Post by davesenesac on May 22, 2017 17:51:24 GMT -8
On Friday May 19 about 4pm PDT, I was in Yosemite Valley at the famous Tunnel View vista point. The vista point is at the east end of the 4233 foot long Wawona Tunnel that goes through solid granite. It was a sunny clear day and my timing was to be there when the sun was 42 degrees from being directly opposite Bridalveil Fall that will result in a rainbow. Something one can figure out with Sun elevation and azimuth data plus a bit of topographic map trigonometry. At different times of the year a rainbow will occur at a different time or not at all. One can also catch the Bridalveil Fall rainbow about a half hour later by climbing up into the Rockslides talus on the north side of Yosemite Valley. Although many large waterfalls have rainbows, the rainbow that occurs at Bridalveil Fall that some opinion is the World's most beautiful waterfall, is an unusual phenomenon though it is not proclaimed as something tourist should see when they visit the park.
Water leaps from an overhanging level granite stream bed that on the topographic map is dead vertical for at least 600 feet. Accordingly when the water hits the rocks below, considerable splash and mist results. Especially in May with a large snow pack. Peak flows were however a couple weeks early during the first hot weather of spring though this day they were still better than during most years. Online topo map link that one will need to manually copy and paste into a browser address bar as the BB software cuts it in half:
mapper.acme.com/?ll=37.71662,-119.64639&z=15&t=T
On the above topo, Tunnel View is off to the left, west about 1.7 miles, and is labeled, Discovery View, the old name. At the time the parking areas were full and lots of visitors were milling about. Numbers of photographers from novices with smartphones to pros with DSLRs on tripods were lined up at the rock wall of the vista point while vehicles continually played merry-go-round about parking areas. Although many were aware the rainbow would occur, most visitors there were not so were in for a surprise. If one is not a serious photographer, I would recommend viewing through a tripod mounted binocular. I installed my Sony SEL55210 telephoto zoom on my tripod mounted A6000 camera and set it to 171mm in order to include the whole fall plus some of the surrounding landscape that is a 4000 by 6000 pixel image. The below rainbow images are 33% downsized crops from some of those full images.
The rainbow in the fall mist begins to show first at the lowest point at frame left with a red color and as the sun continues to slowly lower in the sky off to the west, additional rainbow colors show at the bottom as the earlier colors move right towards the base of the fall. Once rainbow colors start rising up the fall itself above the splash zone, there is less mist so the peak mist rainbow is at that point. Most afternoons are intermittently breezy and the water falling itself tends to cause a cold mist wind flow, both of which continually change the color patterns. When a wind gust occurs, it can blow the mist around so when one sees the spray blowing about, it is time to be ready to fire off a camera shutter.
The above image occurred at 4:21pm while this next image below at 4:24pm that shows the noted progression from red to orange to yellow.
At 4:26pm I could see the start of the green color just at tree level per image below. Of the rainbow colors, green tends to be weakest.
Quickly following that blue shows below at 4:27pm and it tends to make identification of the green easier just above it.
The last color is purple and it tends to last longest. The below was at 4:32:19pm so it took about 11 minutes for all the colors to appear. At this point the red color is at the top of the splash zone mist. This is a crop from the full image at the top of my post.
Here is another shot below at 4:32:44pm that emphasizes the purples.
In a week or two will have some of the above on my 2017 Trip Chronicles page.
David
