Sun, Halo and Shadow
|Aug, 3rd, 1993
|St. Goar, Germany
© 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.