If you’re getting started in deep-sky astrophotography, I believe that a compact apochromatic (APO) refractor telescope is the best possible choice.
A compact APO refractor is portable and lightweight, making it a smoother transition from the camera lenses you may be used to. In fact, in many ways, a high-quality apochromat is very much like a telephoto lens.
If you’re interested in photographing nebulae and large galaxies in the night sky through a telescope, this article should shed some light on the decision-making process ahead of you.
In 2020 I worked with Radian Telescopes to develop my own signature refractor telescope, the Radian 61 APO. This triplet apochromatic refractor has a wide focal length of 250mm, and an f-ratio of F/4.5.
The Andromeda Galaxy. Radian 61 APO + Canon EOS Ra.
This is a lightweight telescope that can be used on a star tracker, yet is future-proofed for upgrades such as mounting an autoguiding system, or even an electronic focuser.
The attention to detail and “turnkey’ nature of this package (includes rings, dedicated corrector, dovetail) is the perfect choice for anyone transitioning from a camera lens to their first telescope.
Throughout the past 8 years of deep-sky astrophotography, I’ve made lots of mistakes. In the beginning stages, I made critical errors in selecting and setting up equipment.
From the beginning, my goal was to capture deep-sky images of nebulae and galaxies. This type of astrophotography requires the most advanced equipment and demands a careful setup routine.
The type of telescope you choose early on can have a dramatic impact on the complexity of your deep-sky astrophotography setup. In my experience, a compact, wide-field refractor offers an improved user experience over the other telescope types during the acquisition stages of astrophotography.
For example, I began taking my first deep-space images with a reflector telescope. If I could go back and I do it all over again, I would have chosen a compact, wide-field refractor to start astrophotography with.
These days, I use a refractor telescope for 90% of my astrophotography.
I am not saying that there is anything wrong with starting your astrophotography journey with a Schmidt-Cassegrain Telescope (SCT) or Newtonian Reflector, but I believe you will have some additional challenges to overcome early on.
No matter what type of photography experience you have going in, deep-sky astrophotography through a telescope will have a number of challenges to overcome early on.
This includes understanding how to polar align an equatorial mount, how to focus your camera on a faint deep-sky object, and how to attach your camera to the telescope. two out of the three challenges become more difficult if you’re not using a wide-field refractor to start.
The statement above is not theoretical, I personally experienced these frustrating moments in my backyard years ago. I should have started with a compact refractor telescope.
A recent photo of NGC 7822 captured using a color camera and a 100mm refractor.
I Should Have Started with a Refractor
I often see newcomers to deep-sky astrophotography starting with a telescope that will make an already challenging hobby even more difficult. I went through this experience personally, and this is what happened.
My first astrophotography telescope was a Meade LXD55 6″ Schmidt-Newtonian. I purchased this reflector telescope from a local camera store second-hand, for a great price.
At the time, I had very little knowledge of telescope types, optical designs, or astronomy in general. I took the advice of the salesman at the store, and he assured me that “this telescope can be used for astrophotography”.
The telescope I started taking pictures of space with.
First off, he was right. It could certainly be used for astrophotography, and I even found astrophotography images online taken by others using this particular model.
The problem was, this type of telescope presented some pretty daunting challenges to overcome. My long-term love for astrophotography was at stake, as a poor experience could potentially sour me on this new adventure.
Thankfully, I kept a positive mindset throughout the process despite having limited knowledge (and limited funds).
This was my First Astrophotography Telescope
My first telescope for Astrophotography was NOT a refractor, and it presented some challenges.
I mounted the Meade LXD55 SN6 to a Celestron CG-5 (Advanced Series GT) computerized telescope mount. The GoTo tracking mount was my biggest investment in the hobby early on, and looking back the mount was performed surprisingly well.
A Schmidt-Newtonian is a promising instrument for astro-imagers. The corrector plate helps you collect images with less coma than a traditional reflector design.
Essentially it’s a catadioptric telescope that combines elements from both the Schmidt camera and the Newtonian reflector. A spherical primary mirror is combined with a Schmidt corrector plate to correct the image.
It looks capable enough in the picture, so what’s wrong with starting your astrophotography adventure with a Newtonian Reflector, Schmidt-Cassegrain, or a Ritchey–Chrétien?
Some would argue that there is nothing wrong with any of these choices, but here’s why it wasn’t a good fit for me:
It was Heavy and Difficult to Balance
It wasn’t a bad telescope, and I even managed to collect my first-ever deep-sky image with it. I really had no idea what I was doing at this point, and was absolutely thrilled to finally captured a tracked deep-sky object in the night sky.
The problem with this old Meade telescope was that it was not a great type of telescope to start with. Looking back, a compact refractor telescope would have made my life a lot easier at the time.
For starters, it was rather heavy and difficult to balance. It was at the maximum payload capacity of my equatorial mount (Celestron CG-5), and I even had to use some “custom” counterweights to achieve balance.
In the astrophotography world, you never want to have your telescope rig reach the weight limits of your telescope mount. This puts extra stress on the equatorial drive system and often results in poor tracking.
My first picture of M31 (Andromeda) using the Meade reflector telescope (July 2011).
It Had Too Much Magnification
In my opinion, the telescope had a little too much focal length as well. Extra magnification can be great for pulling in small targets, but it’s also more demanding on aspects such as pointing accuracy, tracking, and focus.
Prime-focus astrophotography involves attaching your camera directly to the focuser of the telescope, with no additional eyepieces or lenses between them. That means that the native focal length of the telescope decides the field-of-view (FOV) and scale of the objects you shoot.
The SC6 had a focal length of approximately 762mm, which could be considered to be a “mid-range” focal length. For comparison, my William Optics Zenithstar 73 refractor has a focal length of 430mm.
I really shouldn’t complain about the 762mm focal length (FL) of the 6″ Meade, some amateur astrophotographers start out with an 8″ SCT with a demanding 2000mm+ FL. (I think I would have given up!)
The Focuser was Loose and Difficult to Secure
As newcomers will tell you, achieving a tight focus on your deep-sky subject can be challenging early on (Here are some tips). It’s hard enough to find the optimal focus distance without worrying about the focuser “slipping” out of position on its own.
Like a traditional Newtonian telescope, the focuser is placed near the front of the optical tube to collect light from the secondary mirror. This creates a challenging situation in terms of balance, especially when using a heavy, full-frame DSLR camera.
The weight of my camera would put stress on the objective end of the optical tube. Despite using the locking screw, the DSLR would eventually fall downwards into the focuser as the night progressed. I constantly had to re-adjust focus after 4-5 images.
In general, I find reflector telescopes to be more challenging to focus than a refractor, and that was certainly the case with this F/5 Schmidt-Newt.
Start with a Compact, Wide-field Refractor
I’m not saying that a refractor telescope is the only way to go, but I think you’ll find that the astrophotography community generally agrees with me on this one. To be more specific, an apochromatic refractor is best.
Refracting telescopes use lenses, not a mirror, to deliver crisp views through the eyepiece, and high contrast, well-corrected color images with your camera.
In late 2011, early 2012, I invested in an Explore Scientific ED80 Triplet APO refractor. The reason I call this an “investment” is that not only did this telescope reward with me with my best images to date, but quality glass hold their value quite well.
Below, is an old photo of my 80mm refractor telescope on a Celestron CG-5 equatorial telescope mount. The difference between the images I was collecting with the Schmidt-Newt and the APO refractor was night and day.
The stars were small and well-corrected (all of the colors came to a focus at once), and I no longer dealt with coma, reflections, and dramatic vignetting.
My first refractor telescope was an Explore Scientific ED80.
Another advantage this telescope had was the field of view. Being a beginner, I had my heart set on capturing some of the most iconic deep-sky objects like the Orion Nebula, Andromeda Galaxy, and the Pleiades star cluster.
The focal length of this telescope (480mm) was a perfect fit for all of these targets. I didn’t need to worry about creating a mosaic to fit the entire object in the frame. Images like this were the reason I got into astrophotography in the first place.
Finding targets in the night sky became a lot easier thanks to the forgivingly wide field of view. Even if the pointing accuracy of my computerized equatorial telescope mount was off, I could usually find my intended deep-sky target within the field-of-view of my first slew.
See my list of recommended refractors for astrophotography.
The first summer (2012) with my Explore Scientific 80mm refractor telescope was an exciting one. I captured several amazing photos of deep-sky objects with my Canon EOS Rebel Xsi DSLR.
The most exhilarating photo came in July of 2012 when I attempted to photograph the Andromeda Galaxy with my 80mm refractor and stock Canon DSLR. The image was a monumental improvement over my attempt the previous summer. I was especially thrilled at the clarity of the image and natural star colors recorded.
My first successful image of the Andromeda Galaxy (July, 2012).
The Perfect Astrophotography Telescope
A high-quality doublet or triplet apochromatic refractor is capable of producing sharp, flat, well-corrected images. Almost all types of telescopes are capable of impressive astrophotography images, but some make you work a lot harder for it.
For example, a Newtonian Reflector presents an advantageous light-gathering ability and an affordable price-per-aperture. However, Newtonians require regular collimation and adjustments to avoid coma and perform at their best.
An apochromatic refractor will perform much better in terms of photography than its less expensive achromat counterpart.
The objective lens (consisting of 2 or more pieces of glass) of an apochromatic refractor is designed to focus light to the same point, and correct chromatic aberration. As you can see in the diagram below, an apochromatic objective focuses different wavelengths of light closer to the same point than an achromat does.
“The strict definition of apochromatism is having three wavelengths of light focusing to the same point. This normally requires a third lens element in the objective. The normal configuration is a positive, low-dispersion crown, combined with two high-dispersion flints, one negative and one positive. The lenses can be cemented, air-spaced, or a combination thereof.” Starizona.
For a technical description of how a refractor telescope works, and the refractive index of certain mediums, check out this informative article.
Pros and Cons of a Compact APO Refractor Telescope
There are some pros and cons to using a compact refractor telescope for astrophotography, and here they are:
- You can mount them to modest, entry-level equatorial mounts
- Refractors are compact and lightweight compared to other telescope designs
- The focusers are solid and easy to focus
- They offer a similar experience to a high-end telephoto camera lens
- The image quality potential for astrophotography is exceptional
- Refractors do not require regular collimation or optical adjustments
- They offer a forgiving, wide field-of-view
You can mount a small refractor on a portable tracking mount like the Sky-Watcher Star Adventurer.
- They are the most expensive telescope type (price per aperture)
- They are not well-suited for high-magnification planetary imaging
- The apertures are often too small to observe faint deep sky objects
- Galaxies and smaller DSO’s need 1000mm+ for an up-close view
My favorite astrophotos of all time were all taken using a refractor telescope. From my first experiences with the Explore Scientific ED80 to the massive Sky-Watcher Esprit 150 Super APO, refractors are my number one choice for astrophotography.
The image below shows a William Optics Zenithstar 73 refractor mounted to a modest Sky-Watcher HEQ5 GoTo telescope mount. My DSLR camera is attached to the focuser of the telescope for deep-sky imaging at 430mm.
This entire ensemble can be lifted up and moved around the yard on a moment’s notice, so I usually keep the entire imaging system ready to go in the garage.
A setup like this is also refreshingly easy to travel with. It does not take up very much space in my vehicle and can be re-assembled quickly.
A portable deep-sky imaging setup with a 73mm refractor telescope.
This versatile and reliable rig does not come at the expense of performance either. A small setup like this is capable of producing incredible astrophotography images using a DSLR/Mirrorless camera or a dedicated astronomy camera.
The photo below shows the image captured using the telescope setup pictured above in my video titled “Taking a Picture of the Andromeda Galaxy“.
This image includes 67 x 120-second exposures using a Canon EOS 60Da.
My latest version of the Andromeda Galaxy using a DSLR and a small refractor telescope.
My Newtonian Reflector Collects Dust
In 2014, I decided to purchase an 8″ Newtonian Reflection, the Orion 8″ F/3.9 Astrograph Reflector. The idea was to add some light gathering power and a little more focal length at an affordable price.
However, I had become used to the quick and setup time of my 80mm refractor, and balancing the big optical tube on my Sky-Watcher HEQ5 mount was time-consuming.
Also, I had to regularly collimate the tube before each and every imaging session. Perhaps the telescope was perfectly collimated before I attached my camera, but I always had to make sure before spending a night collecting images.
I did manage to capture some impressive images with this setup, but surprisingly, the added aperture did not add the extra “punch” to my images I was looking for. In the end, this telescope was a lot more effort, for very little (if any) benefit to my astrophotography.
I do not use my 8″ Newtonian Reflector very much these days.
What Size and Brand Should You Buy?
I’ve used refractor telescopes with an aperture of 51mm, all the way up to 150mm. Smaller, compact APO’s are much more practical and affordable, yet do not sacrifice as much performance as you may think.
For example, the image of the Lagoon Nebula and Trifid Nebula region of Sagittarius was captured with a miniature (51mm aperture) William Optics RedCat APO and a DSLR camera. This quadruplet refractor weighs just 3.2 pounds and can fit in your carry-on bag.
Nebulae in Sagittarius using a William Optics RedCat 51 APO.
Nearly every telescope manufacturer builds refractor telescopes, and I’ve had the opportunity to try many of them. I’ve had wonderful experiences using apochromatic refractors from Explore Scientific, William Optics, Meade, and Sky-Watcher.
William Optics compact doublets are very popular and rather affordable considering the optics used in their designs. The Zenithstar 73 APO is one such example, and a telescope I have personally taken a lot of beautiful images with.
The Sky-Watcher Esprit line of refractors is a step up, with the Esprit 100 Super APO (Triplet) being my most used refractor of all time. These telescopes are expensive and quickly grow in price as aperture is added.
Setting up the Sky-Watcher Esprit 100 refractor telescope in the backyard.
When choosing a refractor telescope for astrophotography, ensure that it is an apochromatic optical design, not an achromat. Also, ensure that the optical tube includes a robust, 10-1 speed focuser that can lock into position when needed.
You’ll also need to confirm that the mounting hardware will allow you to mount the telescope to your equatorial mount, and add additional accessories such as a guide scope and camera for autoguiding.
Make sure you invest in the appropriate field flattener for your refractor, as this extra glass lens will help flatten the field of view to the very edges of your picture.
If your astrophotography interests lie in taking images of nebulae and large galaxies, an apochromatic refractor should be your number one choice of telescope.
This category of deep-sky objects includes some of the most iconic wonders in space, and you could spend a lifetime capturing them.
Not only is an APO refractor a perfect fit in terms of focal length (native magnification), but the images with your DSLR/Mirrorless or dedicated astronomy camera will be extremely sharp and well-corrected.
If you’re looking to photograph the planets, a compact refractor is not for you. Smaller targets such as planets and many galaxies are not a good fit for a wide-field refractor.
But if you’re a fan of quick set up time, consistent results, and wide-field nebulae like the ones below, you simply cannot beat an APO refractor.
The Soul Nebula in Cassiopeia using a William Optics Zenithstar 73 APO.
The Soul Nebula in Cassiopeia using a William Optics RedCat 51 APO.
Recommended Refractors for Astrophotography
The following list of apochromatic refractor telescopes have all produced exceptional results for me personally, so I feel comfortable recommending them. They are all compact, wide-field instruments capable of producing images like the ones shared in this post.
- Explore Scientific ED80 Triplet APO F/6 (FCD 100)
- William Optics Zenithstar 73 F/5.9 Doublet APO (FPL-53)
- Sky-Watcher Esprit 80 F/5 Super APO Triplet (FPL-53)
- Meade 70mm F/5 Astrograph Quadruplet APO (FPL-53)
- William Optics RedCat 51 F/4.9 (or SpaceCat) (FPL-53 + FPL-51)