This photo was taken after dark, at the base of Lower Yosemite Falls.
A few times a year, in late spring or early summer, the full moon produces a rainbow on the falls.
The biggest challenge, besides focusing in pitch-dark, was getting through the one-minute exposure without someone's flash going off.
The bow in the photo is actually a lot more visible than the actual one; I was pleased to be able to get anything at all in this situation.
After some research, I learned that moonbows often appear pale or white because the light is so low that the eye's color receptors aren't triggered.
More photos from this Yosemite visit here.