Circumzenithal Halo Fragment
June 03, 2007
Sometimes referred to as a false rainbow, the circumzenithal arc shown above was captured over Moscow, Pennsylvania on August 10, 2007. Hexagonal plate-shaped ice crystals having a similar orientation produce these cheerful arcs. Their vivid colors are produced by the refraction of light rays passing through the 90° prisms of the plate crystals -- light enters upper horizontal faces and passes out through vertical sides. Unlike circumhorizontal arcs, the Sun need not be high in the sky to observe these beauties. Photo taken a little past 7:00 p.m. (Eastern Daylight Time).