Atmospheric optical phenomena

[lpetrich]

I've seen halos around the Sun, halos with sundogs, a few times when the Sun was low in the sky in winter. I also once saw this:

Here is a UFO that I once saw. I was traveling by airplane from Newark NJ to Ithaca NY in the winter, and I saw on the clouds a whitish spot that looked like a reflection off of a glass or clear-plastic pane. But there was no such pane in evidence, and my location was an unlikely one for such a pane. It would have to be huge. The spot sometimes flickered, but usually stayed constant in brightness. An extraterrestrial spacecraft following my plane? I decided that the clouds below my plane had an odd property: they had specular reflection in addition to diffuse reflection. I later found out that this was due to ice crystals in the clouds getting oriented as they fell. They have hexagonal symmetry, allowing them to have different optical properties in the horizontal and vertical directions. Others have seen this effect, and photographed it, and it is called a "subsun".

The halos and sundogs are also due to ice crystals.