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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