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We use telescopes to
collect lots of light and
focus it onto detectors
using mirrors or lenses.
Large modern telescopes,
like the Keck Telescope
shown below, can collect
6,000,000 times as much
light as the human eye.
Keck Telescope
A lunar eclipse only happens around the time of a full moon, when the Sun, Earth and Moon are almost in a line (see diagram to the right). When the Moon enters the Earth's shadow, less light reaches its surface and it appears orangey-brown.
During a Partial lunar eclipse, only part of the Moon is inside this shadow, but with a Total lunar eclipse, the Moon is entirely inside the Earth's Umbra (the dark cone-shaped shadow in the picture).
Because the Earth's shadow is much larger than the Moon, lunar eclipses can last nearly 4 hours, with a total lunar eclipse (Moon in the umbra) lasting up to 1 hour 40 mins.
