ZWO ASI120MM Mini review: a light, simple guide camera
Where does it rank on our leaderboard
| Rank | Camera | Stars for Your Buck | Recorded UK price |
|---|---|---|---|
| 1 | SVBONY SV705C | 93 out of 100 | £229 |
| 2 | SVBONY SC571CC | 90 out of 100 | £1,029 |
| 7 | ZWO ASI2600MM Air | 84 out of 100 | £2,499 |
| 14 | Player One Apollo-M MAX | 76 out of 100 | £485 |
| 17 | ZWO ASI120MM | 75 out of 100 | £199 |
| 20 | ASI 4400MC | 72 out of 100 | £3,299 |
| 24 | ZWO ASI533MM | 66 out of 100 | £999 |
| 28 | ZWO ASI183MC | 38 out of 100 | £549 |
| 29 | Nikon COOLPIX P1000 | 32 out of 100 | £787 |
Contents
- 01 Where does it rank on our leaderboard
- 02 Specifications and features
- 03 In the hand
- 04 The rig on the mount
- 05 What is it for
- 06 Watch the review
- 07 Should you buy it?
- 08 Questions and more about this review
In 30 seconds
Stars for Your Buck 75/100
Reviewed 30 Aug 2025 Updated 24 Sep 2026
- Rank
- #17 of 29 cameras
- Verdict
- Damon recommends
Written by Damon Scotting 3 min read
Buy it if
- you are adding autoguiding to a small refractor rig and want the lightest, simplest guide camera
- your guide scope takes a 1.25 inch camera and your rig runs from a ZWO ASIAIR
Skip it if
- you guide under bright skies or with short exposures: the ASI220MM's newer sensor sees more stars
- your imaging camera already carries a guide sensor, as the ASI585MC Air and ASI2600MC Duo do
Specifications and features
Against the guide cameras I have reviewed
Compare with
| ZWO ASI120MM reviewed #17 of 29 | ZWO ASI220MM #23 of 29 | |
|---|---|---|
| Recorded UK price | £199 | £299 |
| Stars for Your Buck | 75/100 | 67/100 |
| Sensor | AR0130CS, mono CMOS | SC2210, mono CMOS |
| Format | 1/3 inch, 4.8 x 3.6 mm | 1/1.8 inch, 7.68 x 4.32 mm |
| Colour or mono | Mono | Mono |
| Resolution | 1280 x 960, 1.2 MP | 1920 x 1080, 2.1 MP |
| Pixel size | 3.75 um | 4 um |
| Cooling | Uncooled | Uncooled |
| Read noise | 4.0 e- | 0.6 to 3.2 e- |
| Full well | 13 ke- | 8.78 ke- |
| ADC | 12-bit | 12-bit |
| Weight | 60 g | 60 g |
| Back focus | 8.5 mm | 8.5 mm or 12.5 mm |
| Interface | USB 2.0 Type-C, ST-4 guide port | USB 2.0 Type-C, ST-4 guide port |
| In the box | Camera, 1.25 inch cap, 0.5 m and 2 m USB 2.0 cables, 2 m ST-4 cable, M28.5 to CS adapter, 1.25 inch extender, quick guide | Camera, 1.25 inch cover, 1.25 inch extender, M28.5 to CS adapter, ST-4 cable, 0.5 m and 2 m USB 2.0 Type-C cables, quick guide |
In the hand
At the back of the 50 mm guide scope
Riding above the RedCat 51
Ready to guide at dusk
On the TeSeek 11 at dusk
The rig on the mount
On the TeSeek 11, then on six other mounts
What is it for
Three things it is for
Longer exposures behind a filter
I needed to add a guide scope and camera to increase the lengths of my exposures, because using intense filters like this really limits the amount of total light coming through, so longer exposures are a must.
Andromeda in the guide frame
You can actually see it showing up here on the left through the guide camera as this little faint fuzzy blob.
A small, portable rig
An SVBONY 30 mm guide scope and an ASI120 monochrome guide camera, all attached to the tiny Hope D60 telescope: it's a very portable and powerful setup.
Watch the review
I tried a £299 Telescope mount?! Surprisingly GOOD! (TeSeek 11 mount) · published 30 August 2025 · 8:14 · Watch on YouTube · 24,851 views, 861 likes on 2 Oct 2026
Jump to
- 2:34 GOAT setup
- 2:58 The rig: RedCat 51, ASI533MM Pro, 50 mm guide scope and the ASI120MM
- 3:33 Guiding results
- 4:35 Seven minutes on the North America Nebula
- 5:13 Andromeda in the guide camera
- 5:51 The Heart Nebula
- 6:17 The whole night's guiding
- 6:46 Improvements
Transcript of the review video 820 words · 7 chapters · searchable
Press a time stamp to play from there.
2:41 GOAT setup
2:41 Now to put it to the test, I've decided to give it a baptism of fire and mount my narrowband guiding telescope setup. 2:46 Who would have thought baptism of fire meant RedCat 51 telescope. 2:52 Overall this telescope rig weighs 4.11kg which isn't too far off the max recommended payload. 2:58 I'm using an ASI533 monochrome Pro with a 7 x 2 inch ZWO filter wheel and a RedCat 51 f/3.5 with a 50mm guide scope and ASI120 monochrome guiding camera, all connected to an ASIAIR that's sitting awkwardly on a little tray that keeps the tripod legs at a fixed distance apart.
2:58 The rig: RedCat 51, ASI533MM Pro, 50 mm guide scope and the ASI120MM
3:20 Alright, time for the moment of truth, how well does it guide? 3:23 As you can probably notice in the background, it's a full moon tonight and I've got my beloved fairy lights cranked all the way up to 100%, simulating the brightness of 10 billion suns in my garden. 3:31 All because I just love light pollution, I love the hustle of being an astrophotographer who doesn't benefit from Bortle 1 skies.
3:33 Guiding results
3:40 In fact last night I asked my landlord to increase my rent. 3:40 That's how much I believe in my grind. 3:45 So with that in mind I roughly polar aligned my telescope rig to Polaris using the built-in laser and then told it to go find the North America Nebula and start guiding. 3:54 And it did so without a fuss. 3:54 What we're hoping for here in terms of RMS with this mount is less than a total of 3.00. 3:58 If it's less than 3 then I'd class it as you get what you pay for. 4:03 If it's less than 2 then I'd say that's good value for money. 4:08 And if it's consistently less than one, then I'm going to buy about 10 of these and donate them to as many astronomical societies here in the UK as possible. 4:15 I've sped things up throughout the guiding process so that you can see how well it does over the course of an hour whilst guiding during a full moon, pointed at multiple different locations in our night sky. 4:24 I've also snapped a quick 30 second exposure here to showcase the star shapes. 4:28 I find this a little harder to assess in monochrome. 4:30 When shooting in colour it feels like it's easier to tell if something's bad or good, but generally these star shapes look really good.
4:35 Seven minutes on the North America Nebula
4:36 So here's a 10x sped up view of 7 minutes worth of guiding when looking almost straight up at the North America Nebula during a full moon. 4:41 Overall, very good readings. 4:41 I think the highest RMS value reached was 1.24. 4:47 I'm pretty sure these are the default ASIAIR guiding settings, so you could hyper-tune them to specifically suit the pulse readings from this mount to improve it even further. 4:57 But straight out of the box, this is a very good start. 4:57 However, the North America Nebula is directly overhead and easy to see. 5:02 I'm now going to slew the mount towards a more difficult target, the Andromeda Galaxy. 5:07 It's only more difficult because there's less nearby stars and it's lower in the horizon, but this is 13 minutes worth of guiding whilst pointed at M31.
5:13 Andromeda in the guide camera
5:17 You can actually see it showing up here on the left through the guide camera as this little faint fuzzy blob. 5:21 And once again I think these are some semi-decent numbers. 5:26 I was moving around a lot whilst guiding this time but I don't think that's had too strong of an influence on it. 5:30 This was during the peak of the Perseids meteor shower so I did briefly turn off the fairy lights to try and get a better look at them. 5:33 But it's never easy to spot meteors during a full moon, let's face it. 5:40 The stars once again seemed fine, the image looks rubbish no thanks to the moon, and there was one spot where I thought I could see the stars trailing indicating poor guiding for a 300 second exposure, but it was actually a binary star.
5:51 The Heart Nebula
5:53 To finish things off I slewed over to the Heart Nebula, which will have been arguably one of the most difficult areas to guide tonight. 5:56 Its first attempt to centre the object in its field of view was almost perfect, and it only took 2 in total before it had it perfectly aligned. 6:05 I've sped the recording of this guiding video up to 40 times because I think you get the gist, although if you're a hyper analytical astrophotographer feel free to change the playback of this video to 0.25 times for a more thorough viewing experience.
6:17 The whole night's guiding
6:18 Throughout the entire night, the mount never went above 2.00 in terms of guiding, and I think on average its RMS would have been just about 1. 6:22 Which according to the product description on AliExpress is not too far off that estimation of 0.6 to 1, supposedly using a 130 mm reflector telescope.
Check out more videos on the ZWO ASI120MM
I Captured a Gigapixel Orion Mosaic! - ASI 4400MC Review
30 Jan 2026
What YOU can SEE with a £2000 "USED" Telescope setup?!
12 Jul 2025
Should you buy it?
75/100 Stars for Your Buck
Pros
- Behind a 50 mm guide scope it picked up the Andromeda Galaxy as a faint smudge in its guide frame
- 60 g and 36 mm across: it slides into a 1.25 inch guide scope and barely adds to the payload
- On the TeSeek 11 with a RedCat 51 and a 50 mm guide scope, the highest RMS in seven minutes on the North America Nebula under a full Moon was 1.24 arcsec
- An ST-4 guide port as well as USB 2.0 Type-C, and cables for both in the box
Cons
- The SC2210 guide sensor in the ASI220MM and the ASI585MC Air is larger (1/1.8 inch against 1/3 inch) with far less read noise (0.6 to 3.2 e- against 4.0 e-)
- A 1/3 inch, 1.2 MP sensor, 4.8 x 3.6 mm: a small field in which to find guide stars
- USB 2.0 and 35 frames a second at full resolution: a guide camera first, not a planetary camera
The ASI120MM Mini is the small guide camera on my light rigs, from the RedCat 51 on the TeSeek 11 to the Hope D60 on the JUWEI-14. Newer guide sensors are a huge improvement on it, so it is the budget choice rather than the best one.
Who the ASI120MM Mini is for
First autoguiding rig on a small refractor
Buy
At the back of a 30 or 50 mm guide scope it is the lightest way to start guiding.
ZWO ASIAIR owner
Buy
It is ZWO's own guide camera, so the ASIAIR drives it with the rest of the rig.
Imager under bright suburban skies
Skip
My recommendation is the ZWO ASI220MM: its newer, larger sensor finds fainter guide stars.
Buyer of an imaging camera with a guide sensor built in
Skip
The ZWO ASI585MC Air and ASI2600MC Duo guide from their own second sensor, so no separate guide camera is needed.
Planetary imager
Skip
A 1.2 MP sensor over USB 2.0 is a guide camera first; an IMX585 camera such as the Player One Uranus-C suits planets.
Three alternatives I have reviewed
- ZWO ASI220MM ZWO's newer guide camera: a larger, more sensitive SC2210 sensor 67/100 £299 Read the review
- ZWO ASI585MC Air An IMX585 imaging camera with the SC2210 guide sensor built in 89/100 £799 Read the review
- SVBONY SV705C An uncooled IMX585 camera with an ST-4 port that can image or guide 93/100 £229 Read the review
Questions and more about this review
Reviewed by
Damon Scotting
The Telescope Man Verified
BSc (Hons) Physics with Astrophysics and Cosmology, Loughborough University PGCE / QTS, University of Nottingham
About Damon About Damon Damon Scotting is The Telescope Man. He holds a BSc (Hons) in Physics with Astrophysics and Cosmology from Loughborough University and a PGCE with QTS from the University of Nottingham, and taught physics in secondary schools before becoming an astronomy creator. He is a contributing writer for BBC Sky at Night Magazine and the author of 42 Wonders of Our Night Sky, and his photograph of the galaxy M100 with the dwarf planet Ceres was Highly Commended in the Astronomy Photographer of the Year 2024 competition run by Royal Observatory Greenwich. He has appeared on the BBC's Blue Peter. More than 750,000 people follow his astronomy channels on YouTube, Instagram and TikTok, and he has reviewed more than 140 telescopes, mounts, cameras, filters and accessories hands-on for this site. More about Damon · How I test · Damon's book
I review all kinds of gear: most of it I buy, some is gifted and some is loaned, and all of it is reviewed the same way. How this site is funded
Six questions, answered
Questions about the ZWO ASI120MM
Reviewed 30 August 2025 ·Updated 24 September 2026
I review all kinds of gear. Most of it I buy, some is gifted and some is loaned, and all of it is reviewed the same way: no company sees or approves a review before it is published. Shop links marked Ad are affiliate links: I earn a commission when you buy through them, at no extra cost to you. How this site is funded
- Is the ZWO ASI120MM the same as the ASI120MM Mini? The ASI120MM sold today is the ASI120MM Mini: a 1.25 inch, 60 g mono guide camera with USB 2.0 Type-C and an ST-4 port. ZWO's store lists it under its mini cameras; the older USB 3.0 ASI120MM-S body has no page there. The specifications and the comparison table ↓
- How well does the ASI120MM Mini guide? On the TeSeek 11, with a RedCat 51, an ASI533MM Pro, a filter wheel and a 50 mm guide scope, the highest RMS in seven minutes on the North America Nebula during a full Moon was 1.24 arcsec, and the mount averaged about one arcsec through the night. Watch the review ↓
- Which guide scope suits the ASI120MM Mini? I have used it on a 50 mm guide scope over the RedCat 51 and on the SVBONY 30 mm guide scope over the ToupTek Hope D60. What is it for ↓
- Should I buy the ASI120MM Mini or the ASI220MM? The ASI220MM's SC2210 is larger (1/1.8 inch, 1920 x 1080 at 4 um) and newer; the ASI120MM Mini is £199 against the ASI220MM's £299 at First Light Optics. The specifications and the comparison table ↓
- Where can I buy the ZWO ASI120MM Mini? The prices I recorded: £199 at First Light Optics (UK), in stock; $199 at Agena Astro (US), in stock; $199 at ZWO store (Global), in stock. A record, not a live price The verdict, the readers and the sellers ↓
- What have I not tested on the ASI120MM Mini? I have not measured the ASI120MM Mini's read noise or sensitivity, and I have not compared it with another guide camera on the same night.