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   Circumscribed Halo  

 
  Oval Circumscribed Halo and 22º Halo around a 54º high sun. Montage of photographs taken by Martha Dawson of Squaw Valley, California over a HaloSim simulation. Photos ©2003 Martha Dawson
 

The circumscribed halo is typically a brightly coloured oval around the sun. It is tangential to the inner 22º halo directly above and below the sun and it is brightest there. Sometimes local brightenings of the 22º halo are the only sign of it. Its shape depends very much on the solar altitude ~ view an animation.

When the sun is lower than 29º the halo separates into the upper and lower tangent arcs. The same rays and crystals form it.