Halo and Space Needle
May 18, 2004
The photo above showing a fine example of a 22 degree solar halo was taken on March 28, 2004 in Seattle, Washington. The Space Needle was used to shield the camera from the Sun. Halos can occur if hexagonal (plate or column-shaped) ice crystals in cirrus-type clouds are more or less randomly oriented. In this case, the cirrus clouds are very faint. Sunlight enters one side of a crystal, is refracted, and then exits the opposite side, where it is again refracted by the same amount and in the same direction as the original refraction.