Walked out of class this morning and was greeted by one of the best iridescence displays I've ever seen! This iridescent corona formed on the leading edge of a long stretch of cirrocumulus. I'm no optics expert, but I'm guessing the colors were particularly vivid on the edge since the clouds were newly formed and therefore likely had particles of similar shape/size. It was incredible how distinct the bands of colors were even when zoomed in at 300mm!
Photo details: Canon 60D, 75-300mm telephoto, f/16.0, ISO 100