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Iridescent Clouds

Date:4.4.2004 Optics:f=180mm
Place:Tübingen Observer:Till Credner

© Copyright by the observers

Sometimes you may see colorful clouds in the vicinity of the sun. However, you should wear sunglasses and block the direct sunlight to see the effect clearly with no dazzling. Do not look directly into the sun!

Such iridescent clouds appear due to diffraction effects if the clouds water droplets are of similar sizes. Due to the different particle size distribution inside the clouds the colors often follow the clouds shape. But closer to the sun the angular distance to it becomes much more important and such iridescence evolves to a so called Aureole or Corona with concentric rings.

See also:
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