Encore - Green Flash Turning Blue

January 18, 2020


Today and every Saturday Earth Science Picture of the Day invite you to rediscover favorites from the past. Saturday posts feature an EPOD that was chosen by viewers like you in our monthly Viewers' Choice polls. Join us as we look back at these intriguing and captivating images.

: Laurent Laveder
Summary Authors: Laurent Laveder; Jim Foster

April 2014 Viewer's ChoiceThis photo sequence shows a green flash (second and third photos) and blue flash (fourth and fifth photos) observed at sunset near the Mont Saint-Michel, France. The weather had been fair for several days as northwestern France was under the influence of a large anticyclone. When I noticed a mock mirage atop the Sun, I realized that the green flash might follow and was thus prepared to photograph it. If sunlight is refracted through a strong thermal gradient above the surface, a mock mirage may form. However, only when there's a marked vertical magnification of the mock image of the Sun (or in some cases multiple images) will color separation produced by differential refraction be visible to the eye or camera — green and sometimes blue colors. The five photos of this sequence were snapped in about 3 seconds. Always protect your eyes when looking toward the Sun, even when the Sun is low in the sky. Sequence taken on March 15, 2014.

Photo Details: Camera: Canon EOS 6D; Lens: 100-300mm; Focal Length: 300mm; Aperture: f/8.0; Exposure Time: 0.0031 s (1/320); ISO equiv: 800; Software: Adobe Photoshop Lightroom 5.3 (Windows).