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Parhelic Circle

Date:24.5.2005 Optics:f = 20 mm
Place:San Negrentino, Tessin, CH Observer:Till Credner

© Copyright by the observers

Sometimes a diffuse white ring can be seen going all around the sky at the same altitude as the sun. In the upper case the sun was high in the noon sky giving a quite small parhelic circle with a radius of about 26 degrees around the zenith. The sun is hidden by the medieval church tower of San Negrentino in Switzerland. The formation of this halo phenomenon takes place due to vertical aligned ice crystal surfaces in high Cirrus clouds.

See also:
further images of Halo phenomena
M.G.J. Minnaert: "Light and Color in the Outdoors", Springer-Verlag
R. Greenler: "Rainbows, Halos, and Glories", Cambridge University Press
L. Cowley: "Atmospheric Optics" web site on the parhelic circle