One of the most important characteristics of a telescope is its objective diameter, which is referred to as its aperture. The larger the aperture a telescope has, the ‘faster’ it is.

The naked eye has a light-gathering power that can just make out stars and other astronomical objects down to the 6th magnitude. Anything fainter cannot usually be seen. Most objects in the sky are fainter than this, so you need a telescope with an appropriate aperture as a ‘light amplifier’.

A telescope with a 100mm aperture can image much fainter stars and deep sky objects. Under really dark skies, this size of telescope can see stars that are a 1000 times fainter than the naked eye alone.

A telescope with a 200mm aperture can image stars 3900 times fainter than the faintest which can be seen with the naked eye alone.

Newton telescope with 200mm aperture

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Newton telescope 114mm aperture