Sundog and Parhelic Circle

April 25, 2006

Parhelc copy

Provided and copyright by: James Kaler, Astronomy Department, University of Illinois
Summary authors & editors: James Kaler

On the photo above, a striking sundog, red on the inside and blue on the outside, shines to the east of the Sun on this early February morning above Urbana, Illinois. The sundog or parhelion is caused by refraction of sunlight through hexagonal ice crystals, most often in cirrus clouds. In addition, a portion of the parhelic circle is also clearly visible. This pale arc, caused by reflection of light from the front faces of oriented crystal, extends further to the east and then continues in the lower picture through a set of stunning icy wisps. To see such delightful colors and arcs, just look up now and then.

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