An amazing circumhorizon arc that I saw last May. I had just crossed the street while walking to lunch when I looked up, saw it…and walked back to the office to get my camera!
It started out as just a couple of small segments, but as the clouds drifted into position it quickly grew, and at its strongest it was just long enough to fill the field of view on my camera. There were also a couple of fragments of a 22° circular halo visible at the time.
It looks like a sort of straightened-out rainbow, but it’s actually caused by ice crystals. If the right type of crystals cover the entire sky, this will actually stretch in a circle all the way around the sky, parallel to the horizon.
At times like this, I really wish I had a DSLR, but the point-and-shoot will do in a pinch.
Location: Irvine, California. May 14, 2010, 1:30pm