Brightness of a Total Lunar Eclipse

“Looking at the pictures of the progression of a lunar eclipse, the Moon turns red, but there’s no apparent change of brightness of the Moon as it progresses from full moon to total eclipse. Therefore, a total lunar eclipse cannot be the result of the Earth casting its shadow on the surface of the Moon.”

Some flat-Earthers —presumably never seen a total lunar eclipse in person before— actually claim that.

There are in fact changes in brightness of the Moon as a lunar eclipse progresses. It can be easily observed if we see it in person. And it is very apparent, the Moon becomes noticeably darker as it progresses from a full moon to a total eclipse.

In a series of pictures showing the progression of a lunar eclipse, the moon appears to be in constant brightness as it progresses from full moon to total eclipse. The reason is that the camera is set up to compensate for the drop in brightness by increasing exposure. This is why the resulting pictures appears to be in similar brightness.

In reality, the difference in exposure between a full moon and a total lunar eclipse can be as much as 19 stops. In other words, a full moon can emit 500000× more light than in total lunar eclipse.

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