HALF MOON HALO: This weekend, the Moon is only half full. Nevertheless, it’s a good time to watch for lunar halos. “I saw one last night,” reports Noel Keating, who sends this picture from Ballintra, Co Donegal , Ireland:
“What a vivid halo!” says Keating. “With only a half Moon, I was able to see stars shining brightly inside the ring. They were not washed out by lunar glare. I was really surprised that the halo itself was so intense, as this is the type of halo you normally get only with a full Moon.”
Moon halos are created by ice crystals in high clouds, which catch rays of moonlight and bend them into a 22o ring. Bright full Moons are great at making these halos, but as Keating has shown, a full Moon is not required. Half is plenty.