Circumscribed halo  From Wikipedia, the free encyclopedia Jump
to: navigation, search The upper part of a circumscribed halo.
A circumscribed halo is a type of halo, an optical phenomenon
that circumscribes a related phenomenon, the 22° halo centred on
the sun.  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.[1] As the sun rises above 70° it
essentially covers the 22° halo.[2]  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. [2]     1. ^ Les Cowley (?). "Circumscribed
Halo". Atmospheric Optics. Retrieved 2007-04-15.  (includes a
composite image of a circumscribed halo)   2. ^ a b
"Circumscribed Halo". Arbeitskreis Meteore e.V. Retrieved
2007-04-15.  (includes a fisheye