Lunar Halo, Orion and Grossglockner

March 27, 2012

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Photographer: Selina and Patrick Hochleitner; Patrick’s Web site
Summary Author: Patrick Hochleitner and Selina Hochleitner; Jim Foster

The photo above shows a 22 degree lunar halo about a waxing, gibbous Moon, the constellation of Orion and a mid-winter landscape in the Fusch Valley of east-central Austria. In the far background (bottom center) is Grossglockner, Austria’s highest mountain at 12,460 ft (3,798 m). Fusch an der Grossglocknerstrasse is the town at the end of the valley. Halos such as this one form in cirrus clouds composed of randomly oriented, hexagonal ice crystals. Moonlight passes through the side faces of these crystals, is refracted 22 degrees and then exits through alternate side faces. Note the innermost band of the halo is tinted red -- red light is bent less than the other visible colors of light.

Photo details: Nikon D5000 camera; Wallimax Pro Fisheye Lens; ISO 400; F 5.6; 25 second exposure; snapped at 9:00 p.m. local time.