Sun Halo – May 4, 2011

Spotted a halo around the sun on May 4th. I’ve seen them around a full moon before, but not around the sun. By obscuring the sun with my hand or my index finger I was able to shoot some reasonably good photos of the phenomenon.

22° halo is a halo, one type of optical phenomenon, forming a circle 22° around the sun, or occasionally the moon. It forms as sunlight is refracted in hexagonal ice crystals suspended in the atmosphere. As the light beam passes through two sides of the prism forming a 60° angle, the angle of minimum deviation is almost 22° (namely, 21.84° on average; 21.54° for red and 22.37° for blue). This wavelength-dependent variation in refraction causes the inner edge of the circle to be reddish while the outer edge is bluish.

Sun Halo 3

Sun Halo

Sun Halo 4

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