Parhelic Arc Over Marietta, Georgia

November 09, 2010

Photographer: Thomas Faber
Summary AuthorThomas Faber; Jim Foster

The photo above showing a very bright section of the parhelic circle and an infrequently observed 120 degree parhelion was taken a few miles east of Marietta, Georgia, on October 30, 2010. The parhelic circle is produced when sunlight reflects off of the nearly vertical faces of plate-shaped ice crystals that compose cirrus clouds. If intact it encircles the sky at the same altitude as the Sun -- passing through the Sun itself. The pale colored "tail" often seen on many sundogs is in fact part of the parhelic circle. Note that the rarer 120 degree parhelion is found on the opposite side of the sky from the Sun (120 degrees from the Sun) and results from multiple reflections inside thickened portions of similarly aligned plate crystals. Whenever you happen to see a brilliant sundog make sure to look for the 120 degree parhelion. Photo taken at 2:30 p.m. Eastern Daylight Time.

Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot SX100 IS; Focal Length: 12.8mm; Aperture: f/4.0; Exposure Time: 0.0013 s (1/800); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No; Color Space: sRGB.