A slightly past full moon on Halloween

¡SkyCaramba! Weekly astronomy blog for the week ending October 27, 2012

The moon will be full on October 29 this year. It will have begun waning by the time Halloween arrives. It’ll still be full enough for many people to think of it as a full moon. Look closely, though, and you’ll see the shadow edge has already started to come around on the moon’s western limb.

I’ve put together a list of full moons that happened or will happen on October 31 or November 1, Universal time, during the 20th and 21st centuries. November 1 is included because that’s the date already when it’s still the evening of October 31 in the western hemisphere.

The moon was full for Halloween in 1906, 1925, 1944, 1952, 1955, 1963, 1974, 1982, 2001, 2020, 2039, 2058, 2077, 2085, and 2096.

Notice how there’s as little as three years and as much as 19 years between Halloween full moons. The full moon itself happens every 29.5 days. But our calendar is a bit irregular. One month has just 28 days and sometimes 29. A few have 30 days. Most have 31. These irregularities make for 14 possible calendars to go on top of that lunar cycle.

Happy Halloween. ¡SkyCaramba!