posted on Feb, 3 2015 @ 07:56 AM
originally posted by: CranialSponge
a reply to: defcon5
I believe the OP is talking about a dark circle that extends beyond the moondog halo around the moon...
That's part of a moon ring/dog. The whole effect's called a moon ring. If you get image moons at the 3 and 9 o'clock positions, it's a moon dog.
The dark area's created by concentrating the light that would have gone there into the bright ring. It's all one piece. Also, if you look really
carefully, you'll see that the inner edge of the bright ring is reddish - if the moon's light were a bit more balanced spectrally you'd see a rainbow
where the ring is.
op: the thing's caused by a high layer of very thin clouds composed of ice crystals. They're not so thick you can't see through them, unless they're
lit up by the moon light. Then they glow with dispersed moon light and look opaque. Within the center area of the ring, it's dark, because the light's
been diffracted over to the ring structure. With no illumination (or not much) in the middle, you don't SEE the thin layer of cloud and can see stars
through it, because it's not back-lit. So it can look as if there are no clouds there. If the moon weren't up, you'd see a slight haze obscuring the
edit on 3-2-2015 by Bedlam because: (no reason given)