The cloud was quite cooperative. Not at all like the Crestone and dunes image--there the clouds kept moving over Crestone obscuring its rugged outline. And clouds outside the image kept blocking the light from the setting sun, eliminating the shadows on the dunes. Had to wait 30-minutes before the light seemed just right when I took that one!
Bottom line: Getting a good image is as much luck as it is skill and art! --mark d.