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How do telescopes work?

A modern astronomical telescopeA modern astronomical telescopeA telescope is an instrument that makes distant things appear closer. It enables us to see details that are not visible with the naked eye. Binoculars are made up of two telescopes, one for each eye. Astronomers use powerful telescopes to study objects in space. They are specially designed to collect as much light as possible. Images from these telescopes reveal details of the Moon, planets, nebulae (clouds of dust or gas) and galaxies that we cannot see simply by looking up at the night sky.

A diagram of a large reflecting telescopeA diagram of a large reflecting telescope


Modern telescopes used by astronomers are called reflecting telescopes. They use mirrors to collect light coming from distant objects and form an image. The image can be viewed with an eyepiece, or it falls on a light sensor in a digital camera and can be viewed on a computer screen. Astronomers can view the images sent over the internet from a telescope located in another part of the world.

Image of a galaxy seen through a powerful telescopeImage of a galaxy seen through a powerful telescope

The Hubble Space Telescope is so sensitive it could detect light from a torch 400,000 kilometres (250,000 miles) away.

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