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Telescope designs: refractor, reflector and catadioptric

Every telescope belongs to one of a few optical families. These guides explain each design, what it is best on, and how it shapes your eyepiece choice.

How many telescope designs are there?

Amateur telescopes fall into three families: refractors that use a lens, reflectors that use mirrors (chiefly the Newtonian and its Dobsonian mounting), and catadioptrics that combine a corrector lens with mirrors (the Schmidt-Cassegrain and Maksutov-Cassegrain). Each trades cost, size, maintenance and best target differently.

Which design should I choose?

It depends on what you want to observe and how much you can carry. Refractors and Maksutovs give crisp, low-maintenance planet and Moon views; Newtonians and Dobsonians give the most aperture for deep-sky objects; Schmidt-Cassegrains are a compact all-rounder. The design guides here compare them in detail.

Does the design change how eyepieces work?

No. Whatever the design, magnification is the telescope's focal length divided by the eyepiece's focal length. The design sets the focal ratio and the field on offer, not the formula, so the Fit My Telescope tool works the same for any of them.

How do the designs compare on cost and upkeep?

Refractors cost the most per millimetre of aperture but need almost no maintenance. Newtonians and Dobsonians give the most aperture for the money but need occasional mirror alignment, called collimation. Schmidt-Cassegrains and Maksutovs sit in between: their sealed tubes hold alignment well and stay clean, though they take longer to cool to the night air. The design guides linked below go through each of these trade-offs in full so you can weigh cost, size, upkeep and best target against how you plan to observe.

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Sources: Wikipedia (CC BY-SA) · Wikidata (CC0)