Encore - Moonrise with Green Rim

June 13, 2015

EPOD_EncoreMoonrise with Green Rim

Take a look back at some of the EPODs our viewers found particularly eye-catching. Today, and every Saturday EPOD invites 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.


Photographer: Chris Kotsiopoulos
Summary Author: Chris Kotsiopoulos; Jim Foster

The photo above shows a glorious full Moon on the rise, looking like the Sun, as viewed from the Temple of Poseidon at Sounio, Greece. I was positioned approximately 1.25 mi (2,000 m) to the southwest of the Temple as this golden Moon eased above the eastern horizon. A close inspection along the top edge of the Moon reveals a tinge of green. At moonrise, and more frequently at sunset, a sharp-eyed observer can sometimes detect a ray of pure green light atop the lunar rim -- magnification is usually needed. Green flashes and or rims occur as a result of vertical dispersion in the atmosphere. The amount of atmospheric refraction is wavelength dependent, so the blue image of the rising Moon is slightly higher than the green and red images. Each is just one arc minute displaced from a non-dispersed image. As the Moon rises (or Sun sets), the green image briefly comes into view before giving way to the red image. Of course, green flashes can be seen at sunrise or moonset as well. Photo taken on April 28, 2010 at 8:39 p.m.
Photo details: Canon Xti camera; ISO 200; 1/2 second exposure; SW ED 80.