Perseid Meteor Shower: Aperture matters! Sigma 14nn f/1.8 and Nikon D850
Introduction
Astrophotography is one of the most demanding applications we can put optical equipment through; it is in fact a torture test for any lens that has to balance aberrations across a large sensor such as APS-C or full frame, considering that a large part of the focused image will contain pin point light sources (stars). In this article I am going to detail some of the best lenses for these purposes, looking at lenses that are built to handle a wide spectrum of shooting cases. This means they will all have large apertures, to be able to deal with low light levels. In astrophotography, maximising the signal achieved from the night sky is one of the most pressing concerns when shooting, so we will be looking at lenses that function on and off of a star tracker to produce stellar results. A shooter needs to consider how they work and their goals when choosing suitable lenses / equipment. For example, if we are shooting aurora, aperture matters much more as star trackers don’t help much to gather additional signal. If we are shooting the milky way, we can use a slower lens (or a fast lens stopped down) on a star tracker. If we are shooting combinations of different items, well, this is where it starts to get tricky…
14mm and the Super Ultra Wides
Fast aperture ultra wide lenses are the lens of choice for most when they consider capturing the night sky with their camera. Ultra wides are sometimes looked down on from experienced astrophotographers, who tend to do a lot of mosaics with longer focal lengths; however I still really enjoy using them for their field of view, aperture and sheer simplicity etc. Lenses like these are excellent for strong, sky-filling aurora storms, expansive milky way views, or collective constellation shots. They are good for times when you want an expansive field of view, however do not wish to resort to a longer lens to build a pano. There could be many reasons for this, weather, time, scene geometry and more.
Sigma 14mm f/1.4 DG DN (mirrorless)
A recent design which was designed for astrophotography from the ground up. Sigma states this new optic was born from their engineers’ passion for capturing the widest, brightest, highest-resolution, and most captivating starry sky images possible. This lens is one of the best rectilinear ultra wide angle - fast aperture lenses available. It has excellent centre sharpness at f/1.4, corners are somewhat softer. It is completely useable at f/1.4, but the stars improve best at around f/2.5-2.8, with only small deformation to star shapes on the periphery and corners of the full frame image. Wide open it pretty well controlled coma and sagittal / tangential astigmatism. This lens has a massive vignette wide open (-2.5 EV corners), so you are only getting the f/1.4 advantage centrally really. It is usefully-so, quite resistant to flare compared to the Sigma 14/1.8 lens I own. It includes useful features such as a built in lens collar, and a hood which prevents lens warmers slipping into the field of view when shooting; this in combination with a manual focus lock switch, means focus stays where it was set. This lens has a rear filter slot which can be useful. It comes in at 1,170g in weight. It has an aperture ring which I love (Nikon I am looking at you) and it is fully weather sealed. As with all lenses in this class, it’s large and heavy and currently only available for Sony E and Leica L mounts.
Sigma 15mm f/1.4 DG DN Fisheye (mirrorless)
Another superb modern optical design is this. This lens is actually arguably better than any rectilinear lens when it comes to star shapes into the distant corners. It easily beats the Sigma 14/1.4 and 14/1.8 rectilinear lenses, because a fisheye lens by design does not have to bend light as much as a rectilinear lens. The result is that the corners are just better all round. It has excellent centre and corner sharpness even wide open and is useable from f/1.4 with no real problems. Wide open it has well controlled coma and sagittal / tangential astigmatism, and stars stay as tight little round circles. It includes the usual useful Sigma features, focus lock and a hood that prevents migration of any lens warmers into the field of view. This is a lens that up until recently I probably would have instantly discounted with it being a fisheye design. However, from what I have seen with this lens, it is too good to ignore. You can always get creative with those distorted foregrounds too, so give it consideration. It includes useful features such as a built in lens collar, and a hood which prevents lens warmers slipping into the field of view when shooting; this in combination with a manual focus lock switch, means focus stays where it was set. This lens has a rear filter slot which can be useful. It comes in at 1,360g in weight. It has an aperture ring which I love (Nikon I am looking at you) and it is fully weather sealed. As with all lenses in this class, it’s large and heavy and currently only available for Sony E and Leica L mounts.
Sigma 14mm f/1.8 DG HSM (dslr or mirrorless)
I have owned this lens since 2019 and it has been used to create many astrophotography pictures the length and breadth of Scotland. This lens has very good centre sharpness wide open, but soft corners, similar to the 14/1.4 lens described above. Wide open it has noticeable coma and sagittal / tangential astigmatism, giving little wings to the stars. I use this lens wide open, and on pixel peeping we can see these aberrations clearly. Stopped down they improve quickly however, and get close to the newer sigma 14mm 1.4 design at 2.8 (this is a consideration when using a star tracker of course, we can stop down to improve star sharps and vignette’s etc). This lens is no slouch, even in comparison to the newer 1.4 design. (For example, mid-frames actually favour the 14mm f/1.8 Art slightly). Like most fast ultra wide lenses, this lens has some noticeable field curvature to it’s design. This means that we have to be careful focusing centrally. If we choose a focal point 2/3 out from the centre frame, we can get a better sharpness balance and control some of the corner aberrations (and sharpness), much better. This lens like the others, is large and heavy, and still fairly expensive despite being older. This lens comes in at 1,120g in weight. It has an aperture ring which I love (Nikon I am looking at you) and it is fully weather sealed. As with all lenses in this class, it’s large and heavy and currently only available for Sony E and Leica L mounts. It has one advantage over the others, in that it can be used on DSLR and Mirrorless cameras, if that matters to you, which for me does. It is available for Nikon F or Canon EF mounts, and can be adapted to any mirrorless system with the usual adapters. I use it on DSLR and on Nikon Z mount via the FTZII adapter.
Sony 14mm f/1.8 GM (mirrorless)
And here we come to a real surprise. Optically speaking, for astrophotography, I have to hand it to the Sony 14/1.8 mirrorless lens for E mount cameras, it is very good optically and much smaller than the others. I have seen some places state it is the best 14mm in terms of overall performance. It’s a great lens, however it is a little more nuanced than this. It does have clean, and fairly most pinpoint stars into the corner frames, yet of course it’s not a 1.4 like the Sigma mirrorless option, but it is much lighter (460g!). It tests slightly less sharp in the mid frames and corners than the other options, however it proves that testing for the intended subject and not relying solely on MTF charts and resolution figures is the most sensible approach when evaluating a lens. What is most astounding is this lens is about half the size and weight of the other options mentioned here at just 460g. It also includes an aperture ring which is very nice to have, usual full weather sealing and as mentioned it is tiny relative to the other options. This is a huge boon for this level of performance. If shooting Sony, it is probably a no-brainer, I would potentially choose this over any of the Sigma designs. Then again, I am a bit of an aperture nut so, maybe that f/1.4 would entice me, for Aurora. It can be adapted to other mounts, eg Z, however I caution you on doing so. Often we cannot achieve the right back focus due to different sensor stack thickness. The end result is the corners seem to play much better on the native mount when it comes to mirrorless lenses. For use on Sony E mount.
Nikon 14-24mm f/2.8S (mirrorless)
Ah, the famous ultra-wide zoom. This is probably the best one out there due to it’s relatively small size and weight compared to lenses in it’s class. At just 650g, it is well built, works extremely well on the Z mirrorless system, and it is optically the best fast ultra-wide angle zoom that I know. It even closely matches with the best sigma prime at f/2.8, no mean feat! This said though, it is a f/2.8 lens. This is the minimum I want out of an astro lens, and luckily, we get this here (forget about f/4 glass). Optically this lens is superb, even on starlight. It is best with regards to star performance at 14mm, however most of the range is good. It is weakest at 24mm, however even at it’s weakest it is still strong when it comes to astro. If you can handle the slightly slower aperture than the primes, this lens is arguably a lot more flexible. There is also of course the option to use it on a star tracker to negate the aperture difference for certain shooting. However, when shooting Aurora or meteor showers etc, we actually want the large apertures of f/1.4-f/1.8 to draw in that light. So choose wisely, based on what do you. I’ve got this lens and the 14/1.8 for that reason. It makes a big difference! I have been doing this for some time now, so have amassed different equipment for each application. See here for more. This lens is made for Nikon’s Z mount and it really is as good as I am stating here.
Orion over the Duncansby Sea Stacks, 14-24/2.8S with a Nikon Z8
20mm
20mm is a classic astro focal length, it is perfect for singular fields of view that include a good amount of foreground (remember we have access to vertical shooting), and it also works well on a tracker. Their field of view, whilst expansive, ‘chops off’ some of that really distorted look we can find at 14mm.
Sony 20mm f/1.8 FE (mirrorless)
This is a great choice if shooting Sony. It is pretty much a class leading lens for a 20mm design, and it’s only real competitor would be the Sigma 20mm f/1.4. However, this lens simply sharper across the full frame at any shooting distance than the Sigma, but it has a little more coma and corner aberrations relevant to astrophotography. These are not severely worse than the sigma, but worth noting. These two are very close in terms of performance otherwise. The main difference is the slower aperture of the Sony, however for that we get a smaller and lighter lens. It’s a case of make your choice as to what matters for you. (The sigma does have that cool lens heater retainer that I like)…It includes useful features such as an aperture ring, and full weather sealing. This lens is tiny, and it comes in at just 375g in weight. Sony have really nailed a balance between optical performance and weight, even despite the fact they have the most restrictive (narrowest throat) mount out there. It has an aperture ring which I love (Nikon I am looking at you) and it is fully weather sealed. Designed for use on Sony E mount.
Sigma 20mm f/1.4 DG DN (mirrorless)
Here is a class leading lens for astrophotography. This lens wins out over the Sony f/1.8 mirrorless version because it has better star performance in it’s corners over it (think coma, astigmatism, CA etc). This has a nice little ‘lens heater retainer’ at the end of the barrel to prevent it slipping into the field of view. Great ergonomics are found here. It includes useful features such as a built in lens heater retainer; a hood which prevents lens warmers slipping into the field of view when shooting; this in combination with a manual focus lock switch, means focus stays where it was set. This lens has a rear filter slot which can be useful. It comes in at 635g in weight. It has an aperture ring which I love (Nikon I am looking at you) and it is fully weather sealed. As with all lenses in this class, it’s large and heavy and currently only available for Sony E and Leica L mounts. It is larger and heavier than the Sony, however if I owned a Sony body, this would still be a strong contender as my lens of choice due to the expansive feature set and optical performance.
Nikon 20mm 1.8S (mirrorless)
Contender for one of the ugliest and most basic lenses I have ever seen on it’s exterior, the Nikon 20 1.8S lies somewhere in the good category for astro shooting as noticed by most reviewers such as Lenstip who do excellent diode tests to show coma and astigmatic problems in lenses. It fails to correct astigmatism and coma as well as the Sigma or the Sony. I find this odd because I expected more from Nikon’s Z mount; I mean they shoved that mount advantage right in my face day one, so why are the other two designs that work on the smallest E mount, arguably better for astro? (Remember that we can often improve corner aberrations by focusing well off centre and checking the corner stars). It also has strange ergonomics; it has a focus ring that would make a toddler blush at it’s size, making it easy to knock focus unintentionally in the dark. I can’t see any real reason for this, but it’s a bit strange looking and as you can probably tell, ergonomically I am not a fan of this lens. It is also very long, which was a design to combat focus breathing for video. If you don’t care about video, you’d prefer the Sony over this. It has no focus lock, and has only one lens switches on the barrel to switch focus from manual to auto. A small plus to the fact it has a distal barrel design which should stop lens heater migration. I think Nikon farmed this design out, and where just happy it was better than the 20mm 1.8S. It has a reasonably low weight of 505g and belongs on Z mount for shooting.
Loch Tummel, Scotland. 20mm Mosaic Image
24mm
24mm is an astro focal length that can begin to isolate a deep sky object or constellation, whilst still leaving some foreground in shot. It can also be used to construct mosaics, producing ultimately more detailed views of the cosmos than using a lens such as a 14mm prime.
Sony 24mm f1.4 GM (mirrorless)
Here we have a clear class leader if you shoot on Sony E mount. This lens has basically no coma or astigmatism wide open. Very impressive, considering the lens is an f/1.4. This enables it to be used for aurora to collect the best light, and stop motion. It is of course excellent on the milky way, constellations, and any other starlight scene we can throw at it. It does have some CA wide open, with the effect disappearing around f/2. (This is an aberration which is very easy to clean in post processing anyway). It includes useful features such full weather sealing and comes in at a paltry 450g in weight, making it great for carrying. It has an aperture ring which I love (Nikon I am looking at you) and it is fully weather sealed. As with all Sony lenses for astro, keep them in E mount land.
Sigma 24mm f/1.4 DG DN (mirrorless)
The Sigma 24mm doesn’t beat the Sony here in terms of outright astro shooting, however for me, it is a clear winner over the Nikon option listed below, since it has both an f/1.4 aperture, and a better control of corner aberrations than it. It has other advantages too. This lens keeps it’s switches and focus lock like the others and shouldn’t allow lens heaters to migrate into the frame when using the hood. It has great ergonomics in fact, also sporting an aperture ring like the other Sigma lenses in this new range, along with full weather sealing. It comes in at a very reasonable 520g in weight. It can be used on Sony E or Leica L mounts with no issues.
Nikon 24mm 1.8S (mirrorless)
At present, this is the best Nikon 24mm for astro on Z mount. It has much less astigmatism (aberration causing winged stars) and coma than the old f mount 24/1.4G and 1.8G lenses, however curiously it is still not perfect, and not as good as the Sony. Again, Z mount advantage? What is going on here Nikon? I do wish it had an f/1.4 aperture however. I do not own this lens, and still use the 24mm 1.4G as I tend to use that lens between dslr and mirrorless cameras. One thing I dislike slightly about some of Nikon’s prime lenses is this simplistic approach in their ergonomics. Like the 20mm 1.8S, there are hardly any switches on the barrel; no focus lock like Sigma, a little area at the end of the lens to prevent migration of a lens heater maybe, but still…Why are the focus rings on Nikon’s wide prime lenses seemingly designed for toddler’s fingers? They are massively oversized, making it easier to knock focus by mistake at night. This is a definite downside to Nikon options I am finding, in particular for astro as it can really affect things. This along with the lack of a lock switch, means you really need to be careful of accidentally ‘adjusting’ focus when you don’t wish to at night.
Meteor Spears Auriga. 24mm f/1.4G shot at f/5. Separate 24mm shot for ground with star tracker off. 24mm is a very useful astro focal length
35mm
35mm is not often considered an astro focal length, particularly to beginners. This is because many beginners are stuck on the ‘you need to go wide’ thing for astrophotography. 35mm lenses are great for light collection (they collect vastly more light than a 14mm 1.4 lens - remember that aperture is a ratio of focal length, see the rest of the blog for more detail on this). 35mm lenses are also superb for constructing detailed sky mosaics on a star tracker.
Tamron 35mm f/1.4 Di USD (dslr or mirrorless)
Hands down, this one is the best 35mm optic for 35mm format across all brands. See here and here for on this lens. I do not say this lightly, however there are a number of factors that bolster this statement. One is aperture. Even at f/1.4, this lens can be used with considerable confidence, and is pretty close to perfect right out to periphery of the frame and corners. Stars stay tight and rounded with very minimal problems. This is a optical feat in itself at such a fast aperture of f/1.4. This lens is extremely well built and feels great in the hands (fighting a ‘that’s what she said’ here; I took the moral high-ground). Total weight comes in at 805g and it has a sole MF / AF switch on the barrel of the lens along with the dslr standard window to see focal distance. The hood is excellent and locks into place, the lens has full and extensive weather sealing also. This lens can be found for Nikon or Canon dslr mounts, thus it can be used easily with adapters on their respective mirrorless systems. It does get a little long (dammit, twice in one paragraph!), however it really is no problem if you are out there for optical excellent, I highly recommend it. I use it directly on F mount or on the Z system via the FTZII.
Voigtlander 35mm f/2 APO-Lanthar II (mirrorless)
Another class leading 35mm prime lens, the Voigtlander has the large advantage that it is smaller and lighter than the Tamron. However, it does lack weather sealing, which is a big minus point considering dew formation and inclement weather conditions we sometimes face in the field. This lens is well corrected (it is an APO design), however the 50 is a tad more controlled in the corners when it comes to the biggies like astigmatism and coma that affect our domain. The other problem is that it is ‘only’ an f/2, and Tamron has shown that we can beat this performance at f/1.4. This is still an excellent lens, well build, light at only 420g and comes with a beautiful manual focus ring to get that focus just right. It has been officially licenced and is available on Nikon Z mount directly, and it is also available on E mount.
Planetary Parade over Rural Scotland March 2025. A huge mosaic shot with a Tamron 35/1.4 lens and Nikon Z8 Camera
Milky Way over Dunnet Head, Scotland. Sigma 35mm 1.4 Art on a Nikon Z8. Notice the lack of astigmatism in the corners? I used post processing to fix this optical defect that renders stars into ‘seagul’ shapes. This is still a functional lens, however has been replaced by the Tamron 35.
50mm
50mm lenses are even less thought of as astro lenses compared with 35mm primes. I will admit it is my least used lens for astro-landscape style shooting. However, this is simply down to the numbers. I simply shoot many more views with wider lenses. There is one exception. Every year I use a 50mm lens in order to create a milky way core mosaic as it rises in late March - early April around 4am.
Voigtlander 50mm f/2 APO-Lanthar II (mirrorless)
A class leading 50mm prime lens, the Voigtlander has the large advantage that it is smaller, lighter, better built and optically trumps the competition. However, it does lack weather sealing, which is a big minus point considering dew formation and inclement weather conditions we sometimes face in the field. This lens is extremely well corrected and can be used wide open. The star shapes are great into the far periphery and corners on full frame. This lens does have a huge vignette wide open, and it does mean that the collected signal in the corners is significanty poorer than it could be. I assume this is due to the fact the lens was designed to fit not only the Z mount (which it of course does easily), but also the significantly narrower E mount diameter. The other ‘problem’ is that it is ‘only’ an f/2, and Tamron has shown that we can beat this performance at f/1.4 if we have the design intention to do so. This is still an excellent lens, well build, light at only 370g and comes with a beautiful manual focus ring to get that focus just right. It has been officially licenced and is available on Nikon Z mount directly as well as Sony E.
The Milky Way Rises over Dunnottar Castle - Stonehaven, Scotland. Made possible with a 50mm lens on a star tracker.
The Milky Way Core over a secluded Beach. A huge 50mm mosaic bringing out fantastic sky details with no distortion.
Then after we have considered all this, we can use many of these lenses in a deep sky style of shooting. Here are some pictures I have made over the last few years with a star adventurer and dslr / mirrorless lenses:
Mars and Pleiades Conjunction. The first deep sky astro image I ever took. Nikon D850, 70-200/2.8E. 20 Minutes total exposure
Cygnus. 50mm f/1.4G at f/4. About 2 hours total exposure