Telescope glossary

Aperture: Diameter of the primary mirror or lens, which allows a telescope to collect light.
Field of view: Area of sky visible through the eyepiece.
Focal length: A telescope’s tube length. Short focal lengths offer a wide field of view and a small image.
Focal ratio: Also known as the telescope’s speed. Small focal ratios provide lower magnifications, wide field of view and a brighter image.
Magnification: Relationship between the telescope’s optical system and the eyepiece. 

For the uninitiated, choosing a beginners’ telescope can be a confusing affair — especially when you’re bombarded with jargon. is here to make the search simpler for you.

First, a little primer on telescopes. Simply put, these instruments are categorized into two major optical kinds: reflectors and refractors. Reflectors, or reflecting telescopes, use an internal primary and smaller, secondary mirror to focus the light into the eyepiece in order to create an image. Meanwhile, refractors, or refracting telescopes, make use of lenses to focus the light into the eyepiece. In other words, reflectors reflect light, while refractors tend to bend — or refract — it. Some instruments make the most of mirrors and lenses, they’re known as Maksutov-Cassegrains, Schmidt-Cassegrains or catadioptric telescopes