Moon With Green Rim and Cathedral of Evora

April 05, 2015


Photographer: Miguel Claro
Summary Authors: Miguel Claro; Jim Foster

The photo above shows the nearly full Moon rising juxtaposed to the Cathedral of Evora in Portugal. It was captured on January 5, 2015, using a camera attached to my 560 mm telescope. I was positioned about 1.5 mi (2.4 km) away from the cathedral. Note the green rim on the Moon's upper limb. Green rims and flashes can be seen with the unaided eye on the Sun's upper limb as it rises or sets, but because the full Moon is so dim compared to the Sun, such flashes can only be seen with magnification during moonrise or moonset. Because of atmospheric dispersion when the Sun or Moon is rising or setting, separate images of the visible spectrum colors result that cause the uppermost rim to flash green or blue if the right atmospheric conditions exist. Blues and violets (shorter wavelengths) are refracted more by the atmosphere than are oranges and reds.

Evora’s Cathedral (Portuguese: Se de Evora) is one of the oldest and most important monuments in the city of Evora. It was declared a World Heritage Site by UNESCO in 1988. Dating from the 12th century, it's the largest of the medieval cathedrals in Portugal, and one of its best examples of Gothic architecture.

Photo details: Canon 50D camera; ISO 1600; 1/10 sec. exposure; f/7 at 560mm; Astro Professional APO ED80 single exposure. Photo taken at 6:14 p.m.