The Moon, our nearest neighbour is a highlight of the night sky! Sometimes however, it puts on a spectacular show! This picture captured over the Christmas period shows an atmospheric phenomena called a Lunar Corona. The Corona is formed by the diffraction of moonlight or sunlight (or, occasionally, bright starlight or planet light) by individual small water droplets and sometimes tiny icy crystals of a cloud or on a foggy glass surface. In its full form, a corona consists of several concentric, pastel coloured rings around the celestial objects and a central bright area called aureole. The aureole is often (especially in case of the Moon) the only visible part of the corona and has the appearance of a bluish-white disk which fades to reddish-brown towards the edge. The angular diameter of a corona depends on the sizes of the water droplets involved; smaller droplets produce larger coronae. For the same reason, the corona is the most pronounced when the size of the droplets is most uniform. Coronae differ from halos in that the latter are formed by refraction (rather than diffraction) from comparatively large rather than small ice crystals.
