Astronomy/Cloudless disk around the moon
Hi This is the first time I have ever seen such a thing. See the attached picture. Last night it was cold and cloudy, but there was a cloudless disk around the moon almost perfectly symmetrical in form. It was as if someone had sucked out the clouds around the moon or punched a hole in the atmosphere. What is this phenomena called? It can't be a very frequent occurrence. Sorry the picture is not the greatest, it is done with one of those auto focus automatic cameras.
What you are seeing there is a result of ice crystals in the air--they reflect the light of the moon at a certain angle of incidence, but inside of that angle they don't reflect the light--in fact, they can block it.
I am not sure what the dark spike at the bottom of the photo is--maybe something closer to the ground that also appears in the frame?
Hope that helps