Desert Dogs

June 29, 2012


Photographer: Rick Scott; Rick's Web site 
Summary Author: Rick Scott; Jim Foster

The photo above showing two equally vivid sundogs was observed just before sunset from near Marble Canyon in northern Arizona. Note that an upper tangent arc is also faintly visible. Sundogs, halos and their kin are optical phenomena that result from the interplay of sunlight (or moonlight) and ice crystals in the atmosphere, predominantly in cirrus clouds. Sundogs form when light refracts through oriented, plate-shaped, hexagonal ice crystals. Upper tangent arcs are the result of light refraction through columnar ice crystals. When you detect a sundog (also called mock sun or parhelion), it's because sunlight has entered through one of the side faces of the crystal and exited through an alternate side face, which is angled 60 degrees to the one it first entered. Photo taken on October 14, 2011.

Photo details:  Camera Maker: Canon; Camera Model: Canon EOS 40D; Lens: EF16-35mm f/2.8L USM; Focal Length: 19mm; Focus Distance: Infinite; Aperture: f/8.0; Exposure Time: 0.0013 s (1/800); ISO equiv: 100; Exposure Bias: none; Metering Mode: Matrix; Exposure: Manual; Exposure Mode: Manual; White Balance: Manual; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB; Software: Adobe Photoshop CS5 Windows.