Moon Bow at Upper Yosemite Fall

© Moonbow at Upper Yosemite Fall.

A moonbow (also known as a lunar rainbow) is a rainbow produced by light reflected off the surface of the moon rather than from direct sunlight.

Many photographers ascend on Yosemite between April - July during a full moon to capture a moonbow either at the Upper Yosemute Fall, or at the Lower Yosemite Fall.

Several factors are required to capture a Moonbow.

1. Bright Moonlight (nearly-full moon)

2. Moon risen above the south rim of the valley (so moonlight can strike Upper Yosemite Fall)

3. Sufficient mist and spray during snowmelt runoff.

4. Clear skies.

5 Dark skies (Sun more than 9 degrees below the horizon).

6. Geometry (the angle between the "anti-lunar direction" [ observer's shadow cast by the moonlight] and the direction toward the base of the Upper Yosemite Fall must be near the "rainbow angle" of 42 degrees)

This image was made on June 14, 2011 at 10:47 pm

©copyright 2011 Jerry Gilligan All Rights Reserved

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