The air was still and humidity low, there were a few clouds on the horizon, and light smog was evident. Some of my fellow Naturalists had told me that they'd been seeing green flashes lately, so it was in the back of my mind that I might see and photograph a green flash. For the first exposure, taken with a 200mm lens, I braced the camera against a wooden piling, tripped the shutter, and captured what I now know as an Omega Sun.

Sunset sequence with the "Omega Sun" that is predictive of an observable inferior-mirage flash.
Source: Andrew T. Young .

It has long been known that this type of sunset is predictive of an observable green flash.     The comparison of the Sun's shape, when inferior mirage is present, to the capital Greek letter Omega was made by the Italian astronomer Annibale Ricco` about a century ago. He was one of the first people to photograph the setting Sun at the horizon.
Source: Andrew T. Young .

After that first exposure I replaced the 200 mm with a 500 mm catadioptric (mirror) lens. The first thing that I noticed were two "bumps" (distortions) at the "ten o'clock" and "two o'clock" positions. These distortions appeared to migrate up, as the sun descended - - -