toptics
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Highlights
Mahdi Zamani (site, InstG) captured this scene a few hours before the lunar eclipse of July �19.
On Easter Island, Rapa Nui, a Moai gazes impassively as a cloud torn corona wraps the Moon.
Image ©Mahdi Zamani, shown with permission
A Mie calculation of a corona made by IRIS. There is a bright central aureole surrounded by rings of rapidly decreasing intensity.
The corona is irregular. Distant parts dissolve into disordered cloud iridescence.
Coronae and iridescence are the same physical phenomenon. Tiny cloud droplets diffract moonlight.
Below: Parallel light rays from the left reach a water drop. They scatter from points all over its surface and leave as outgoing spherical waves. that's the diffraction bit.
The waves overlap and interfere. Cones of bright light form where the overlap is constructive. The cones from millions of drops give a corona in the sky.
