My annual Yosemite moonbow workshop starts Thursday, and if Mother Nature cooperates (and Congress can get its act together enough to keep our National Parks funded), everyone in my group should have something like this by the end of the workshop.
Given the right conditions, photographing the Yosemite Falls moonbow isn’t rocket science. These conditions–ample flow in the fall, a full moon at the correct angle, and (fingers crossed) clear skies–align most reliably each spring, a fact not lost on the general public. Unlike the February Horsetail Fall spectacle, the Yosemite Falls moonbow attracts as many awestruck observers as serious photographers. Most end up the bridge at the base of Lower Yosemite Fall, where I captured the above image. This is the closest location to view the moonbow, but the crowds and heavy mist here make photography difficult. I usually start my groups here at the lower fall, but I also take them to other less crowded vantage points as well (but if I shared them here, they would no longer be less crowded, would they?) .
Under ideal conditions the moonbow at the Lower Yosemite Fall bridge is bright enough to appear to the naked eye as a shimmering silver band. But even the brightest moonlight isn’t enough to allow the human eye to register the moonbow’s color. With its ability to accumulate light, a camera can reveal the moonlight’s entire spectrum. Advantage camera.
Even when you can’t see a moonbow–because, for example, you’re too far away or the moonlight is reduced by thin clouds– your camera can still bring it out with a long enough exposure, if you know where to position yourself. With the moon low on the horizon (less than 38 degrees), your shadow (cast by the light of the full moon) will point to the center of the moonbow (the apex of its arc)–the lower the moon, the greater its arc. (This approach also works if you’re trying to photograph an “invisible” moonbow in falling rain.)
To capture this image I stood on a bench and shot over the top of about one hundred heads, praying for 30 consecutive seconds without mist or a (totally useless) flash from one of many point-and-shoot cameras. I couldn’t resist going vertical and wide (17mm) to include the Big Dipper, which was perfectly positioned to appear as if it is Yosemite Falls’ source. Experience has given me the “go-to” full moon settings I used here: ISO 400, f4, 30 seconds.