How does a telescope work?

A larger telescope mirror (or lens) collects more light and reveals fainter objects. It also produces a sharper image, showing more detail. Magnification – determined by the focal length of the eyepiece – is less important.

For telescopes, bigger is better. A larger telescope aperture means a brighter and sharper image: the bigger the primary lens or mirror of a telescope is, the fainter the stars it can detect and the finer the detail it reveals. In astronomy, magnification is not so important: by using an eyepiece with a long focal length, a telescope’s magnification can be increased significantly, but the resulting image is fainter and the resolution – the amount of detail – does not get any better. Seen through a telescope, planets or galaxies look bigger than with the naked eye: the image is spread out over a larger part of your retina or the camera detector.

Have you ever looked through a telescope? What you see depends on the telescope’s objective and eyepiece. You can try it here. Choose your target and explore!