What types of telescopes are there to choose from?
There are three basic types or designs of telescopes. (a) Refractors: these use a large objective lens as their primary light-collecting element. With this design, the viewer looks straight through the full length of telescope, observing from the back, rear or opposite end of the unit from the objective lens. The refractor delivers superb resolution, contrast and image quality but becomes very expensive as the aperture increases. (b) Reflectors: these designs, the most common being the Newtonian type reflector, use a concave primary mirror to collect light. The light is reflected by a small, flat secondary mirror to the side of the main tube for viewing. With this design, the viewer observes objects by looking into the side of the tube near the objective (opening). The reflector delivers the best overall value with regard to light-gathering power, especially in large aperture designs. (c) Catadioptric or Combination Mirror/Lens Telescopes: typically known as Schmidt-Cassegrains or Maks
