July - lightning You are here: Home Photo gallery Atmospheric optics Ice crystal halos 9o halo


A halo around the sun or moon with a radius of 9 degrees, caused by refraction of light by randomly oriented pyramidal ice crystals. During a unique halo display on May 26, 1999, at Amsterdam, The Netherlands, it appeared even coloured, like the 22-degrees halo. The 9-degrees halo is uncommon but not very rare either. However, it is easily missed because it is very near the sun.

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