The Moonbow phenomenon at Yosemite Falls

The full moon of June 26, 2010 shining on Yosemite Falls in Yosemite National Park has the potential to produce the brightest moonbow of the year.  What is a moonbow?  Just like a rainbow, a moonbow is produced by light refracting off water - in this case, moonlight and a waterfall.  The mist from Upper and Lower Yosemite Falls produces moonbows on a regular basis.  To an observer, the moonbow appears white or silvery, but extended time exposure photography reveals colors exactly like a solar rainbow.

The sighting of the elusive moonbow through the centuries was left to chance until a professor at Texas State University in San Marcos devised a computer model that could predict the appearance of moonbows in places like Yosemite Falls.  Astronomer Don Olson led a group of honors students in the project that required calculus, spherical trigonometry and computing.

According to the schedule posted by Texas State, the full moon of June 25 and 26 has the potential to create the brightest moonbow based on spring runoff and the volume of the falls.  Since Yosemite had a heavier-than-normal snowpack this past winter with cool Spring temperatures including snowfall in May, the volume of Yosemite Falls is still very high.  View the moonbow at Lower Yosemite Falls by taking the paved path that leads to the Lower Falls amphitheater.  Viewing the moonbow at Upper Yosemite Falls is best from the Sentinel Bridge shuttle stop parking lot just outside Yosemite Village.

The moonbow will be visible once the moon has risen above the cliff walls of Yosemite Valley after 11:00 PM.