Cloud Iridescence Above the Pacific Ocean

November 25, 2008


Photographer: Thomas Faber, Atlanta Astronomy Club
Summary Author: Thomas Faber

This photo shows antisolar iridescence in a layer of clouds over the Pacific Ocean, east of the Hawaiian Islands. It was taken on May 14, 2008 on a flight from Honolulu to Atlanta. We departed Honolulu at about 4:20 p.m. and were about 80 minutes into the flight, with the Sun rapidly sinking behind us, when the iridescence appeared. Iridescence is caused by diffraction of sunlight by minute cloud droplets of nearly uniform size. It’s typically seen in thin clouds in the vicinity of the Sun, and even near the moon. Sometimes they can be detected considerably more distant from the solar disk.

The glory is a diffraction phenomenon that occurs opposite the Sun at the antisolar point. I wasn’t able to see a glory when the iridescence was visible. This was probably because it was blocked from view by the plane's right engine which is visible in the photograph. After the iridescence was no longer visible, however, a faded glory did come into view for a short time.