Iridescent Cloud Edge Over Colorado

Explanation: Sometimes your eclipse viewing goes bad in an interesting way. While watching and photographing last Thursday 's partial solar eclipse , a popular astronomy blogger suffered through long periods of clouds blocking the Sun. Unexpectedly, however, a nearby cloud began to show a rare effect: iridescence . Frequently part of a more familiar solar corona effect, iridescence is the diffraction of sunlight around a thin screen of nearly uniformly-sized water droplets. Different colors of the sunlight become deflected by slightly different angles and so come to the observer from slightly different directions. This display, featured here , was quite bright and exhibited an unusually broad range of colors. On the right, the contrails of an airplane are also visible.

APOD Wall Calendar: Weather and Volcanoes