Known as moonbows, spray bows, or lunar rainbows, this amazing site at Yosemite Falls comes into alignment only a few days each year. It is produced by moonlight rather than sunlight. For the creation of the lunar rainbow, you need clear skies, enough water in Yosemite Falls to create misty conditions, dark skies, and bright moonlight.
Other than the difference in light source, its formation is exactly the same as for a solar rainbow. It is caused by the refraction of light in many water droplets in the falls, and is always positioned in the opposite part of the sky from the moon relative to the observer.
Moonbows are much fainter than solar rainbows, due to the smaller amount of light reflected from the surface of the moon. Because the light is usually too faint to excite the cone color receptors in human eyes, it is difficult for the human eye to discern colors in a moonbow. As a result, a moonbow often appears to be white. However, the colors in a moonbow do appear in long exposure photographs.
There are several different spots to set up to capture this scene. I took this shot from the walkway at Cook’s Meadow. Yosemite has some of the most amazing scenery in the world.
If you haven’t had the opportunity to go there, put it on your must see list!