First colour photograph of the green flash
Vatican Observatory
first first
Italy ()

The green flash is a rare atmospheric phenomenon that occurs immediately after sunset or just before sunrise. Essentially it is a mirage of the Sun, in which the highly refracted sunlight produces a green spot at the top of the Sun. The effect is best seen in stable atmospheric conditions in which the observer has a clear unobstructed view of the horizon. The first colour photographic proof of this elusive phenomenon was taken by DKJ O’Connell of the Vatican Observatory, Italy, in 1960.

The green flash only ever lasts a second or two, just as the Sun breaches the horizon.