The best telescope for astrophotography beginners: refractor, Newtonian or SCT?

4 November 2026 · 5 min read

The best telescope for looking through is often the worst one for photographing with. Visual observers want aperture: the more light, the brighter the view. For deep-sky imaging, a small telescope with a short focal length and a flat field almost always gives better pictures in the first year, because it asks far less of the mount and of you.

The short answer: a 50–80 mm apochromatic refractor at 250–450 mm focal length with a built-in or matching flattener. It frames the biggest, brightest targets, needs no collimation, and works on a small mount.

What matters for imaging, and what doesn't

Focal length decides the field of view. A short focal length shows a wide piece of sky and hides small tracking errors. Most of the famous nebulae, plus Andromeda and the Pleiades, are a degree or more across, so 250–450 mm suits them. See the field of view calculator guide.

f-ratio decides how fast you collect signal. f-ratio is focal length ÷ aperture. Every halving of the f-ratio collects the same signal in about a quarter of the time. f/4–f/6 is typical for imaging scopes; f/2–f/3 astrographs are very fast but less forgiving.

A flat field decides whether the corners are usable. A simple refractor focuses light on a curved surface, so stars stretch at the edges. A field flattener (or a reducer-flattener, which also shortens the focal length) fixes that. Many imaging scopes now have one built in.

Colour correction decides whether stars have halos. "ED", "apochromatic" or "APO" refractors use special glass so blue and red come to the same focus. Cheap achromats give bloated, purple-fringed stars.

Aperture matters less than you'd think. For extended objects like nebulae, the brightness on each pixel depends on f-ratio, not aperture. A fast small scope can match a slower big one.

Weight matters more than you'd think. Everything you add has to fit within your mount's imaging limit. See mount payload.

Small apochromatic refractors

The default first imaging telescope, and for good reason.

• Good: sharp, flat, no collimation, cools to the night air in minutes, light enough for small mounts and trackers.
• Less good: small aperture per dollar, and most galaxies stay small at these focal lengths.
• Look for: a built-in flattener or a matching one from the same maker, a published back focus, an image circle big enough for your sensor, and a solid focuser.
• Examples: William Optics RedCat 51, Askar SQA55 and FRA400, Sharpstar 61EDPH III, and many similar 50–80 mm astrographs.

Newtonian astrographs

Short, fast reflectors built for cameras, often with a coma corrector included.

• Good: the most aperture and speed for the money. No colour fringing at all.
• Less good: needs collimation (aligning the mirrors), sometimes every session. The open tube catches wind and dew, and bright stars get diffraction spikes from the secondary's supports.
• Look for: a model sold as an "astrograph" or "imaging Newtonian" with a focuser strong enough to hold a camera, and a matching coma corrector.

Schmidt-Cassegrains and other long scopes

Compact, long focal-length telescopes, superb for planets and small galaxies.

• Good: long focal length in a short tube. Galaxies, planetary nebulae and planets.
• Less good: very hard as a first imaging scope. The field is tiny, tracking errors and seeing are magnified, guiding through an off-axis guider is close to essential, and focus shifts as the mirror moves. Most SCTs also need a reducer for imaging.
• The exception: the Celestron RASA is a Schmidt design at f/2 with a short focal length, made only for cameras. Very fast, but heavy and demanding about tilt and back focus.

Telescopes to avoid for a first imaging rig

• Dobsonians. Their mounts don't track the sky the right way for long exposures, and many can't reach focus with a camera.
• Department-store reflectors and long achromats. Wobbly mounts, poor focusers and coloured stars.
• A big telescope on a small mount. The mount always loses.
• Anything without a published back focus. You'll be guessing at spacers.

Comparison

Matching the telescope to your camera

Once you have a shortlist, check three numbers against the camera:

1. Image circle against sensor size. APS-C needs about 28 mm of well-corrected field; full frame about 44 mm.
2. Back focus against your imaging train, often 55 mm. See back focus.
3. Image scale against your seeing: 206.265 × pixel size ÷ focal length. See image scale and sampling.

The rig builder does all three as soon as you pick a telescope and camera, and How to build an astrophotography rig explains the rest of the chain.

Questions

Is a bigger telescope better for astrophotography? Not for a first rig. A small, fast, flat-field telescope gives better results sooner, because it asks less of your mount, your polar alignment and the sky.

Can I use a camera lens instead? Yes. A good 135 mm or 200 mm prime lens on a star tracker is one of the best ways to start. See the best beginner setup.

What focal length should my first telescope be? 250–450 mm. It frames most of the best-known nebulae and the largest galaxies, and it's forgiving to track.

Do I need an apochromat? For colour cameras, an ED or apochromatic refractor is strongly recommended. Narrowband imaging with a mono camera is more tolerant of colour error.