Moon Halo, February 28, 2007. As I shut down the house at the end of the day I always take a quick look at the night sky. Even if no special celestial events are predicted there is always a chance for an ephemeral event taking place like northern lights, or in this case an ice crystal halo around the Moon. On this night the Moon was at waxing gibbous phase, and thin, high altitude cirrus clouds were passing in front of it. When conditions are just right the countless hexagonal shaped ice crystals in the cloud will act like tiny prisms that bend the moonlight into a spectrum. This spectrum forms a ring, or halo 22 degrees away from the Moon.
The two stars to the upper right of the Moon are Pollux and Castor, the "head" stars of the Gemini Twins. Saturn is located to the left of the Moon, just clearing the branches. When this photograph was taken the bright star Procyon was located 22 degrees away from the Moon to the lower right, so its light shines through the halo. A great horned owl was calling in the woods while I took this photo.
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