What's in the night sky for December 2025?

 What’s in the night sky for December 2025?

December 2025 features the Geminids meteor shower peaking around December 14th, the Super Cold Moon on December 4th, and the winter solstice on December 21st. Key celestial objects to find are bright Jupiter in the east and Saturn in the west, with Mercury visible in the morning sky before its greatest western elongation on the 7th. 

Meteor showers

• Geminids: A major highlight, peaking around December 14th with up to 120 meteors per hour possible.
• Astrophotography tip: The peak occurs when the Moon is a thin crescent, providing excellent dark skies for capturing this shower.
• The Ursids:  Also active, peaking around December 22nd with lower rates (up to 10 meteors per hour). 

Planets

• Jupiter: The brightest object in the evening sky, visible in the east after sunset and moving towards opposition in January.
• Saturn: Visible in the south-west in the early evening. It sets earlier in the month as December progresses.
• Astrophotography tip: Look for the Pleiades and Hyades star clusters in the constellation Taurus
• Mercury: Best viewed in the pre-dawn hours in the southeastern sky, with its greatest western elongation on December 7th.
• Neptune: Will require binoculars or a telescope to spot, located near Saturn in the constellation Pisces. 

Other events

• Super cold moon: The Full Moon occurs on December 4th and is a Supermoon, meaning it appears larger and brighter than a typical Full Moon.
• Winter Solstice: Occurs on December 21st, marking the shortest day of the year in the Northern Hemisphere.
• Andromeda Galaxy: Can be seen in the southern sky on darker nights. 

Astrophotography tips

• Meteor showers: The Geminid meteor shower is ideal for photography due to its high rate and the favorable moon phase.
• Planets: Consider capturing Jupiter or Saturn, but remember they are best viewed from a location with less light pollution.
• Deep sky objects: The Andromeda Galaxy and the Pleiades star cluster are excellent targets for astrophotography, but require darker skies. 

1st Dec		This blog gives some excellent astrophotography targets for the month: https://starwalk.space/en/news/december-deep-sky-objects
2nd	Ganymede’s shadow crosses Jupiter’s disc 0610 – 0925.	This website adds further to the calendar details shared here: https://starwalk.space/en/news/night-sky-tonight-december
4th	98% lit waxing gibbous moon occults M45 Pleiades from around 0300. Uranus is 4.6” south of the moon at this time. Full moon at 2315 – a perigee full moon today	If you want to image Orion during December, this website gives so good targets to try and image or visually observe: https://elanvalley.org.uk/uncategorized/eyes-on-the-night-sky-december-2025/
6th	Ganymede reappears from behind Jupiter around 0235
7th	Mercury reaches greatest western elongation – 20.7 degrees west of the sun in the morning sky - meaning it is at its farthest point from the Sun from our perspective.  87% lit waning gibbous moon this evening – sitting 3.5 degrees from Jupiter around 1900.	The ideal time for spotting Mercury will be just before dawn on 7 December, looking to the east. However, its not prudent to observe Mercury through a telescope as it will be very close to the sun and you risk pointing your scope directly at the sun as it rises
8th	Titan transits Saturn between 1730 – 2350 Callisto begins transit of Jupiter between 0210 and 0620
9th	Low altitude views of Saturn around 2348. Should see Titan and Rhea as well.
10th	Regulus is occulted by the 66% lit waning gibbous moon around 0718 during brightening dawn twilight
12th	Ganymede is eclipsed by Jupiter’s shadow around 2355 – reappearing around 0558 on 13th.
14th	Peak of Geminid meteor shower – with little interference from the moon (in a waning crescent phase)
16th	Titan occulted by Jupiter’s globe – 1623. Reappears 2205. Callisto occulted at 0744. Ganymede completes transit of planet – 1800 to 1950
21st	December Solstice
22nd	Peak of Ursid meteor shower
23rd	Ganymede’s shadow transits Jupiter’s disc 1947 to 2308. Ganymede does its transit 2120 to 2309
24th	Titan transits Saturn 1625 to 2305 Io, Callisto all transit as Jupiter rises.
25th	Watch out for Santa and his sleigh transiting everything after dark!
30th	Ganymede’s shadow crosses Jupiter’s disc 2158 to 0123 on 31st. Ganymede itself transits 2300 to 0228 on 31st.

Sources "Sky at Night" and "High Scientific"

Imaging session on NGC 1499 The California Nebula

 A Night in the Back Garden Under the Stars

Target: NGC 1499, the California Nebula
Mood: Mischievous Backyard Astronomer

There are glamorous observatories on mountaintops… and then there’s my back garden: a patch of grass with a steep incline above it, and a band of trees that act like they own the southern horizon. A slice of sky that runs from the northwest around to the east. Everything else? Hidden behind a wall of woodland darkness, as if the universe pulled a curtain halfway across the stage. Frustrating? Absolutely. But also, oddly charming.

I often joke that imaging from the back garden is lazy astronomy—as if I’m somehow cheating the grand tradition of freezing atop windswept hillside car parks. Yet, every time I do it, I feel delightfully wicked, like a child raiding the biscuit tin when no one was watching. No packing the car. No driving at ungodly hours. Instead, I get to nip inside for a cuppa or catch a bit of TV while the mount gently whirrs away outside under the stars. The nightscape? Hooting owls, prowling cats, and the occasional fox strolling down from the woodland like it’s popping by to check on my guiding graph.

Shamefully luxurious behaviour… and I adore it.

A few months ago, in the spirit of “back garden decadence,” I upgraded the observing area. I installed three perfectly spaced patio slabs for my tripod. Then I brought some colourful 12mm children’s foam jigsaw mats to lay across the decking. Functional? Extremely. The deck turns into something between a skating rink and a death trap this time of year, and those mats keep me from performing accidental gymnastic routines while carrying expensive optics.

So, a few weeks back, on a crisp moonless night, I finally aimed for NGC 1499. From the kitchen table (aka mission control), I could see the mount through the window while stirring hot soup and basking in the warm red glow of my head torch. I seem to feel the cold more these days—an unexpected betrayal, considering how many winters, long ago, I spent stomping through snowfields or dangling from an ice axe on frozen waterfalls. Back garden astrophotography, therefore, feels like a snug loophole in the universe’s rules.

Despite the suburban light pollution, I managed several solid hours on the nebula over two nights. Below is the kit list for anyone curious—or for future me, when I inevitably forget which power bank ran what.

 

Equipment

• Canon 800D with clip-in Optolong L-eNhance filter
• William Optics Zenithstar 61II with 61A field flattener
• Sky-Watcher EQM-35 Pro mount
• Guiding: ASIAir Mini + ZWO 120mm guide cam + RVO 32mm guide scope
• Celestron Lithium Pro power tank
• Dew bands on main and guide scope
• Two small power banks dedicated to dew bands
• Dummy battery + power bank for the Canon 800D
• MSM green laser pen with polar alignment adapter
• Sky-Watcher right-angled polar viewer
• Neewer intervalometer

 

Imaging Data

Night One

• 30 × 360" lights
• ISO 1600
• 12 darks
• 20 bias
• 30 flats

Night Two

• 43 × 360" lights
• ISO 1600
• 15 darks
• 20 bias
• 30 flats

Guiding behaved surprisingly well for an un-serviced, third-hand mount. The RA axis is a little stiff – a bit like me – a ‘sometimes’ reluctant older bloke getting out of a comfortable chair. Nothing disastrous with guiding - RA hovered around 0.80, DEC around 0.90. Honestly, not bad considering I’m still getting acquainted with the ASIAir Mini and its app.

This was my very first rough post edit of the data and I’ll update this post further once I process the images properly; and I will share my full workflow - warts, wonders, and all. Stay tuned for a hopefully better edited California Nebula in all its crimson glory!

As always, collecting the data is the easy bit

Post editing is a dark, dark art though! 

I am still getting to grips with how SIRIL v1.2.6 works. Throw in GraXpert and then also learning how to use Affinity Photo 2 - and it all fries my brain.

As always, the same issues are cropping up in my post editing work flow - over stretching, noise etc. 

On the bright side? Two years ago I knew absolutely nothing about photography, astrophotography, basic astronomy - so I am making some progress - all be it is small baby steps! 

Postscript:

Since processing the above image - I have had another go studying Siril and refining my workflow. I have also started to understand Cosmic Clarity Suite Pro as well from Seti Astro 

So - here is my second edit on the data using the above programs - 

This image has used Veralux Hypermetric Stretching

This is supposed to use all of the availabe data captured and is more colour realistic 

I am just finishing researching and writing up my final workflow based on Siril -GraXpert-Cosmic Clarity - Affinity Photo and when finished I will put it in a post. 

Which image do you like best and why? Which one do you think is the most realistic? Do you use the above programs - if so do you have any tips to share? As always, drop a comment in the box below - I'd love to hear your views. In the meantime, cl;ear skies to y ou all, stay safe and have fun out there observing

Steve 

Equipment review: Samyang 14mm f/2.8 manual focus lens for milky way landscapes

 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 

Samyang 14mm f/2.8 (Manual Focus) Review for Astrophotography

(Also known as the Rokinon 14mm f/2.8 in North America)

When it comes to astrophotography gear, we all have our checklists — usability under the stars, optical performance, portability, and durability. After all, we’re not just taking photos; we’re venturing into the dark, chasing starlight. But what really matters most in the field? And where does this budget-friendly wide-angle fit in?

In this review, I’ll:

• Give an overview of the lens
• Outline its main strengths
• Discuss its weaknesses
• And share my verdict on whether it’s worth it for beginner astrophotographers

Let’s dive in.

Overview

The Samyang 14mm f/2.8 ED AS IF UMC has earned a bit of a cult following among night-sky enthusiasts. It’s the kind of lens that shows up in countless astrophotography bags.

With its ultra-wide 14mm field of view and fast f/2.8 aperture, this lens captures sweeping nightscapes — from horizon-to-horizon Milky Way arcs to vast fields of stars. Despite its modest price, it punches well above its weight, capable of producing breathtaking images when treated with care. Some of my personal best Milky Way shots have come through this lens.

Key Specs:

• Focal length: 14mm (full-frame) / 21mm (APS-C equivalent)
• Max aperture: f/2.8
• Focus: Manual only (no autofocus or electronic contacts)
• Construction: 14 elements in 10 groups (3 high-refractive, 2 ED)
• Filter thread: None (bulbous front element)
• Weight: ~530 g
• Angle of view: ~115° (on full-frame)
• Weight - around 550g
• Material - mainly made of plastic 

Just look at all that glass. This lens is an absolute 'light gathering' beast

Strengths for Astrophotography

1. A window to the cosmos
At 14mm, the field of view is wide enough to swallow the Milky Way whole. On a full-frame camera, you can often fit the entire galactic core and horizon in one shot. This makes it ideal for those grand, cinematic night landscapes — the kind where the sky feels like an ocean and the foreground and tripod is your anchor

2. Excellent value for money
At around £250–£300, it’s hard to beat. It delivers genuine ultra-wide performance without breaking the bank — a rare find in astrophotography. It’s often the go-to “first Milky Way lens” for beginners on forums like Cloudy Nights and r/Astrophotography. One user summed it up nicely: “Cheap, manual, and sharp where it counts.”

3. Respectable coma control (for the price)
Even wide open at f/2.8, stars stay round and well-behaved in the centre, with only mild stretching toward the corners. It’s not flawless, but for its price class, it’s impressively restrained.

4. The beauty of manual focus
Because this lens is purely mechanical, there’s no risk of focus drift or accidental AF hunting in the dark. Once you’ve found that perfect infinity point (usually a hair before the hard stop), you can tape the ring and shoot all night. It’s wonderfully simple — one less variable to worry about under the stars.

5. Built like a tank
The all-metal construction and smooth focus ring make it feel solid and reliable. When you’re out in cold, damp, or even frosty conditions, fewer electronics mean fewer things that can go wrong.

Let's talk lens cap. Not one that easily slips into a trouser pocket is it?

Designed to fit over the large front petal rimmed lens area. 

As a consequence two things to be aware of - firstly - no screw threads for filters; and secondly - a nightmare if you want to do calibration frames as the petal design lets light through in the 'gaps'. 

Although I haven't done it yet, on my 'to do' list is cutting down a 3D printed bahtinov mast to fit around the petal hood to negate this issue. 

Weaknesses and Limitations

1. Heavy vignetting
At f/2.8, corners can be about 3 stops darker than the centre — something you’ll definitely notice in unprocessed Milky Way shots. Think of it as a flashlight beam effect that you’ll need to balance out in post-processing.

2. Soft corners
The centre sharpness is excellent, but the edges do suffer a bit of coma and stretching. Stopping down to f/4 or f/5.6 improves things, though at the cost of longer exposures or higher ISO.

3. Moustache distortion
The lens exhibits a distinctive “moustache” distortion — wavy and complex, especially visible with straight horizons or architectural elements. It’s mostly irrelevant for deep-sky shots, but if you like including landscapes or structures, some post-correction may be needed.

4. No electronic communication
No EXIF data, no aperture readout, no autofocus. Everything is manual. For astrophotography that’s fine — but worth noting if you’re used to modern digital convenience.

5. Filter limitations
That bulbous front element looks cool but makes using filters tricky. You’ll need a special 150mm holder if you want to use ND or gradient filters. For Canon DSLR users, clip-in filters are a handy workaround.

6. Sample variation
Quality control can be hit or miss — some lenses have slight decentring or uneven sharpness. Buying from a reputable retailer with an easy return policy is your best safeguard.

7. An inaccurate focusing ring 

On my lens, the focus ring is slow to rotate making manula focus adjustments at times tricky. The apparent depth of field is very large and so I find myself having to focus stack the foreground at times, using 'live view'. And, maybe its just my particular lens, but does anyone else find that the distance scale on the ring doesn't seem very accurate? I never just set it to infinity - as infinity - in reality seems to be a little bit back off the mark, hence the taped remninder ytou see on my lens cap! 

My Experience

This has been my main Milky Way lens for a while now — and honestly, it’s been a joy. On a tripod, it handles 15–30 second exposures beautifully. My copy shows only mild coma, easy to fix in post. Stars remain crisp and defined at f/2.8, which is usually where I leave it.

Mounted on a tracker, it shines even more. Sixty-second exposures are clean, and detail in the galactic core pops beautifully. I always tape the focus ring once it’s dialed in — a small ritual that pays off every time.

Verdict

For me, the Samyang 14mm f/2.8 has been one of the best investments I’ve made in astrophotography. It’s affordable, reliable, and capable of truly inspiring results. It’s not perfect — few things at this price point are — but it rewards patience and good technique. Think of it as a sturdy workhorse: not glamorous, but tireless and dependable.

For beginners, it’s a brilliant first step into the night-sky world.

If you’re ready to spend more, however, consider alternatives like the Sigma 14mm f/1.4 DG DN Art — purpose-built for astrophotography and two stops faster, allowing lower ISO and shorter exposures. The Sigma 14–24mm f/2.8 DG DN Art is another stellar (pun intended) option with great corner sharpness and flexibility, though it’ll cost you several times more than the Samyang.

Bottom line:
The Samyang 14mm f/2.8 is like a well-loved telescope — simple, rugged, and surprisingly powerful once you learn its quirks. For anyone looking to capture their first Milky Way, it’s a gateway to the stars.

Taken last year with my samyang 14mm lens

Equipment review: - A review of the ASIair Mini from ZWO

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

Some pieces of equipment feel like they earn their place in your kit bag. Others, feel like they deserve a small shrine to techie ingenuity!

My ASIair Mini is one such beastie which needs a shrine! A palm sized marvel of technology that punches above its weight. Equal parts tech wizardry and control tower, in this blog today, I review my ASIair mini, 9 months on from purchasing it. The good, the bad and occasionally the plain baffling! So, I’ll cover

·       A very quick tour of its key features

·       Outline its standout advantages

·       Examine its quirks, drawbacks and disadvantages

·       Review what other users and reviewers say about it

·       Who I think the ASIair Mini suits

And, if you are new to the ASIair Mini cosmos, you might want to also check out my beginner’s tutorial to setting up and using the ASIair mini on your own rig.

https://undersouthwestskies.blogspot.com/2025/02/beginners-guide-to-using-autoguiding.html

Copyright for all images  - Alan Dyer on Cloudy Nights forum

So, let’s start with:

Features I like

Hardware & connectivity – is it the Swiss army knife of astrophotography hubs? Let’s find out.

• Compact size & light weight. It really does fit in the palm of my hand and is lighter than many eyepieces I own
• Made of CNC-machined aluminium, giving a sturdy, dust/dew-resistant body. It just looks compact, elegant and efficient (I’m so shallow!). A ’premium gear’ vibe.
• Built-in WiFi antenna supporting 2.4GHz and 5GHz for wireless control from phone/tablet.
• USB Type-C port (for e.g. connecting to computer or export) and 4 × USB 2.0 ports.
• Four 12V DC output ports (to power accessories such as camera, dew heaters) and a DSLR shutter release port.
• Power monitoring: A mini mission-control in the palm of your hand - the unit allows monitoring of input voltage/current, and reports temperature, devices connected etc. Not just smart, its ‘thoughtfully’ smart!
• Software/firmware features: Plate-solving for alignment, polar-alignment routines, focusing assistant, multi-target planning, image stacking on-device (for supported cameras) etc.
• Storage: Internal eMMC storage (e.g., ~32 GB) for saving captures. But you can use a usb stick in one of the usb ports as well

 

Workflow & usability

Tired of a spaghetti mess of cables, laptops, power bricks? The Mini may well feel like a breath of fresh night time air for you!

• You can use a smartphone or tablet (iOS or Android) to control the camera, mount, guiding, focus, filter wheel etc. Moreover, I can do it from the kitchen! Make a cuppa, keep warm, monitor everything happening outside – its living the dream!
• All-in-one imaging hub: The Mini replaces a laptop + multiple control boxes + messy cables with a simpler one-box solution. A simple portable rig without a power-hungry laptop etc – brilliant.
• Good WiFi range: I can go back in the house, sit in the kitchen and it still works.
• Imaging feature set: The app supports tasks like focusing (with curves/HFD), plate-solving, dithering, calibration frames, filter switching, auto-guiding, multi-target sessions. Confession time – I haven’t even scraped the surface of some of these functions yet! I literally learn something new every time I use it!

 

Here is my take on advantages, but I also researched this on some of the popular forum threads.

Advantages (What the Mini does well)

1.      Simplified setup & workflow
It took me a couple of sessions to work out the basics. Like deciphering hieroglyphs, but that maybe because I’m a tad dim. It does make astrophotography much easier — especially for deep-sky imaging – centralising everything and reducing cable clutter, eliminating the need for a laptop etc. It’s probably the simplest and most user-friendly controller around.

2.      Portability & power efficiency
So compact and low-power compared to a full laptop – brilliant for my “grab-and-go” setups. The aluminium body makes it robust for field use and a good WiFi range gives flexibility in positioning. It is easy to switch between my two rigs. A backpacking astronomer’s dream!  

3.      Integrated control & monitoring
Many reviewers and users commented on the fact that having power-ports, USB ports, monitoring of voltage/current etc means you can run camera, mount, focuser, heaters etc from one hub — reducing separate controllers. It’s a conductor orchestrating your astrophotography symphony. Now, I haven’t done all this yet – mine acts as a hub connecting the mount, guide camera and DSLR camera (which it does easily). I run dew band heaters from a separate power pack. Autoguiding and dithering run very well by the way. Basically, it has plenty of bells and whistles for beginners new to astrophotography to be getting on with.

4.      Strong value
Weigh up its capabilities against its price and its real value for money. The price point relative to capability is often mentioned in reviews. I got mine bundled with the ZWO 120mm mini guide cam and also a guide scope.

5.      Good support for ZWO ecosystem
If you already own ZWO cameras, focusers, filter wheels etc, then the integration is generally ‘plug and play’ heaven – seamless integration.

 

What comes in the box 

Now there are disadvantages with the ASIair Mini; its less shiny side is where it gets a little tricky – some are to do with the unit itself but many are to do with the control app. No product is flawless and the Mini is no exception.  

Disadvantages / Limitations (What to watch out for)

No product is perfect, and the Mini has several caveats noted by users & reviewers and me for that matter.

1.      Hardware compromises (to achieve “Mini” size/price)

o   The USB ports are all USB-2.0, not USB-3.0. and some reviewers note that full frame cameras will not work with the live stacking feature.”

o   The unit lacks some features of the larger ASIAIR Plus/Pro models: e.g., there is no Ethernet port.

o   Because of its simplified / cost-cut design, some more advanced features and high-end workflows may be constrained. Not ideal then for ultra-demanding setups.

2.      Ecosystem lock-in
A frequent criticism: you are somewhat locked into the ZWO ecosystem (cameras, focusers, filter wheels) if you want full functionality. The Mini plays nicest with its own family! Software not including drivers for cameras, focusers, or filter wheels from competing manufacturers and where it does occasionally occur, you aren’t guaranteed full, smooth integration. My tip? Do a compatibility check before buying if you have non-ZWO gear already.  

3.      Software/firmware stability & glitches
Some users report bugs, wireless disconnects, or setup quirks. And this is a major issue I feel – put it this way, once I got mine set up and working, I switched off automatic update on the app. Why? Some of the app upgrade releases have on occasions come with bugs, stability issues, random disconnections and more. It isn’t often but it is frustrating when it happens.

4.      Power supply caution
The Mini needs a proper power source – ideally 12V/5A. Underpower it and you risk instability. A power bank of say 12V/1.5 could endanger the electrical integrity of the ASIair. Hence, I run dew band heaters off a separate power bank, just to play safe.

5.      Not optimal for very high-end / high-speed camera workflows
Running a large camera sensor? Doing high speed planetary imaging? The USB-2 ports become a bottleneck if you are trying to connect many accessories such as camera+guide cam+focuser+filter wheel+USB stick.  The Mini may struggle in workflows that demand very fast data transfer, live-stacking full-frame cameras etc.

6.      Avoid “cheap” cables/adapters that may cause voltage drop or mis-outputs.

7.      App/User-interface quirks

o   Some beginner users find the app somewhat unintuitive initially and mention that the downloadable PDF manual is lacking specifics, outdated and rather vague on some important aspects. I really had to rely on YouTube experts and then draw up my own guide sheet when first using it as there was so much to take in. I strongly urge you to check out my other post with its videos and ‘cheat sheet’.

o    Plate solving bugs with the ASIAIR mini crop up - completely failing GoTo – is one I occasionally experience it’s as frustrating. The telescope develops schizophrenia, traversing in a seemingly random direction, confirming a plate-solve on your target but pointing to a completely different area of the cosmos. Makes me a very confused stargazer at times!  My solutions have been to check the sequence of powering mount vs the Mini. (Turn on the ASIAIR Mini first, then mount/power gear. Also, make sure plate-solving and GOTO are correctly configured; check mount parameter settings, orientation, and that image orientation is correct.)

o   Freeze firmware updates if you have a working setup. Some users recommend not updating immediately after app/software releases or waiting to see feedback in forums after a release. As I have already said, miner is permanently frozen on one version and I haven’t updated it since, with no ill effect thus far.

 

Recommendations: What rigs the ASIAIR Mini suits (and which it doesn’t)

OK, getting into dangerous territory now, as I am still a beginner to this, but here are my thoughts:

Best suited rigs

The Mini is particularly well suited to:

• Portable / field rigs: especially “grab-and-go” setups where you want minimal cables, quick setup, remote control from your phone/tablet.
• Deep-sky imaging with mid-sized sensors: If you have a camera of moderate size (e.g., APS-C or smaller), and you are doing exposures of a few minutes, the Mini will work well as the hub controlling mount guiding, camera, focuser, filter wheel.
• ZWO ecosystem users: If your camera, focuser, filter wheel etc are ZWO branded, the integration will be smooth and you’ll benefit from the Mini’s streamlined workflow.
• Simplified rigs / beginners: For someone looking to avoid the complexity of a full PC + multiple control software, the Mini gives a more “plug-and-play” experience and is a good choice for those who want quick results. No headaches here!

A very similar set up to my own rig

Less suited rigs / when to consider something bigger

You might consider a more advanced controller (or a full PC) instead of the Mini when:

• You are using large-format sensors (full-frame or very high-megapixel cameras), or doing high-speed imaging (e.g., planetary, lucky imaging) where USB 3.0, more bandwidth, and faster I/O matter.
• Your gear is heterogeneous, i.e., a mix of non-ZWO cameras/focusers/filter wheels, or if you want maximal flexibility across brands. The Mini may limit you due to driver/support constraints.
• You need advanced/custom scripting, very complex automation, or run multiple heavy tasks (e.g., very large mosaics, heavy live-stacking) where a full PC might be more robust.
• Your power supply situation is marginal or you are using a lot of accessories drawing from the Mini’s 12 V outputs: you’ll need to ensure a good battery/power rig, otherwise you might face instability.

My verdict

If you said “Steve, you are biased about this piece of equipment”, I think that would be a fair challenge. I think the ASIair Mini has made my astrophotography real fun. It has stripped away complexity, clutter and laptops! A very capable, well-designed controller for deep-sky astrophotography, uncomplicated, portable simplicity and wireless control. I think it fits the bill for a first standard deep sky astro rig with an APS-C size camera, smaller refractor, decent mount or larger tracker. From my perspective, it is excellent value. Now, as a beginner, I know I will not be upgrading my kit until I have better understood and mastered some of the post editing skills, so I’ll be keeping the Mini for some time to come. A trusted co-pilot in my cosmic adventures.

On the other hand, if your ambitions are “enthusiast/pro” level with large sensors, many accessories and multiple brands, you might consider stepping up (e.g., to ASIAIR Plus/Pro or a dedicated mini-PC) so you don’t outgrow the device. And, don’t forget, you are locked into the ZWO ecosystem regarding other accessories such as focusers, filter wheels etc.

Bottom line – The ASIair Mini is a pocket-sized computer for your astro rig – smart, efficient and on the whole quietly brilliant. It won’t do everything, but what it does do, it does exceptionally well in my experience.

The ZWO ASIair Mini teamed with my Canon 800D, a RVO 32mm guide scope with ZWO 120mm mini guide cam

and below the rig mounted on my EQM-35-PRO mount 

This review gives some more details that you may find useful: https://www.cloudynights.com/articles/astro-gear-today/reviews/zwo%E2%80%99s-new-asiair-mini-reviewed-r4669/