Every amateur telescope is one of three things, and knowing which one you are looking at explains most of its price, its size and its quirks. This page is the map: what each design is, what it costs, and what it is for.
Refractors, lens at the front
Light passes through an objective lens. Sealed, maintenance free, high contrast per millimetre, and the most expensive way to buy aperture. Small ones are excellent grab and go instruments; large apochromats are photographic tools. The cheapest apochromat in this index prints $498.00.
Reflectors, mirror at the back
Light bounces off a primary mirror. The cheapest aperture available, which is why nearly all large amateur telescopes are reflectors. Needs occasional collimation and has an open tube. The dobsonian is a reflector on a simple mount and is the value champion of the shelf, printing $305.00 for 130mm here.
Catadioptrics, both together
Mirrors plus a corrector lens, folding a long focal length into a short tube. Compact, popular on computerised mounts, longer cool down. The schmidt cassegrain and the maksutov are the two you will meet, and they suit observers who want tracking and portability more than raw aperture.
Questions people ask about telescope
What are the types of telescopes?
Refractors using a lens, reflectors using a mirror, and catadioptrics using both. Every amateur instrument is one of the three.
Which type of telescope is best?
For value and faint objects, a reflector. For portability and low maintenance, a refractor. For tracking in a small package, a catadioptric. None is best at everything.
What is the difference between telescope types?
How they gather light. That one difference sets the price per millimetre of aperture, the length of the tube, the maintenance and, largely, what the instrument is good at.