In meteorology, a corona is produced by the diffraction of light from either the Sun or the Moon through a cloud of water droplets. It consists of a series of concentric colored rings which appear around the celestial object but which are actually at cloud height. Coronae differ from haloes in that the latter are formed by refraction from ice crystals. Reddish colors always occupy the outer part of a corona's ring.
See also: Atmospheric diffraction