The full moon that was visible on Oct. 31 is called the blue moon because it’s the second full moon of the same month — following the harvest moon of Oct. 1 through Oct. 3. And in a rare treat, the 2020 Halloween full moon will be visible to the entire world, rather than just parts of it, for the first time since World War II.  The last Halloween full moon visible around the globe came in 1944.

Photo by Larry Zieman