Saturday, June 22, 2013

Yosemite Falls, upper and lower, with a lunar rainbow, or moonbow, with stars.




The mist from Yosemite Falls can turn moonlight into a moonbow, or lunar rainbow, around the time of the full moon. It also depends on how much precipitation the area had during the winter and sping, since the misting water droplets coming off the falls is what separates the white light into the spectrum of colors. The moon-caused bow is dim enough that human eyes can't distinguish the colors. We have rods and cones in our eyes, cells that respond to light. The rods respond to brightness and don't detect color, but the cones do respond to color, but only if their light has enough intensity. Moonlight isn't usually intense enough to trigger the cones. When looking at this moonbow, we only saw an arc of ghostly white light, but the camera's time exposure, 30 seconds, does pick up the colors that our eyes can't see.

This perspective also includes the upper falls and stars so that it's easier to tell that it was taken at night. To get here, you have to be willing to do a little scrambling off of the paved path over granite that is sometimes slick, right up to the base of the cliffs, but it's well worth it. You also should bring along a dry cloth to wipe the droplets off of your lens, since it will get wet. Wearing rain gear to keep yourself dry and protected from the wind is a good idea, too. Waterfalls create their wind. The falling water drags air down with it. 

This image was two shots, lower and upper, then merged together to create one larger image. The two were taken on June 2, 2012. We tried again this year, 2013, but last year's results were better.

Remember, it's not just a photo, it's a story!

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