Sundog and bright tail

The photo above showing a colorful sundog heeling the horizon was taken in Trento, Italy on the afternoon of November 29, 2011.  Photographer: Alessandro Zotta

Sundogs, also known as parhelia or mock Suns, form when plate-shaped, hexagonal ice crystals in cirrus clouds are aligned horizontally. When such an alignment occurs, sunlight passes through the alternate side faces of the crystals, being bent 22 degrees from its original path. The bright tail of this sundog is actually a portion of the parhelic circle. Note that the Sun is behind the mountain face at right — at the same altitude as the sundog.

via epod