Corona of the Moon
February 06, 2002
The above photograph shows a very impressive corona (crown) of the full Moon, taken on January 28, 2002 (a telephoto lens was used). Unlike rainbows, which result from refracted and reflected light in water droplets, the corona is produced by diffraction. Tiny water droplets or ice crystals in clouds may interfere with light rays and produce interference rings. The size of the rings depends not only on the wavelength of light but also on the size of the droplets or crystals - smaller droplets produce larger rings. A corona is usually bluish near the Moon and often terminates in a reddish outer ring. This aureole of light may vary in intensity and in the number of rings visible. It's a common diffraction phenomenon often seen around the Sun and Moon. However, rarely are they as vivid as the one shown above.