A corona is a glowing white ring edged with blue on the inner side and red on the outer, and seen around the Moon, or less often, around the Sun, usually during eclipses. It is caused by light being diffracted by water droplets in a thin cloud, such as an altostratus cloud. The smaller the droplets of water in the air, the larger the corona will appear.

An anticorona—sometimes called a “glory” or “Brocken bow”—is one or more concentric rings that appear when an object, such as an airplane, casts a shadow on a thin layer of clouds. The anticorona will appear on the side opposite of where the light source (Sun or Moon) is.