Green Rim on the Moon

August 26, 2016

Lunar Green Segment On The Moon Setting Behind The Wind Mill - EPOD (2)

Photographer: Dario Giannobile
Summary Authors: Dario Giannobile; Jim Foster

The photo above shows the almost full Moon setting behind a windmill that once served the salt ponds in the foreground. It was taken at Marsala, Sicily, Italy on August 16, 2016. A green segment appeared on the Moon's upper rim just before it set. The inset at upper left shows more detail of this.
Green rims are a refraction phenomenon resulting from dispersion in the atmosphere. In essence, the setting Moon (or more likely the setting Sun) is smeared so that separate, stacked images of the rising or setting lunar disk appear for the red, yellow and green colors. Since green is the topmost color, if atmospheric conditions are right, a distinct green rim can be observed just before the Moon dips below the horizon. As it sets, sometimes a flash of green light can be detected from the upper rim.
Photo Details: Camera Model: Canon EOS 7D; Lens: EF70-200mm f/2.8L IS II USM; Focal Length: 200mm; Aperture: ƒ/2.8; Exposure Time: 0.017 s (1/60); ISO equiv: 800; Software: Adobe Photoshop CC 2015.5 (Windows).