I have always heard that the only waterfall in Yellowstone where you can see a moonbow is Dunanda Falls deep in the Bechler (southwest corner). After learning the basics of night photography, I got to wondering if that were really true. After doing some research and nearly a year of waiting, I put my theory to the test. This is the result. A moonbow on the Lower Falls of the Yellowstone. The bow didn't appear quite where I thought it would and it appeared later than I thought, but it appeared. I am now wondering if this is more common than we think. I'll have to do more research, and, of course, more photography. Moonbows are formed by the light of the moon (which is reflected sun light). The moon has to be bright (the days surrounding the full moon are best) and at the right angle (about 40 degrees above the horizon). Like their daytime counterparts, the light is refracted and reflected which breaks the light into its component colors. Moonbows appear as white arcs since the colored light is too faint to accivated the color cones in our eyes. Long exposure photography brings out the colors. Moonbows are also called Lunar Rainbows or White Rainbows.
The aurora borealis playing over Yellowstone can happen a couple of times a year on average. Except for this 5 minute burst of brilliant color (called a substorm), the green on the northern horizon was all that was visible while I watched.
