Unintentional double exposure

Perhaps the most intriguing pictures to come out of this photo workshop in Arizona are bats drinking on the wing in total darkness. Because the Sonoran desert is so dry, the artificial pond on this private property draws the bats all night long. The shot you see here is an unintentional double exposure. During the 30 second exposures, if more than one bat breaks the electric beam, the flash units fire multiple times. In this instance, two long eared myotis bats used a similar flight path to drink. Fortunately, they were positioned perfectly. Had they taken the same flight path, they would be superimposed over each other from the camera's point of view and I would have trashed the shot. I used f/22, 1250 ISO, flash white balance, and a locking cable release that forced the camera to continuously take 30 second exposures until the battery was depleted. My group and I had retired to our hotel once the cameras were set up and we tested the focus and exposures. So, I was asleep when this photograph was taken!