What is a lunar eclipse?

A lunar eclipse occurs when Earth comes between the Sun and the Moon and (part of) the Moon is shaded by Earth. Lunar eclipses can be seen by anybody on Earth for whom the Moon is above the horizon, and are therefore much more common than solar eclipses. They take place up to five times a year and totality can last up to 100 minutes.

When the Sun, Earth and Moon are well aligned, the Moon is completely covered by Earth’s full central shadow – at these times we see a total lunar eclipse. Some sunlight is refracted onto the Moon through Earth’s atmosphere, giving the Moon a reddish colour.

When the Moon is less perfectly aligned with Earth and the Sun, the full shadow may cover only part of the Moon’s surface – at these times we see a partial lunar eclipse.

When the alignment is even less perfect, the Moon falls within the more diffuse partial shadow cast by Earth. The resulting slight shading of the Moon’s surface is much more subtle and difficult to observe.

Discover more about eclipses here.