What is the ring of clouds around the Sun or Moon called?

Haloes are caused by refraction through ice crystals in cirrostratus cloud. The most common is the 22° halo which is a ring around the sun or the moon. Sundogs or moondogs are bright spots which appear sometimes on the 22° halo either side of the sun or moon. There are many different halo phenomena caused by ice crystals with different shapes but most of them are only seen in polar regions. There is a very good site about haloes with some excellent pictures here:

http://www.meteoros.de/indexe.htm

A corona is a series of coloured rings close to the sun or the moon. These are caused by diffraction in altocumulus or cirrocumulus cloud. They are very different from haloes. You will find pictures of those and many other atmospheric optical phenomena on the same site.

It's not a formation of clouds. Instead, it is similar to a rainbow, but caused by the diffraction of light by ice crystals in the upper atmosphere.It could be the halo effect, or also something called a "Sundog" or a "Moondog" (both appear as a ring-like rainbow effect). I think there's a writeup on Wikipedia on sundogs. Anyhow, it's a funny name, isn't it?

It is called "Halo" which results by the refraction of sunlight or moon light by ice crystals present in the high clouds like cirrostratus .Sometimes this phenomenon is called "Carona" which results by the diffraction of sun or moon light by medium clouds like altostratus.

You're thinking of the halo effect:

http://en.wikipedia.org/wiki/Halo_%28optical_pheno...

It's not a formation of clouds. Instead, it is similar to a rainbow, but caused by the diffraction of light by ice crystals in the upper atmosphere.

It could be the halo effect, or also something called a "Sundog" or a "Moondog" (both appear as a ring-like rainbow effect). I think there's a writeup on Wikipedia on sundogs. Anyhow, it's a funny name, isn't it?

not satisfied with the answer given above. Kindly give an elaborate answer, if any one can