Green Flash from Frankfurt, Germany

April 19, 2005


Provided and copyright by: Ditmar K. Hutmacher
Summary authors & editors: Ditmar K. Hutmacher; Jim Foster

The sequence above showing a green flash on the upper rim of the Sun was taken near Frankfurt, Germany. From time to time, I use a foot and bicycle path adjacent to the Main River to watch the setting Sun. On this day (March 10, 2005), the air was very clear, and I was indeed pleased to be able to observe and shoot this green flash segment -- a few seconds later, another "flash" was visible. The flash above had a distinct green hue but on this photo appears more gold than emerald in color.

The green flash is a refraction phenomenon that results because of dispersion in the atmosphere, which "smears" the setting Sun in such a way that a separate "image" appears for the red color, yellow color and the green color as well. The rims of these "images" are stacked with the green rim on top and the red on the bottom. If conditions are right, once the red and yellow rims slip below the horizon, the uppermost green rim then sets with a discernable flash. However, the actual green flash is about ten times smaller than the naked eye can see.What we basically see is an anomalous refraction -- a mirage.

It's easier to see the "flash" over water than on land, and you're likely to have more success with binoculars or with a camera having a telephoto lens than with the unaided eye. In addition, it seems to help if the setting Sun appears more yellow in color rather than red. This photo sequence was captured using Nikon Coolpix (12 x 45) binoculars and a steady hand -- no mount or tripod was used. Use utmost care in looking toward the Sun with binoculars, a telescope or the unaided eye. See also the Earth Science Picture of the Day for March 11, 2004.

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