Omega Moon Over Cape Elizabeth, Maine

February 11, 2013

Etruscan-vase moonrise composite 012713_(6) (2)

Photographer: John Stetson
Summary Authors: John Stetson; Jim Foster

The photo sequence above shows a distorted and fiery moonrise over Two Lights State Park, Cape Elizabeth, Maine. I couldn't help but notice the Moon's inverted image (inferior mirage) as it rose on the evening of January 27, 2013 -- one day past the full Moon. As the Moon ascended slightly higher, its inverted image disappeared. Refraction in the lower atmosphere, due to a steep temperature gradient with height, was responsible for this distortion, referred to as the Etruscan vase or Omega effect. When the Moon emerged over the horizon, its inferior mirage appeared below and seemed to reach up to grab the Moon, producing the omega shape. If you look very closely you can detect a green rim on the top of the Moon (green flash), especially on the third and sixth image in the sequence.