22° Halo

The most common of the halos is the 22 degree halo, a colored ring around the sun or the moon with a radius of 22 degrees. It is sometimes called the small halo. It has a fairly sharp reddish inner edge and a diffuse bluish outer region. The 22 degree halo is caused by refraction between faces inclined at 60 degrees in randomly orientated crystals. Like in all halos the light from it is polarized. The 22 degree halo is visible very often, though we are far more likely to see just a section of it than the entire ring. An observer might expect to see this halo once every five days. 

 
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