Telescopes | Astronomy | Cosmos

Explaining the Different Parts of a Telescope

A telescope is a precision instrument, made up of several distinct working parts. The principle is simple – by collecting, magnifying and redirecting light, the telescope produces a close-up image of whatever it is pointed at. Each individual piece of a telescope has to be manufactured and assembled exactly according to specification for the scope to work correctly, a process that takes considerable care, skill and attention to get right.

Telescopes work by gathering optical light and focusing it through a lens, prism, or mirror. These optical elements either curve (refract) or reflect the light into a focal point, allowing the human eye (or a computer, or a camera) to produce an exact image of the original light source.

The main part of any telescope is the lens, a curved sheet of glass that is manufactured with a perfect axial symmetry and is used to bend or refract rays of light. Multiple lenses may be included in a single telescope to reduce the presence of optical aberrations – inaccuracies in the image produced by the curves in the lens itself. In a refracting telescope, there are normally two convex lenses positioned at opposite ends of the scope. The largest lens, found at the front of the scope, is known as the ‘objective lens’, and determines the amount of light allowed into the scope. The larger the lens, the more light is allowed, but the larger the scope has to be.

Reflective or catadioptric telescopes also feature a series of curved mirrors that act instead of, or in conjunction with, the objective lens to produce a crisper image that isn’t affected by optical aberrations. Usually found in so-called ‘light-bucket’ telescopes, reflecting telescopes allow for much larger objective lenses than refractors.

The tube is normally cylindrical, and ground completely smooth in order to facilitate perfect transference of light from the lens to the eyepiece. It is also the protective casing that keeps the fragile internal components from breaking and damage.

The eyepiece is a cylindrical attachment, either to the back of the telescope (in a refractor) or to the top (reflector or catadioptric) that focuses the light collected by the objective lens or reflective mirrors into the final image seen by the human eye.

The mount is used to support and stabilize the telescope. Mounts come in two styles- altazimuth or equatorial. Altazimuth mounts are freely able to move along the vertical or horizontal axes, allowing them to be moved easily as needed. Equatorial mounts need to be aligned along the Earth’s axes of rotation, but are much more stable and precise. Also, equatorial mounts can be fitted with drive motors to turn them in place.

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