A telescope is a tool used by astronomers to look at objects far off in space. They are able to collect more light than the eye can so that we can observe faint objects in great detail.
Telescopes use curved, polished pieces of glass to collect light from objects in space. This glass can be a mirror or a lens. The light is brought to a focus point to make a clear image of the object. We call the science of moving light around using mirrors or lenses, optics.
The bigger the mirror or lens, the more light the telescope can collect. A typical amateur telescope might be 30 - 50 cm, whereas the Liverpool Telescope has a 2-metre primary mirror!
The largest ground-based optical telescopes in the world are in the 8 - 10 metre range allowing them to collect between 16 and 25 times as much light as the Liverpool Telescope. There are even bigger telescopes in space.
The first telescope was designed by Hans Lippershey in 1608. Since then, telescopes have got bigger and better! Telescopes were originally designed with eyepieces to let astronomers look through them, but nowadays professional telescopes have special instrumentation which allows the light to be detected more efficiently.