A long focal length folded into a short tube
A catadioptric telescope uses a mirror and a correcting lens together, and folds the light path so that a long focal length fits inside a short tube. A Schmidt-Cassegrain or a Maksutov of two metres of focal length is barely longer than an arm, which is why these are the tubes that travel and the tubes that sit on a balcony. The long focal length makes them natural planetary and lunar instruments: high magnification comes from ordinary eyepieces rather than from extreme ones. Three properties come with the folding. Cool-down is the first and the most often ignored — a closed tube with a thick corrector holds the warmth of the house, and the image will not settle until the glass has reached the outside temperature. The second is the corrector plate itself, which faces the sky and collects dew before anything else on the instrument does. The third is back focus: the focuser works by moving the primary mirror, so the distance behind the tube where an image forms is generous, and it is what makes these tubes so adaptable to cameras, reducers and diagonals. Read which of the two designs is in front of you — a Maksutov usually carries a smaller obstruction and a slower ratio, a Schmidt-Cassegrain a larger aperture for the money. We compare aperture, folded focal length and ratio, corrector design, obstruction, back focus, cool-down guidance, tube weight and mount supplied.
80 mm Maksutov · T-2 thread and dovetail
A compact 80 mm Maksutov with a coated front lens, a T-2 thread with buffer ring, a finder shoe and a GP dovetail that fits photo tripods and standard mounts.
Best for: A travel optic that doubles as a long lens on a photo tripod
≈ €166
100 mm aperture · 1400 mm focal length
A 100/1400 Maksutov on an EQ3 equatorial mount with slow-motion controls on both axes, supplied with a 25 mm Plössl, an erecting prism and a phone holder.
Best for: A compact planetary telescope that also works on landscapes
≈ £341 / €336
127 mm Maksutov · 1500 mm focal length
A 127/1500 Maksutov-Cassegrain on the AZ-GTi Wi-Fi GoTo mount, controlled from a phone rather than a handset.
Best for: Lunar, planetary and double-star observing from a small or awkward site
≈ £649 / €784
8-inch Schmidt-Cassegrain · computerised GoTo fork
An eight-inch Schmidt-Cassegrain on a single-arm computerised fork mount, with a 40 000-object database and the maker’s SkyAlign alignment routine.
Best for: An observer who wants serious aperture that still fits in a car boot
≈ $1499 / £1500 / €1537
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