22 Degree Lunar Halo

October 27, 2004


Provided and copyright by: Laurent Laveder, Optics of the Atmosphere Gallery
Summary authors & editors: Jim Foster; Laurent Laveder

The photo above showing a 22 degree lunar halo was captured above Bretagne, France on the night of October 1, 2004 -- 4 days past the full Harvest Moon. Halos are formed by hexagonal ice crystals in cirrus clouds having no preferred orientation -- minimum deviation of moonlight through more or less randomly oriented 60 degree prisms causes the 22 degree halo. If crystals have a particular orientation (aligned in similar positions), arcs rather than rings of light result.

Tonight there will be a total lunar eclipse, which will be visible from portions of Europe and the eastern two-thirds of North America. When the Earth's shadow covers the lunar disk, the darkened Moon may appear gray, coppery, orange-red, or even bluish -- the proverbial "Blue Moon." This could occur if sufficient ash and soot from wildfires suffuses the lower atmosphere. The partial phase of this lunar eclipse begins at 9:14 p.m. Eastern Daylight Time (EDT). Totality starts at 10:23 p.m. EDT, and the time of deepest eclipse is 11:04 p.m. Totality ends about 11:45 p.m. If you miss this one, the next total lunar eclipse similarly visible across most of North AMerica won't occur until February 2008.

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