Dunanda Falls is on Boundary Creek in the SW corner of Yellowstone Park. It is 150 feet high with several hot springs just below it. The falls faces due south, and because of the mostly clear vertical drop, it creates a lot of mist and spray when the water hits the rocks at the base. During a full moon on a clear night, the moon will create a lunar rainbow in the mist or a moonbow. While I was standing watching the moonbow, it looked like a shimmery silvery blue arch. The digital chip saw the color with long exposures. I was here in 2001 on an assignment for National Geographic and made a few photographs with ISO 100 film which required an exposure time of one minute. I returned on the blue moon in Aug 2012 to use a more sensitive photography device, with an ISO of 800 or more. My exposure times ranged from 8 seconds to 15 seconds. One of the problems was dealing with the mist coming downstream which fogged up the surface of my lenses. Another problem was negotiating the extremely steep hillside in the dark with a small headlamp, in the narrow canyon below the falls. I had scheduled 4 nights around the full moon to be sure I caught it when the night sky was clear.