Lunar Corona Over the Chesapeake Bay

April 29, 2007


Provided and copyright by: Rob Bruner, NOAA
Summary author: Rob Bruner

The photo above showing a lunar corona over the Chesapeake Bay of Virginia was taken close to midnight on December 6, 2006. A corona, also called a lunar diffraction ring, occurs when the light from the Moon (or Sun) is obscured by the water droplets or ice crystals that make up the thin clouds (altocumulus or altostratus) passing between the Moon and the viewer. Light waves are deflected or bent by tiny water droplets, having a nearly uniform size, around the obstruction, forming usually pale concentric rings. Blue is observed on the inside and red (rust) on the outer ring. Smaller drops result in larger diffraction angles and a larger corona, as shown above.

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