Ulloa's ring

From Glossary of Meteorology

Ulloa's ring

(Also called Bouguer's halo.) An infrequently observed, faint white, circular arc or complete ring of light that has a radius of 39° and is centered on the antisolar point.

When observed, it is usually in the form of a separate outer ring around an anticorona.

Tricker, R. A. R. 1970. An Introduction to Meteorological Optics. 192–193.

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