Smile in the Sky
April 21, 2016
The colorful smile in the sky featured above was snapped over the White Mountains of Alaska. I was scouting this area for a good vantage point to view aurora (I'm in Alaska on an annual aurora photography expedition), and when I looked up, I was greeted by this exquisite circumzenithal arc (CZA), a pair of bright sundogs and a 22-degree halo. A portion of the parhelic circle was also visible. These arcs and halos result when sunlight is refracted by hexagonal ice crystals that compose cirrus clouds. The CZA, also known as the Bravais' arc, is the brightest of all of the ice crystal halos. It forms when sunlight enters the upper basal faces of similarly oriented ice crystals and then exits through one of the crystals' four side faces. The bottom photo is a close-up of the fisheye view at the top.
Photo Details: Top - Camera Model: Canon EOS 6D; 8mm fish-eye lens; ISO 250; Exposure Time: 0.0010 s (1/1000); Software: Adobe Photoshop CC 2015 (Windows). Bottom - same except: 24 mm lens; Exposure Time: 0.0004 s (1/2500).