Devoted to atmospheric optics, this Web site offers beautifully illustrated explanations of spectacular phenomena ranging from rainbows to ice haloes. Created by physicist Les Cowley, it features amazing images, along with explanations of how the imaged effects were created by nature. The ice halo section offers downloadable software for simulating various types of halos.
Go to: http://www.sundog.clara.co.uk/atoptics/phenom.htm