This is a great bit of info that my father-in-law sent to me about the "sunbow." The real name for the "sunbow" is a circumzenithal arc or Bravais' arc. It has also been called "a smile in the sky." It is formed by refraction of sunlight through horizontally-oriented ice crystals, rather than raindrops, and generally in cirrus clouds. Also, it can only form when the sun is at an altitude lower than 32.2 degrees. It is fairly common, says Wikipedia, but is rarely noticed because it's so far overhead. Thanks for sharing Ted!