My Favourite Astro Lens
- Scotia Astro
- Mar 8
- 7 min read
Today we’re taking a look at my favourite astrophotography lens, the mighty Samyang 135 F2.
I wanted to share my thoughts today on a fantastic lens for astrophotography that can be used on traditional DSLRs or dedicated astro cameras. This isn’t a new lens, but I use it in a slightly different way compared to some astrophotographers. I thought you might like to see how I pair it with this custom rig.
I use other great lenses for my astrophotography projects, like the Samyang 14mm F2.8, 85mm F1.4, and the Sigma 24mm F1.4. However, for wide-field, deep-sky targets, the 135 is hard to beat! I’ve been really impressed with the quality of my Samyang lenses and my copies have all been mechanically excellent and tack sharp.
The Samyang, also known as Rokinon in some parts of the world, is a fast 135mm F2 lens. It is compatible with a wide range of camera mounts, including Canon, Sony, and Nikon. I use a Canon EF compatible version, as its the best fit on my dedicated astro cameras.
Physical Specifications
In terms of physical specs, the Samyang 135 weighs in at around 800 grams and is just under 15cm long. It’s a manual focus lens, but don’t let that put you off, as being able to focus manually is a great benefit, especially in astrophotography, where precise focus is crucial for clear images.
The aperture range of the lens goes from F2, right up to F22, but for astrophotography purposes, I would never really venture above F4. For the vast majority of my images, I’ll stick to F2 or F2.8.
The lens is actually made up of 11 separate lenses in seven groups, some of which contain ED glass elements or extra low dispersion. This is particularly useful in maximising light transmission and providing great colour correction and minimising chromatic aberrations, which can really affect faster lenses. You can find ED glass in other high end astro products including telescopes and binoculars, so its great to see it included for this lens too.
One of the best features of the lens though is the price! This is a complete steal, especially given the quality of astro images you can get out of this lens. You can grab the Samyang 135 f2 here in the UK for under £500.00 and I’ll list the price in some other countries here too.
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A subtle, but very important feature when its comes to astrophotography is the lens hood. You’ll see here that it’s totally flat at the top. What’s the big deal with that…Who cares? Well, Astrophotographers do, especially when it comes to taking your flat calibration frames. I typically use an LED light panel and on the Samyang’s lens hood, it sits flush and means no light spillage. Good flat frames are essential in post processing and they remove dust spots and vignetting from your images, so this lens hood is a real saviour.
A Wide-field Wonder
Shooting at 135mm is so much fun, especially for big and bright nebulae and other larger galaxies like Andromeda. I love the framing options that you have at this focal length and when you bring the fast F2 focal ratio of the Samyang into play, its really a winning combination.
By shooting at fast ratios of F2 and F2.8, the Samyang can capture a great amount of detail, even in shorter imaging sessions. I call it my mini RASA! By pairing the lens with a dedicated astro camera, you can tease out even more details. Let’s have a look now at some of the cameras that I use with this lens.
My Camera Choices
Depending on my target and how I want to frame it, I switch between my two One Shot Colour dedicated astro cameras, both from ZWO.
The 2600MC Pro sports a 26MP APS-C sensor and gives wider views of many targets. Thanks to its high end features, like its low read noise, two stage cooling and no amp glow, the 2600 gives consistently stunning views. When paired with the Samyang 135, the images are sharp and captured in high resolution.
I also use the smaller, but no less impressive 533MC Pro. Like its bigger brother, the 533 can be cooled, to help with noise control and its eliminates amp glow in sub exposures. These are really handy features to have in a camera, as they increase the quality of your sub exposures and this really helps when it comes to stacking and post processing. I also like the fact that its smaller 9MP sensor is square shaped, which is really fun when framing certain targets with the Samyang 135.
Connecting the Samyang 135 to these cameras is really easy, thanks to some custom fittings from ZWO. I use their handy filter drawer attachment, as I usually image with broadband and narrowband 2 inch filters, depending on my target.
This filter drawer has an integrated Canon EF mounting, so its a perfect fit with my Canon compatible Samyang lens. It’s also made at the ideal width to help in achieving the required back-focus for this imaging train.
Back-focus can be a frustrating business at times, but with this configuration, its pretty straightforward. There’s also a helpful guide to connecting Canon lenses to this filter drawer on ZWO’s website, which I’ll link to here, so go check that out for more information. By having the filter drawer attached this way, its super easy to swap filters in and out.
For narrowband targets, like emission nebulae, I’ll generally use my Optolong L-eXtreme, or more recently, an IDAS NBZ UHS filter. Many emission nebulae are rich in Hydrogen Alpha and Oxygen 3 and the L-eXtreme and IDAS NBZ targets these emissions lines at specific band passes.
If I want to capture a target in broadband with more natural colours, like galaxies, I’ll swap in a light pollution filter, like the IDAS LPS D2. In some cases, if the conditions allow and there’s no moon, I’ll image without a filter.
My Use Cases
So how do I currently use the Samyang 135?
Well, as you can see here, I’ve custom fitted my lens to this cool 3D printed ring system, which I picked up from First Light Optics here in UK, but its made by a great company in Canada, called Astrodymium.
This is the second iteration of this build though and I started off with a much simpler, but less integrated model, before switching.
When using my Samyang 135 with my dedicated astro cameras, I clamped the camera in a ZWO holder ring and then attached the camera. This did work perfectly fine and meant I was still free to add the integrated filter drawer, but for focus I was using the manual ring on the lens. I did I short video on it last year, so go check that out if you want to see how I connecting everything.
As time went on, I really wanted to add an auto focus solution, so that led me to the much better Astrodymium system.
This new ring system is specifically made for the Samyang 135 and all of the components fit together perfectly. You can grab this is in a variety of specifications, but I got the full system with brackets and mounts for the ZWO EAF and an ASIAIR.
As I usually have limited imaging time, due to our lovely Scottish weather, I need rigs that are fast and efficient to image with and this outfit really helps with that. So let’s take a closer look.
The main feature of this system is obviously the Samyang 135 itself and its mounted in a sturdy pair of rings. On top of the rings, there’s a handy guide-scope rail, which I sometimes use to mount my ASIAIR, if I’m not guiding. There’s also a side plate specifically for the ASIAIR, but I find it easier to pop it in and out of the guide-scope rail.
I can easily change the aperture of the lens without taking to out of the rings, so this is a major time saver. I’m also able to secure my dew strip around the lens, with no issues. One tip here is to try and get a thinner dew strip. I was previously using some pretty chunky ones, which work great, but in this configuration, its tricky getting them to fit properly.
I picked up this fantastic replacement from Move Shoot Move and it’s been a great performer. Its thinner profile means I can slot it in the ring system no problem and it also has some power control, so you don’t need to have it blasting at full whack when you don’t need to.
On the other side of the rings, there’s a housing for a ZWO EAF, which is really the secret sauce of this rig. The manual focus ring on the lens itself is great and has perfect tension to it, but there’s no real comparison between manually focussing and using the EAF. This is especially true when it comes to focus shifting, which can occur when temperatures fluctuate throughout the night. The EAF can be set to refocus when this happens, so it’s a great addition to have.
The autofocus works via a timing belt and pulley system and this was really easy to fit, thanks to the comprehensive and clear instructions from Astrodymium. They’ve really done a great job on this product, so nice job folks!
You can get an additional Vixen style dovetail bar to fix to the bottom of the rings, but I prefer the beefier Losmandy plates…which can be overkill for a system like this, but its rock solid with no flexing and ultra stable.
The Samyang and its ring system sits nice and snug in the Losmandy clamp on my Skywatcher AZ-EQ6 GT mount here and this pairing has never let me down during an imaging session.
The ring system also helps with cable management, as I can keep all the components close together, making for a much wider rig. Dangling cables can really mess with your guiding and sometimes throw your rig off balance, so it’s good to keep everything as tidy as possible.
So that’s my overview of my favourite astrophotography lens and feel free to check out some of the images that I've taken with it in the gallery here, or on my Social Media channels.
Hope you can join me again for another astrophotography blog from here in the UK. Take care of yourselves, be well and clear skies to you all!
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