Equipment review: Samyang 135mm f/2 (Manual Focus) — My Go-To Wide-Field Astro Lens

 First visit to this astronomy/astrophotography blog? Well, firstly a warm welcome to you and thanks for stopping by. If you want to find out more about me and this blog, why not visit my introductory page at https://undersouthwestskies.blogspot.com/2025/01/welcome-to-my-new-astronomyastrophotogr.html  You can also browse other posts by using the search bar or the blog post list on the right hand side and I'd really like to hear from you via the comment boxes. Drop me a tip, an observation or a question. Take care and clear skies to you.  Steve 

Samyang 135mm f/2 (Manual Focus) — My Go-To Wide-Field Astro Lens

If you love photographing the night sky but don’t want to remortgage your house to do it, then the Samyang 135mm f/2 could be your new favourite piece of glass. I like to keep my setup simple, reliable, and travel-friendly and I’ve been using this lens for more than two years, teamed with my Canon 800D; it’s my go-to companion for wide-field astrophotography whether it be to frame a nebula or sweep across the Milky way without lugging a telescope around.  

After two years of late nights, frosty fingers, and countless star fields, I thought it was time to share my thoughts. What makes this lens such a hit among astrophotographers? How does it perform? What are its strengths and pitfalls? And, what are the trade-offs you should know before you buy? Let’s find out.

In this review, I’ll:

• Walk through the key features
• Highlight the strengths
• Weigh up the downsides
• And wrap up with my honest verdict

My lightweight, portable wide-field astro rig incorporating the samyang 135mm f/2 lens with my canon 800D DSLR 

Overview

The Samyang 135mm f/2 is a bit of a cult classic in astrophotography circles — a manual-focus, full-frame compatible prime lens that delivers serious optical performance without burning a hole in your wallet. It’s available in several mounts (Canon EF, Nikon F, Sony E, and more), and photographers often praise it for its sharpness and contrast at a surprisingly modest price.

Think of it as the astrophotography world’s version of a dependable old telescope — it doesn’t boast flashy electronics or fancy features, but what it does offer is clarity, consistency, and a ton of light-gathering power.

At f/2, it’s a light vacuum, pulling in photons like a cosmic magnet. Even at f/2.8, stars in the corners remain crisp and clean, with minimal chromatic aberration or distortion. For me, it’s become a workhorse lens that simply delivers, night after night.

Why It Shines for Astrophotography

Here’s what I think makes the Samyang 135mm such a gem for capturing the night sky:

1. A fast f/2 aperture — a real light bucket.
Speed is everything in astrophotography. The faster the lens, the less time you need to collect light — and that means fewer tracking errors, shorter subs, and sharper stars.

2. Excellent corner-to-corner sharpness.
Even wide open, stars stay tight and well-defined all the way to the edges. Many lenses struggle with soft or warped corners, but this one keeps its composure beautifully.

3. Great value for money.
Compared to astrographs or premium telescopes with similar optical performance, the Samyang 135mm is an absolute bargain. You get premium-level sharpness at a fraction of the price — ideal for beginners or anyone building a portable setup.

4. Manual focus — an advantage, not a drawback.
In astrophotography, autofocus is about as useful as sunglasses at midnight. Manual focus gives you full control, and with a simple Bahtinov mask (you can easily 3D-print or order one online), you can achieve razor-sharp stars every time.

5. Plenty of compatible accessories.
This lens is a tinkerer's dream. You can attach support rings, dovetails, red-dot finders, guide scopes, ASIAir units — even a ZWO EAF focuser if you want to automate your setup. These can be 3D printed – if you are lucky enough to own one – or easily purchased off various shopping websites

6. Perfectly balanced focal length.
At 135mm, you’re right in that sweet spot between wide-field and close-up imaging. Large nebulae, Milky Way segments, star fields — it handles them all beautifully. On crop-sensor cameras, the extra reach (around 200mm equivalent) makes it even more versatile.

7. Impressively low chromatic aberration.
Colour fringing on stars is minimal — a big win if you’re after clean, natural-looking results, especially in narrowband imaging.

8. Portable and travel-friendly.
Pair it with a small star tracker like the Sky-Watcher Star Adventurer, and you’ve got a grab-and-go setup that can fit in a backpack. No observatory required — just clear skies and a bit of patience.

9. When using a cooled astro camera (mono/colour) with filter wheel etc, the Samyang 135mm f/2 can serve as a fast, relatively “short‐telescope” field of view—great for large nebulae, wide star fields, Milky Way segments in narrowband or broadband. Because many astro-cameras have large sensors, the good corner performance is very useful.

copyright astropical space

Disadvantages (a.k.a. “The Fine Print”)

No lens is perfect — and the Samyang 135mm does have a few quirks worth knowing. Think of these not as deal-breakers, but as “lessons from the field.”

1. Vignetting at wide apertures.
At f/2, corners can lose up to 40% brightness. It’s nothing a good set of flat frames (or stopping down to f/2.8) can’t fix, but it’s worth planning for.

2. Sample variation.
Quality control can be hit or miss. Some copies are pin-sharp, others have slight decentring or coma issues. Buy from a reputable dealer with a solid return policy.

3. Infinity focus quirks.
When used with astro cameras and adaptors, the lens doesn’t always hit true infinity focus right at the mark (particularly when using M42/T2 adapters, it seems). You may need to experiment a little with spacers or back-focus distance.

4. No weather sealing or stabilisation.
Not a huge issue for astrophotography, but if you’re shooting on cold or damp nights, dew control is essential. A lens heater or dew strap is your friend here.

5. Focusing precision required.
At f/2, the depth of field is razor-thin. Even a hair off perfect focus can soften your stars. Take your time, use Live View zoom, or better yet — a Bahtinov mask.

6. Middle-ground focal length.
Some users find 135mm to be neither wide enough for sweeping Milky Way shots nor long enough for small galaxies. Personally, I find it a perfect “in-between” — but it depends on your targets.

7. Back-focus spacing issues (for astro cameras).
When used with filter drawers or adaptors, incorrect spacing can throw off sharpness or infinity focus. It’s worth double-checking your measurements — the devil really is in the millimetres.

8. Heavier than you’d expect.
At first glance, it looks compact, but it’s got a bit of heft to it. Still, when you balance it properly on a tracker, it’s more than manageable.

My Verdict

After two years of use, I can confidently say, that based on personal experiences, the Samyang 135mm f/2 must be one of the best bang-for-your-buck astrophotography lenses out there. It’s sharp, fast, and remarkably capable for its price. A compelling option for beginners on a limited budget who want a relatively fast, high-quality lens.

Sure, it asks for a little patience — careful focusing, calibration flats, and the occasional bit of back-focus tinkering. But if you’re willing to put in that small effort, it rewards you with breathtaking wide-field images.

Copyright Stellar Discovery 

To summarise:

• Highly recommended if you’re using a DSLR or mirrorless camera and are ready to get serious about wide-field astrophotography.
• Excellent for astro-camera users, provided you dial in your adapter spacing and calibration.
• Less ideal if you need autofocus, weather sealing, or prefer ultra-wide or ultra-long focal lengths.

In short, this lens is like an honest, hard-working friend — it doesn’t boast, but it consistently delivers. It’s built for those who value results over bells and whistles.

What about you? Have you used the Samyang 135mm f/2 in your setup? What camera have you paired it with — and what celestial wonders have you captured? I’d love to hear your experiences in the comments below.

Until next time — clear skies, steady mounts, and may your focus always hit infinity.

— Steve

If you are seeking a more detailed review of the lens then try this one  - I take no responsibility for the website or any links from it - but I did find it an informative review - https://stellardiscovery.com/samyang-135mm-f-2-widefield-astrophotography/

Beginner tutorial – how to stack comet images in Deep Sky Stacker (my work flow)

First visit to this astronomy/astrophotography blog? Well, firstly a warm welcome to you and thanks for stopping by. After reading this post, if you want to find out more about me and this blog, why not visit my introductory page at https://undersouthwestskies.blogspot.com/2025/01/welcome-to-my-new-astronomyastrophotogr.html  You can also browse other posts by using the search bar or the blog post list on the right hand side and I'd really like to hear from you via the comment boxes. Drop me a tip, an observation or a question. Take care and clear skies to you.  Steve 

 Beginner tutorial – how to stack comet images in Deep Sky Stacker (my work flow)

Ever wondered how to turn your series of faint comet frames into one crisp, detailed image? In today’s post. I’ll walk you through my step-by-step work flow for stacking comet images in Deep Sky Stacker DSS) – a free, powerful tool that’s perfect for astrophotographers who want to capture the beauty of a comet without those distracting star trails.  

In summary, the work flow order goes like this:

1.      Open picture frames

2.      Then for each image use the green comet image to select the comet’s nucleus – saving the position for every frame

3.      Entering the stacking settings, choosing a comet stacking mode (Comet only, stars only, both)

4.      Starting the process of stacking

 

So, let’s dive straight into the more detailed work-flow.

Step 1: Register all images 

First, let’s get your light frames ready.

• Open Deep Sky Stacker and click ‘open picture files’
• Select all the comet frames you want to stack
• (Select all the bias, flats and dark frames you want to add in)
• Click ‘check all’ – and then choose ‘Register checked pictures’

·       In the pop-up window, make sure to:  –

o   check ‘register already registered pictures’

o   check ‘automatic detection of hot pixels’

o   DO NOT check ‘stack after registering’.

o   Then click ‘OK’ to start the registration process

This last step makes sure DSS knows exactly how to align and handle your images before we move on to the comet itself.

 

Step 2: Mark the comet’s nucleus in each image 

Now for the fun part — telling DSS where your comet is in each shot.

• Select the first image in your list
• Click the green comet icon on the right side of the screen
• hold down the Shift key and click directly on the comet's nucleus to mark its position. A pink circle should appear around it.
• Save the changes for that image. You can click ‘save all’ so DSS keeps track of the comet position across all selected frames OR
• Repeat this process for every light frame

This step can be a little repetitive, but it’s essential — it tells DSS how the comet moves across your frames, allowing it to align the comet while still handling the star background correctly.

Tip: If you’ve seen the tutorial “How to Stack and Process Comet Images with Deep Sky Stacker,” it shows a great visual example of this process. How to Stack and Process Comet Images with Deep Sky Stacker

 

Step 3: Stack the images

With everything marked, it  is time to stack your comet.

• Click ‘Stack checked pictures’.
• When dialogue box appears, choose ‘Stacking parameters’ appears
• go to the Comet tab and choose your desired stacking mode.
• "Stars" (comet trails)
• "Comet" (star trails) or
• "Stars + Comet" (both) – my go to choice  
• Click OK to start the stacking process. 
• If another pop-up window appears called ‘stacking steps’, keep the default settings and just click ‘OK’ again.

When DSS finishes, save your stacked image as a TIFF file, ready to edit in your favourite processing software — whether that’s Photoshop, Affinity Photo, PixInsight, or any other astrophotography editor.

Want to See It in Action?

If you prefer to follow along visually, these videos do a fantastic job of demonstrating how to select and use the comet stacking modes in DSS:

How to STACK Comet in Deep Sky Stacker - Beginners Astrophotography Tutorial

How to Stack Comet Images Without Star Trails in DeepSkyStacker

Final Thoughts

Stacking comet images in DSS might feel a bit technical at first, but once you’ve done it a couple of times, it becomes second nature. The reward is absolutely worth it — a clean, vibrant image that beautifully captures the motion and structure of your comet, without losing the stars in the background.

Give it a try with your next comet data set and watch your images transform! As always, if you have a tip or an observation about my work-flow, then drop me a comment so we can improve it for all and, it goes without saying, but I will anyway – stay safe, have fun and clear skies to you all

Steve

Whats happening in the night sky this month? November 2025

 First visit to this astronomy/astrophotography blog? Well, firstly a warm welcome to you and thanks for stopping by. After reading this post, if you want to find out more about me and this blog, why not visit my introductory page at https://undersouthwestskies.blogspot.com/2025/01/welcome-to-my-new-astronomyastrophotogr.html  You can also browse other posts by using the search bar or the blog post list on the right hand side and I'd really like to hear from you via the comment boxes. Drop me a tip, an observation or a question. Take care and clear skies to you.  Steve 

What’s happening in the Sky – November 2025

Date	Astronomy visual observing	Astrophotography
1/11	The Moon rising or waxing gibbous near Saturn is a nice sight south-west after dark. (Mag+0.4 Saturn 5.7 degrees from moon)  Mercury low in south-west skies.
2
3
4	Calisto's shadow transits Jupiter from 0701 to 1036. Jupiter rises 2055 - 2225
5	Full ‘Beaver’ Moon / “Supermoon”
6	6-10 Nov Early evening: check for the Pleiades cluster in Taurus (just above right of a low Moon maybe) and larger star fields; morning twilight: Venus rising low. Also - transit of Titan across Saturn 2033 - 0233 on 7/11
7	Ganymede eclipsed by Jupiter's shadow 0400
8		Comet 24p/Schaumasse crosses M44 Beehive cluster - capture with big apertures/bigger imaging rigs
9
10	71% waxing gibbous moon close to Jupiter 0600 as awn twilight brightens - both less that 4 degrees apart
11	Meteor showers: Taurids peaking. 60% moon near M44 Beehive Cluster. Saturn's tilt less than 0.5 degree - appearing virtually edge on till 8/12
12	With the last ¼ Moon waning and dark skies improving: Meteor activity (Taurids) may be seen after midnight.	go for faint constellations, try spotting the Milky Way band rising in north-east dark skies.
13		As moon subsides – good DSO’s for next twelve days include M45 Pleiades. M42 Orion,  M27 Dumbell nebula,
14	Titan occulted by Saturn 1848; reappearing 0035 on 15/11. Moon enters glancing partial eclipse by Saturn's shadow at 0125	Double Cluster (NGC 869 & 884) in Perseus – use narrowband filter; M33 Triangulum Galaxy
15	Saturn’s tilt apparent and it will continue reducing its tilt towards December
16
17	Leonids peaking. Radiant located in head of Leo the Lion, marked by sickle part of asterism. meteors around 15 per hour
18	Peak Leonids meteor shower around 17-18—best after midnight, look away from the Moon and horizon.	Dark skies good for deep sky for the next part of the month.Target the fainter DSO’s
19
20	Venus low in morning twilight; Saturn in evening; other planets may be visible with binoculars. New moon	Good 135mm targets for nights either side of new moon – IC1805 Heart nebula; NGC 1499 California Nebula;  NGC 13333 Molecular cloud reflection nebula (try long broadband filtered exposures)
21	21-25 Nov The evening sky centres on the richer winter constellations: Orion, Taurus, Gemini rising. Use binoculars/telescope to scan for clusters and nebulae. Uranus at opposition. Jupiter - 0105 - 0450 double shadow transit by Io and Callista's shadows
22	Titan transits Saturn 1852 - 0110 on 23/11
23
24
25	Shadow of Ganymede transits Jupiter 0208 – 0525. Actual moon transit between 0609 - 0929
26
27
28	1st ¼ moon
29	Saturn sits 28 Degrees s of 65% lit waxing gibbous moon
30	Titan occulted by Saturn 1722 - 2308

 

Imaging session: Chasing Comet Lemmon - A night on the Moors

  New to this blog, then welcome, and after reading this post why not stop off here and find out more https://undersouthwestskies.blogspot.com/2025/01/welcome-to-my-new-astronomyastrophotogr.html

To photograph Comet Lemmon under bright moonlight, which was the plan for this imaging session, I intend to use short exposures combined with image stacking and processing software. The bright moonlight (a waxing gibbous moon around 80% illuminated tonight) will wash out fainter details, so I’ll need to compensate with equipment and post-processing. Whilst the weather will be dry for a change, it will be predominantly cloudy with strong breezes and some big old gusts. All the apps are predicting a chance of a clear spell window between 7 – 8pm.

So, in today’s blog post, I

·       Share the story setting of the night

·       Outline how I set up for the shoot

·       List the equipment I used

·       Share the camera settings that worked on the night

In a follow up post, I will share what steps I took to stack and post edit the images collected

As always, if you have any questions, thoughts, tips or photos to share, just drop me a comment in the box at the end of the post.

Let’s dive right in then.

Chasing Comet Lemmon – A Night on the Moors

The wind has teeth tonight.
I’m high on the moors, parked in a puddled, muddy car park, off the Princetown Road — Lowery Cross, a lonely outpost overlooking the dark sweep of the Tamar Valley far below. Out on the horizon, Bodmin Moor rises like a sleeping giant under a blanket of low cloud, Cornwall’s heart beating faintly in the distance.

The sun has long slipped below the edge of the world, and the sky is in that magical in-between — half night, half memory of day. I arrived 90 minutes or so ago to survey the scene and select my final shooting position. I need a really clear view of the western sky just above the horizon and inconveniently high gorse bushes made it tricky to get that perfect view. Now, the stars above are beginning to blink awake, timid at first, then boldly twinkling between ragged ribbons of cloud that scuttle across the heavens.

Behind me, the pine forest whispers and groans, the wind threading through it like a restless spirit. When the gusts rise, it sounds like distant surf rolling on a Cornish beach — a phantom ocean that exists only in the imagination.

And then the moon climbs.
An 80% waxing gibbous — bright, brooding, and otherworldly. Its light spills across the landscape, silvering the grass and turning the granite boulders into glittering relics, each one flecked with mica that winks like frost under torchlight. The clouds become ghost-ships, drifting through a lunar sea, haloed by a faint, perfect circle of spectral rainbow

Off in the Tamar Valley, fireworks ignite the night — a carnival of colour blooming briefly in the darkness. Their echoes roll across the hills like the distant rumble of battle; scarlet, emerald, and gold flares light up the undersides of the clouds. Even the TV masts at Princetown and Kit Hill join the show, their red beacons pulsing like cosmic heartbeats. Below, the headlights of cars carve through the bends of the Princetown road — glowing orbs on a rollercoaster, swooping and diving through the moorland gloom.

Up close, my world is smaller — intimate, ritualistic. The soft, rhythmic clicking of the camera shutter keeps time with the night. The Primus stove hisses nearby, its blue flame bright and defiant against the chill, heating water that bubbles and steams into the cold air. A mug of tea warms my hands, and Fox’s chocolate cookies — a personal tradition — taste better than any banquet could up here.

Tonight’s quarry is fleeting: Comet Lemmon, shy and sinking lower toward the horizon with each passing night. My weather apps promised me one last hour of clear sky around seven — a narrow window, a final chance.  I’m fervently praying I have my calculations right – the moon should be around 50 degrees plus from the comet position.

And so here I am. Binoculars in hand, dipping in and out of the shelter provided by the raised boot hatch, to scan for Arcturus, my ‘lead in’ star for the night. Equipment has been set up on a grassy bank, tripod kept low to stop it vibrating in the wind. Polar alignment finally done; Polaris proved evasive in the small cloud gaps! The ASI air Mini is up and running, shooting details programmed in. The lens is focused – x10 live view and a bahtinov mask.

And suddenly clear skies to the west – the promised gap! I can’t see the comet due to moonlight, by Sy Safari confirms its rough location. My rig is rotated and tilted to focus on a spot in the sky. A test image of 30”. And magically just like, a faint white streak appears on the green home screen of the ASIair app. Comet Lemmon. Gotcher!

Equipment used tonight

Portability, simplicity and quick set-up time is the order of the night given the conditions and constraints. So, I opted for:

• Astro-modded canon 800D DSLR
• Wide-aperture lens – my Samyang 135mm f/2.0 to let in maximum light.
• Benbo Carbon Fibre Sturdy tripod
• Skywatcher Star Adventurer 2i star tracker (essential) - to track the movement of the sky and prevent star/comet trails in individual shots.
• William Optics equatorial wedge
• ASIair Mini – for plate solving the sky ahead of me
• Intervalometer - to avoid camera shake (although I ended up using the ASIair Mini platform in the end)
• Celestron Lithium Battery Power Tank
• Two power banks – to power the dew bands, should they be needed
• Star chart app – I use Sky Safari Pro to accurately locate the comet. 

Camera Settings

Shooting in Manual Mode and RAW file format for maximum control in post-processing, my other settings for this session were:

• Aperture: Set to its widest possible setting (f/2.8), as I find it protects me from slight coma issues at f/2.
• (ISO: Did some test shots to look at histogram and settled on ISO 800 due to the moonlight.)
• Shutter Speed: Always a balance to be had between capturing detail without blurring comet nucleus. I opted for 15” images; hoping that the star tracker will help keep the background stars as pinpoints.
• Focus: Manually focused on a bright star (Vega) using camera's Live View mode and zoom function to get a sharp focus, then carefully panned back to the comet's location. 
• Calibration Frames – depending on conditions, I’ll aim to take thirty or so "dark frames" immediately after my main images, using the exact same settings but with the lens cap on. Followed up by thirty Bias and thirty flat frames.

The end of the night’s story

For the first hour, Comet Lemmon hides — stubbornly veiled behind an unyielding wall of low cloud. I wait, sipping tea, feeling the night settle deeper around me. Then, almost miraculously, the curtain lifts. The comet appears — faint, ethereal, a traveller from the deep — and for twenty precious minutes the sky opens like a gift. It’s a race now, a dance against time and weather. The wind tugs at my jacket, the shutter ticks its steady rhythm, and above it all, Comet Lemmon burns softly in the heavens — a tiny messenger from the edges of the solar system, whispering across the void. I’m genuinely elated!

Settings on the night - Within the gap in the clouds, I managed to obtain 60 x 15” at ISO 800 f/2.8 along with thirty frames each for darks, biases and flat calibration frames. Whilst the camera was busy, I took the opportunity to record the precise dec and RA position co-ordinates – these will be needed for photometric colour calibration in SIRIL over the next couple of days. Throughout the shoot, I checked framing on each image collected.

Should I have used a light pollution filter of some form to combat the moonlight?

I debated all afternoon whether to use my Optolong L Pro clip in filter tonight. Marketed for use with comets in light polluted areas, I was very much in two minds. On the one hand, it’s great at supressing artificial light such as sodium/mercury vapour, sky glow etc. it might well improve the contrast between the comet and stars and the bright sky background.

On the other hand, the filter could reduce signal strength and introduce artifacts like halos or colour cast. In addition, the moon is a strong broadband light source which the filter isn’t really designed to suppress. So, the background may well just remain bright! There is a chance I might also wash out the comet tail details.

Given I was in a dark sky area with very little artificial urban light pollution and was aiming to use shorter exposures for later stacking, and throw in the use of a fast prime lens and the fact that the moon was far to one side of my image framing, I decided NOT to use the filter.

What would you have done in these circumstances?  Have you had success shooting a comet image? What did you do differently to me and why? Share your thoughts and tips in the comment box below so that we can continue to learn together.

As always, I hope you have found this imaging post useful. Good luck in yours, stay safe, have fun and clear skies to you all.

Steve 

So here we are - three rough and ready initial edits of the images - quickly stacked in SIRIL and quick edits in Affinity Photo.  I will spend some time on this later in the week and will do another post about my work flow. 

Want to learn more on how to shoot a comet? https://undersouthwestskies.blogspot.com/2025/10/a-beginners-guide-to-photographing.html

Want to see what my work-flow for stacking this image was in deep sky stacker? Then visit: https://undersouthwestskies.blogspot.com/2025/11/beginner-tutorial-how-to-stack-comet.html