Every full moon presents an opportunity for a lunar rainbow at Cumberland Falls State Park, though atmospheric conditions won't always allow it. Clear skies are a necessity for full luminosity and there has to be enough mist from the falls themselves. I chose Autumn as the best season because it's the first and only time I've been lucky, in the three years I've chased this rainbow. We've also had enough rain in this region lately that rolling waters and mist were a given. A lot of patience is required as the moon needs about an hour or so to clear a ridge after moonrise. You'll want to be there well before that to stake out your spot at one of the overlooks. There were about three hundred people the night I went. The sign at the upper overlook states you can't see the moonbow from the lower overlook, but that is where I got my photo. The window of opportunity is somewhat brief, as the moonbow will disappear once the moon rises above 42 degrees. The colors of the moonbow can't be seen by the naked eye and it will appear white.