By Iain Todd

Published: Saturday, 05 February 2022 at 12:00 am


When setting out to capture images of the night sky for the first time, most people probably start by thinking what sort of camera they need, when in fact making sure you have the right sort of telescope for astrophotography is just as important, if not more so.

Whether you’re a beginner or a seasoned astronomer, it pays to do a bit of research as to what type of telescope you’ll need to photograph the night sky.

"Take
Take time to research which sort of telescope is best for your needs. What do you want your astrophotography telescope to do? Credit: Tony Rowell / Getty Images

And as is the case with visual observing, the best astrophotography telescope for you will depend on what sort of targets you want to photograph.

You will also need to consider what you’re going to mount your telescope on, as it will need to track your object as it moves across the sky, and this is especially the case for deep-sky astrophotography where longer exposures are required.

For more on this, read our guide to telescope mounts.

Read on for our guide to everything you need to know to photograph the Moon, the planets and deep-sky objects like galaxies and nebulae, and our pick of some of the best telescopes for astrophotography.

Understanding focal ratio

"PrimaLuceLab
The PrimaLuceLab Airy APO 65F’s 420mm focal length makes it a relatively fast (f/6.5) instrument.

When choosing a telescope for astrophotography – or, indeed, for visual observing – it pays to consider the focal ratio of the instruments available.

Focal ratio (f-ratio) gives an indication of the ‘speed’ of an optical system: the time it takes your telescope to deliver a set amount of light.

As the f-ratio goes up, so the image scale increases: the object appears larger and consequently dimmer.

So f-ratio is a key value that will help you choose which telescope to use for a specific type of astronomical target.

The f-ratio is defined by dividing your telescope’s focal length by its aperture, using the same units.

So if you have a 100mm refractor with a focal length of 900mm, its f-ratio is said to be f/9.

Adding a 2x Barlow lens increases the effective focal length to 1,800mm and doubles the f-ratio to f/18, but there is a limit to how much focal length is useful.

Telescopes for photographing the Moon

"Moon
This view of the Moon was captured by John Tipping from Cheshire, UK, 16 May 2019 using a Canon EOS 700D DSLR camera and Sky-Watcher 178mm Maksutov-Cassegrain.

DSLR cameras are a great choice for photographing the Moon, and because they have detachable lenses they can be connected directly to a telescope, turning the scope into the camera lens.

This requires a T-adaptor and a T-ring. The ring mounts on your DSLR and screws into the adapter, which then attaches to your telescope.

For high-resolution lunar imaging, you may want to use a high frame rate planetary camera.

"Lunar
Avani Soares captured amazing close detail on the lunar south pole by using a C14 Edge telescope with a ZWO ASI 290 camera.

You can use any good quality telescope to photograph the Moon, but large aperture Schmidt-Cassegrains and Maksutov-Cassegrains are popular choices with lunar photographers.

Their longer focal lengths are suited to close-up imaging of the Moon, and compared to a high-quality refractor telescope you get a much larger aperture for your money.

Whatever type of telescope you use to photograph the Moon, make sure it’s well collimated if need be.

Your mount should be stable and sturdy and the ability to track the Moon with a motor drive or with a Go-To mount is a must when using a high frame rate camera.

Make sure the drives are tracking at the lunar rate, not the rate at which the stars move across the sky.

Telescopes for photographing planets

"Mars
Keith Johnson captured this image of Mars before, during and after opposition from Ferryhill, County Durham, UK between 31 August – 30 October 2020. Keith used a ZWO ASI 290MM mono camera and Celestron 9.25-inch Schmidt-Cassegrain on a Sky-Watcher EQ6 Pro mount.

You need a telescope with quite a bit of magnification to photograph surface details on your chosen planet.

To see more detail, you need to increase the magnification or image scale (how big an object appears in the image frame).

This is determined by the focal length of your telescope. As a telescope’s focal length is fixed, you might think that it can only give one magnification, but this isn’t the case.

Optical amplifiers such as a Barlow lens can effectively increase it, while focal reducers effectively lessen it.

"Saturn
Dmitry Ardashev captured this image of Saturn and its rings from Zaprudnya, Russia on 26 July 2021 using a ZWO ASI462MC camera and a TS-Optics UNC 10-inch Newtonian on a Sky-Watcher EQ6-R mount.

In terms of your telescope’s focal ratio (see above), large values make the image appear dim and require lower frame rates and longer exposures, and beyond a certain value your telescope won’t be able to deliver any more useful detail.

Under average seeing conditions, figures of f/15-f/25 will probably work best.

If you are lucky enough to experience excellent seeing, values in the f/25-f/45 range can be effective.

"The
The Moon occulting Mars, captured by Ricardo J. Vaz Tolentino, Belo Horizonte, Brazil, 6 September 2020 using an Orion StarShoot Solar System Color Imaging IV camera, Sky-Watcher Skyliner-400P FlexTube Dobsonian, Celestron Ultima 2x Barlow

A key skill when photographing the planets is knowing how to select the best image scale for the prevailing conditions.

Apertures of 8 inches or larger are best for high-resolution planetary imaging, and the ideal telescope would be a large aperture, long focal length, colour-corrected (apochromatic) refractor.

This kind of scope is great for providing the unobstructed high-contrast views necessary to reveal detail on a planet’s disc.

"Uranus
Uranus and moons Umbriel, Titania, Arial and Oberon photographed by Harvey Scoot, Essex, UK using a C14 Edge HD telescope and ZWO120MMS camera.

Reflecting telescopes can also be excellent planetary scopes, but to get high image scales you need a long focal length instrument.

As aperture increases, such an instrument can become heavy and cumbersome, making it difficult to mount and handle.

One popular design for planetary astrophotography is the catadioptric scope, which uses both mirrors and lenses.

The Schmidt-Cassegrain design balances size and performance with affordable cost.

And since the optics of this kind of scope effectively ‘fold’ the light path, a large aperture, long focal length Schmidt-Cassegrain is also fairly easy to handle.

"Saturn
Saturn photographed by John Chumack, Dayton, Ohio, USA, 20 August 2021 using a ZWO ASI224MC camera and a Celestron C11 Schmidt-Cassegrain.

You’ll also need a solid mount for planetary imaging. Ideally an equatorial design, polar aligned with driven right ascension and declination axes.

If you have a smaller telescope, don’t worry: telescopes under 8 inches in aperture are capable of capturing some detailed shots under the right conditions.

The key is to keep the image scale realistic for the size of the scope and conditions.

A family portrait of Jupiter with its four Galilean moons, for example, can be just as stunning as a close-up.

"Jupiter
Jupiter and three of its Galilean moons captured by Sona Shahani Shukla, New Delhi, India, 15 August 2021 using a ZWO ASI178MC camera and an 8-inch Sky-Watcher 200P Dobsonian.

 

Telescopes for photographing galaxies

It’s a common assumption that you need a large and powerful telescope for deep-sky imaging.

Since many deep-sky objects are rather large, smaller, short focal length telescopes with wider fields of view can be very effective, especially for regions of nebulosity that are particularly extensive.

"The
The Pinwheel Galaxy, photographed by Rouzbeh Bidishahri, Vancouver, Canada, 10 June 2021 using a QHY268M camera and Planewave CDK12.5 astrograph on an Astro-Physics 1100 GTO mount.

Although the old adage ‘there’s no substitute for aperture’ is valid for observing deep-sky objects, it’s not quite so important for imaging, as you can compensate for smaller apertures with longer exposures.

The larger the telescope, the greater the loading on the mount; the heavier the load, the more work the mount will have to do to track properly.

Longer focal lengths will also put greater demands on a mount’s tracking abilities.

"One-armed
One-armed spiral galaxy NGC4725 by Chad Leader, Shenandoah National Park, Virginia, USA, April 2021. Equipment: ZWO ASI 294MM Pro mono camera, Celestron EdgeHD 8-inch SCT, Sky-Watcher EQ6-R Pro mount

Small tracking errors are amplified by long focal lengths, so choose your telescope carefully to get the most from your system and to ensure that your mount and telescope are well matched.

If your main interest lies in galaxies and globular clusters, then their relatively small apparent size will mean that a longer focal length telescope is a good choice to photography them in detail, so consider a Schmidt-Cassegrain instrument or Newtonian reflector.

These objects do look great in a wider field of view, though, which enables you to see them in a wider setting.

Telescopes for photographing nebulae

"The
The North America Nebula by Rachael and Jonathan Wood, Doncaster, 15 June 2021. Equipment: ZWO ASI294MC Pro camera, Sky-Watcher Evostar ED80 refractor, Sky-Watcher HEQ5 Pro mount

If your interests are more nebula-based, a short focal length refractor would be a good choice for photographing nebulae. Many deep-sky imagers find a 3- or 4-inch refractor perfect for this purpose.

The advantage of using a small refractor is that it will place fewer demands on your mount, both in terms of load-bearing and tracking performance.

This is why many established imagers recommend these instruments to people starting out on the imaging road.

Can one telescope do all astrophotography?

"Crater
The Moon’s Crater Copernicus captured with a Nikon CoolPix 4500 camera attached to a 125mm Schmidt-Cassegrain on an equatorial mount. Credit: Ade Ashford

If your interests are polarised between planetary or lunar observations and deep-sky imaging, a Schmidt-Cassegrain with a focal reducer-field flattener will cover a lot of the astrophotography ground.

Armed with this knowledge, it’s time to take the plunge! But which are the best telescopes for astrophotography?

We’ve reviewed quite a lot of telescopes over the years, and below we’ve picked out some of the best astrophotography telescopes for beginners and experienced imagers alike.

Best telescopes for astrophotography

1

Celestron 114LCM computerised telescope

 

The Celestron 114LCM has a 4.5-inch mirror and a focal length of 1,000mm giving a focal ratio of f/9.

The 114LCM makes for a great planetary imager. We were able to capture a wonderful image showing Saturn and a crisp view of its majestic rings.

Turning to the Moon, we were able to undertake an 8-panel Moon mosaic showing off great detail on the lunar surface.

The 114LCM is not suited to deep-sky imaging, but is certainly one to go for if your interestes lie closer to home, within our Solar System.

It offers good optics and a computerised mount that can point straight to your chosen target with the touch of a button.

Read our full Celestron 114LCM computerised telescope review.

2

Tecnosky AG70 astrograph

 

The TecnoSky AG70 is designed to help astrophotographers capture images with as little fuss as possible, and it goes along way to fulfilling this brief.

It has an optical system designed to eliminate issues with star shapes and colour problems and removes the need to use a coma corrector.

The AG70 has a focal length of 350mm, making it great for capturing extended objects and large nebulae. A fast f/5 focal ratio allows for short exposures, which is good news for those using DSLR cameras.

Plus, considering the AG70 measures just 310mm and weighs 2kg, it’s a portable telescope, making it a good option for astrophotography sessions in far-flung sites.

Read our full Tecnosky AG70 astrograph telescope review.

3

SharpStar SCA260 Aspherical Cassegrain Astrograph

 

At over 700mm long and 280mm wide and weighing 15kg – without camera or guiding equipment – this is a serious instrument for dedicated astrophotographers, but among other similar telescopes it boasts a relatively low price tag.

Its optical arrangement makes the SCA260 suitable for a wide range of astrophotography cameras.

Using a full frame colour CMOS, we were able to capture a large target like the Pleiades in its entirety, with beautiful diffraction spikes on the brightest stars.

Turning to a smaller sensor camera we got lovely images of galaxies like NGC 891. It’s these sorts of images that first got us interested in astro imaging.

Smaller deep-sky objects like the Cigar Galaxy and the Dumbbell Nebula showed good detail and a close-up field of view.

Read our full SharpStar SCA260 Aspherical Cassegrain Astrograph review.

4

Explore Scientific ED127 apo refractor

 

"Explore
  • Buy now from B&H

The ED127’s air-spaced triplet is ideal for getting good views of faint deep-sky objects and for finer details on the planets and the Moon.

A focal length of 952mm gives it a focal ratio of f/7.5.

During our imaging run we found good consistency across a non-full frame DSLR sensor at prime focus.

The ED127 also makes for a good medium-resolution planetary imaging instrument, and we acquired some lovely detail in our lunar images when paired with a high frame rate camera.

We photographed the lunar surface at prime focus through a red, green and blue filter without re-focusing between filters.

We were impressed with the results: combining individually filtered data didn’t introduce any noticeable colour fringing.

Read our full Explore Scientific ED127 apochromat refractor review.

5

Unistellar eVscope eQuinox

 

"Unistellar