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Sun, Halo and Shadow

Date:Aug, 3rd, 1993 Instrument:f=28mm 1/2.8
Place:St. Goar, Germany Observer:S. Kohle

© Copyright by the observers

Halos result from sunlight (or moonlight) being bent by ice crystal clouds called cirrus in the atmosphere. In the picture above you can see a 22 degree sun-halo as well as the shadow of a plane's contrail on the cirrus clouds. If you assume the height of the contrail to be 12 km, you can derive the height of the cirrus where the halo formed from simple geometry.