The bright orange and yellow patch just above the treetops at the right side of this picture is a sundog. When high-altitutude cirrostratus clouds are in the sky, sundogs can often be seen on one or both sides of the Sun. When they appear, they are always at the same height above the horizon as the Sun, 22 degrees to the left or right. They are caused by ice crystals in these clouds, which act like minature prisms.

Image details:  1/1500-second exposure at ISO 1600 with a Canon 400D camera at a focal length of 40 mm.  

November 14, 2010