Coronas and Anticoronas
A corona is a ring of light that surrounds the sun or the moon, sometimes forming a luminous disk with the sun or moon at its center. It may be colored with blue on the inside and red on the outside. Coronas are produced when light waves from the sun or moon are slightly deflected around cloud droplets, causing convergence of light that appears in circles around the sun or moon.
The anticorona or "glory" occurs at the point opposite to the light source and consists of one or more colored rings that appear around the shadow cast by an observer on a cloud or in fog. As seen in the photo below, the anticorona can on rare occasions be observed from an airplane. The observer in the airplane can see the shadow of the airplane on the cloud and the "glory" rings around the shadow.
(Photograph contributed by K. Steffen)
