The color of the moon at totality in a lunar eclipse varies. It isn't always the color of blood, so calling every lunar eclipse a "blood Moon" is far from accurate. Atmospheric conditions on Earth determine the color that we'll see. For example, volcanic ash in the air makes for a dark Moon. Scientists measure the appearance and brightness of a total lunar eclipse using the five-point Danjon scale - ranging from 0 to 4.

The scale was devised by French astronomer Andre-Louis Danjon.

Mona Evans
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