Lunar Halo Above Somogy, Hungary
May 02, 2010
The photo above showing a captivating 22 degree lunar halo was taken at Somogy, Kaposfő, Hungary on January 25, 2010. On this winters night, randomly oriented ice crystals in thin cirrus clouds refracted the light of the waxing, gibbous Moon into a perfectly formed circle having a radius of 22 degrees. This circle is always the same size and is caused by the minimum deviation of moonlight or sunlight through 60 degree, pencil shaped prisms (ice crystals). Light passing through crystals at angles where it's minimally deviated is quite concentrated – bright enough to be observed as a halo if the crystals are poorly aligned. The bright object to the upper left of the Moon is Capella; the principal star in the constellation of Auriga.
Photo details: Canon EOS 1000D camera; fisheye lens; ISO 400; f6.3; 30 second exposure; 7:50 p.m. local time.