its own name: early season, mid season, and late season. When a fourth full moon occurs, the third one is designated "blue" so that the fourth and final one can continue to be called the late moon.

Rao never tells us why the word "blue" was chosen to designate this moon. He does tell us, however, that this extra full moon of the year created great consternation for the monks who had charge of a calendar based on three full moons for each season, 12 in a year. A year with 13 moons thus caused the monks scheduling confusion, and that may be how the number 13 came to be considered unlucky.

As for me, I felt pretty lucky to catch this moon in its rising, coming up through the trees across the street from my house. An hour or so later the clouds had thickened to where no moon could be seen.