How do you evaluate a total lunar eclipse?

The Danjon Scale is used to evaluate a total lunar eclipse. (Image credit: NASA/JPL)

Danjon Scale of Lunar Eclipse Brightness

The French astronomer André-Louis Danjon proposed a useful five-point scale for evaluating the visual appearance and brightness of the moon during total lunar eclipses. The L values for various luminosities are defined as follows:

L = 0: A very dark eclipse. The moon is almost invisible, especially at mid-totality.

When L = 0, the moon is almost invisible in the sky. (Image credit: NASA/JPL)

L = 1: A dark eclipse with gray or brownish coloration. Details are distinguishable only with difficulty.

When L = 1, the moon appears gray or brown in the sky. (Image credit: NASA/JPL)

L = 2: A deep red or rust-colored eclipse, with a very dark central shadow, while the outer edge of the umbra is relatively bright.

When L = 2, the moon appears deep red or rust-colored in the sky. (Image credit: NASA/JPL)

L = 3: A brick-red eclipse, with the umbral shadow usually having a bright or yellow rim.

When L = 3, the moon appears brick-red in the sky. (Image credit: NASA/JPL)

L = 4: A very bright copper-red or orange eclipse, with the umbral shadow having a bluish, very bright rim.

When L = 4, the moon appears copper-red or orange in the sky. (Image credit: NASA/JPL)

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