Friday, May 12, 2006
Bishops' Ring after Pinatubo eruption
After the 1991 Philippinian Pinatubo eruption, a large diffraction corona around the sun became visible worldwide. It was seen for many months in 1992 and 1993. This corona phenomenon is known as a "Bishops' Ring". It appears when sunlight shines through stratosperic layers of volcanic dust. The pattern of light and color is the same as that of the common corona in cloud droplets, consisting of a blueish white aureole directly around the sun, surrounded by a reddish to brownish diffuse and broad ring. The radius, however, is large and comparable to that of the common halo, being typically about 25 degs. This photograph was taken by Peter-Paul Hattinga Verschure, this one with super wide-angle lens and his second with a 20mm, from Deventer in The Netherlands on 29th March 1992. It was a spring day with very transparant air conditions, the best circumstances to see this phenomenon.