july: earth's shadow

Lunar eclipses, such as that seen is some parts of the world this month, differ from solar eclipses is several ways. One of the most obvious is that the Moon does not generally become totally dark. Light is refracted through the Earth's atmosphere into the cone of darkness. What colour the Moon appears will depend on the dust, gas and clouds currently in Earth's atmosphere, and can be assessed using the Danjon scale.

This image combines three photographs taken at the beginning, middle and end of an eclipse, as the Moon passes through the Earth's shadow. The light areas at the extreme left and right show the edges of the shadow cone. Notice how the shadow becomes progressively darker towards it centre, at the top of the image.

Image: Stephen Barnes.