When observed, a circumscribed halo is normally oval in shape and, at the points directly below and above the sun, lies tangential to the 22° halo. It form when, as the sun rises, the upper tangent and lower tangent arcs extend into each other and close in on the 22° halo. As the sun rises above 70° it essentially covers the 22° halo.
A circumscribed halo is more intense in colour than the 22° halo. Like many other halos, it is reddish on the inner edge, facing the sun, and bluish on the outer edge. 
- Les Cowley (?). "Circumscribed Halo". Atmospheric Optics. Retrieved 2007-04-15. (includes a composite image of a circumscribed halo)
- "Circumscribed Halo". Arbeitskreis Meteore e.V. Retrieved 2007-04-15. (includes a fisheye photo of the phenomenon)
- www.paraselene.de - HaloSim Computer simulations of a circumscribed halo.
- Atmospheric Optics - Circumscribed Halo - solar altitude - an animation showing how the shape of the phenomenon changes as the sun rises.
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