This photo of the green flash at sunset was the Astronomy Photo of the Day for 2014-06-04
Here is a video of the green flash observed from Italy on 2021-10-16 which was Astronomy Photo of the Day for 2021-11-10.
I have seen the green flash twice, both while I lived on the California coast and had an unobstructed view of the Pacific to the west. I tried many times to photograph it but never even observed it when I had the camera set up to try to capture it. Today, you’d just set up a video camera and record every sunset until you caught one, but in the age of film still photography it was a much more difficult undertaking.