The elusive green flash

The green flash is a very small green light that appears to be emanating from the top of the sun just as it sinks below an absolutely clear horizon. It lasts only a second or two. For years I thought that watching for the green flash was a kind of hazing ritual like sending a new Boy Scout on his first camping trip in search of a “left-handed bacon stretcher.” It turns out that the green flash is real.  It is caused by a combination of the prism-like refraction of light by the atmosphere and the mirage effect caused by atmospheric temperature gradients, like the visual distortions seen over a hot roadway in summer. In my nearly 70 years, I have seen the green flash only a few times despite years of looking for it, and I have never successfully caught a photograph.  Apparently airline pilots see it regularly.  My sister who lives in a coastal town in southern California has seen it many times. I think my problem is that I have been looking for it off the Oregon coast where an absolutely clear horizon at sunset is very rare.  Even on a seemingly cloudless summer day, clouds suddenly appear out to sea as sunset approaches.

Last fall on a particularly beautiful and clear day, I set up my camera with a telephoto lens on a tripod and clicked photos every second from just before to just after sunset. In the first photo below, you can see what is called a green rim on the top of the sun.  This is caused by refraction and can be seen commonly using a telescope.  Sometimes you can also see a red rim on the bottom, but that is not evident in this photo.  The green rim cannot be seen with the naked eye.

In the second photo, the image of the sun is distorted by the mirage effect making it look like it truly is entering the sea. At first I thought I might have captured a green flash above the setting sun, but I’m pretty sure it is just a cloud.

In the final photo, there is just a sliver of sun still showing.  This might be the moment that a green flash would appear, but alas, no luck on this day.