Fogbow, Glory and Brocken Spectre Observed from Viterbo Airport

October 25, 2018


Photographer: Marco Meniero
Summary Authors: Marco Meniero; Jim Foster

Shown above is a photo of a fogbow, glory and Brocken spectre as viewed from Viterbo Airport in Rome. Most often seen in mountainous terrain (or airplanes) when clouds are below the level of the observer I was able to view this optical phenomenon from the 100 ft level (30 m) of the airport's air traffic control tower. The Sun was directly behind the camera.

Fogbows are devoid of color because the tiny droplets that compose fog (about 0.5 mm in diameter) allow individual spectral colors to overlap. Note that rainbow and fogbows are portions of a circle. At ground level the horizon blocks out approximately 1/2 of this circle, but when the horizon is below eye level, as in this case, a circular bow will result. Diffraction processes and not refraction and reflection are primarily responsible for the formation of the glory and Brocken spectre, seen at the center of the fogbow. Photo taken on September 15, 2018.

Photo Details: Canon EOS 5DMk3 camera; and Sigma 20 f/71.4 lens; 8 photos used.