Sunday Night Sun Dog

June 23rd, 2013 at 9:56 pm by under Weather
Sun Dog over Cedar Park - Jim Berry

Sun Dog over Cedar Park – Jim Berry

Some of our viewers spotted a sun dog Sunday evening. Here’s more information about sundogs, courtesy the University of Illinois at Urbana-Champaign:

Sundogs mock suns or parheliaSundogs, also known as mock suns or “parhelia”, are a pair of brightly colored spots, one on either side of the sun.

 


Photograph by: Rauber
Sundogs form as sunlight is refracted by hexagonal plate-like ice crystals with diameters larger than 30 micrometers and their flat faces horizontally oriented.

Sun dogs are visible when the sun is near the horizon and on the same horizontal plane as the observer and the ice crystals. As sunlight passes through the ice crystals, it is bent by 22 degrees before reaching our eyes, much like what happens with 22 degree halos. This bending of light results in the formation of a sundog.

The difference between sundogs and halos is the preferential orientation of the ice crystals through which the light passes before reaching our eyes. If the hexagonal crystals are oriented with their flat faces horizontal, a sundog is observed. If the hexagonal crystals are randomly oriented, a halo is observed.

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