Sun Halo and Ice Crystals
© Copyright by the observers
The image above shows a 22 degree halo. Such halos result from sunlight being
refracted by hexagonal ice crystals. This one is particular
interesting since the halo is very close, so close that you actually can
see the tiny ice particles as luminous specks, also called "diamond dust".
See also:
M.G.J. Minnaert: "Light and Color in the Outdoors", Springer-Verlag
Les Cowley: Atmospheric Optics web
site about halos
