I came home from class the other night and noticed some strange halo around the moon. So I grabbed my camera to get the pictures below at various exposure levels.
This is not lens flare. Or at least not from the camera, The bright dot under the moon is I think, but not the ring. I took the picture only because I noticed it through my own eyes. My only thought would be maybe the atmosphere somehow acted as a “lens” of it’s own and it was “flare” on the overcast sky, but then again I have no idea what I’m talking about. Couldn’t be a natural cloud formation. Way too uniform.
Saw those rings around the moon all the time in the winter growing up in Wisconsin. They were usually a good sign that snow was on the way in coming day or two.
I remember that’s why my parents always told us. Kinda surprisingly, though. My mom’s a doctor (biologist) and my dad’s a physicist. And I don’t think the halo-snow coincidence is supported by any hard science. Or is it?
The halo is caused by ice crystals in cirrus clouds. There are often a lot of cirrus clouds in front of storm systems. An oncoming storm produces conditions that are favorable for halos. In the winter in Wisconsin, my understanding is that a storm system is more likely to produce snow than rain.
You say the blue dot is a lens flare; yet, why is it in different locations in the consecute photos? I guess I am assuming the photos were taken back-to-back. …Did you take the moon photos at different times of the night?
Not quite – there’s a subtle but profound difference between a 22 degree halo and a sun dog.
The halo is caused by randomly oriented crystals, with the rays passing between faces that make a 60 degree angle with each other. (Usually these are the non-adjacent faces of hexagonal rods or plates, but there ARE cases where the plate has an equilateral triabgle cross-section).
Sun dogs are caused by plates (or, rarely, hexagonal rods) that are oriented so that the hexagonal cross=section is horizontal. Hence, they appear as blobs of light on either side of the sun (if there happen to be ice crystals there). When the sun is on the horizon, the sun dogs lie right on the 22 degree halo. But as the sun rises, the sun dogs start to move outside the 22 degree halo, always remaining level horizontally with the sun. They are rarely seen above a few tens of degrees, and they vanish above 40 degrees due to total internal reflection.
You can get lunar equivalents of sun dogs – called "moon dogs’ or “paraselenae”, but they’re much rarer.
Sun dogs, on the other hand, are incredi9bly common. They’re more common than rainbows, although most people don’t know to look for them.
