Unihedron SQM-L review: a sky quality meter with a lens
Where does it rank on our leaderboard
| Rank | Accessory | Stars for Your Buck | Recorded UK price |
|---|---|---|---|
| 1 | GEMINI EAF | 100 out of 100 | £42 |
| 2 | Generic Dew Heater | 93 out of 100 | £9 |
| 5 | Generic 0.63x Reducer | 88 out of 100 | £54 |
| 20 | ToupTek EAF | 75 out of 100 | £170 |
| 31 | ZWO TC40 Tripod | 60 out of 100 | £342 |
| 38 | Celestron 3x Barlow | 45 out of 100 | £145 |
| 44 | Unihedron SQM-L Sky Quality Meter with Lens | 32 out of 100 | £149 |
| 45 | SKY ROVER 2x54 Binoculars | 28 out of 100 | £139 |
| 46 | 365 Solar Telescope Cover | 5 out of 100 | £73 |
Contents
- 01 Where does it rank on our leaderboard
- 02 Specifications and features
- 03 In my words
- 04 Should you buy it?
- 05 Questions and more about this review
In 30 seconds
Stars for Your Buck 32/100
Written 25 Sep 2026 Updated 25 Sep 2026
- Rank
- #44 of 46 accessories
- Verdict
- With reservations
Written by Damon Scotting 2 min read
Buy it if
- You want to compare the darkness of your garden and a dark site in numbers, not impressions.
- You want to follow the light pollution over your site from season to season.
Skip it if
- You want to judge seeing or transparency: it measures sky brightness only.
- You want readings logged through the night on their own: this is a handheld meter, one reading per press of its button.
The SQM-L puts a number on how dark your sky is: it reads the sky overhead in magnitudes per square arcsecond through a lens that narrows its view to about 20 degrees.
Specifications and features
| Unihedron SQM-L reviewed #44 of 46 | |
|---|---|
| Recorded UK price | £149 |
| Measures | Sky brightness in magnitudes per square arcsecond |
| Field of view | About 20 degrees (full width at half maximum) |
| Filter | Infrared blocking, visual band |
| Longest reading | 80 seconds |
| Also shows | Temperature in Celsius and Fahrenheit, the model and serial number |
| Power | One 9 V battery |
| Size | 92 x 67 x 28 mm |
| Weight | 140 g |
In my words
“A handy piece of kit that gives you an insight into the quality of your night sky. It's very limited in its functions and features, and certainly very expensive for what it offers. It's a nice little gizmo to have, but at the cost, I'm not sure it's the smartest investment out there.”
From my dictated take
Should you buy it?
32/100 Stars for Your Buck
Pros
- It reads sky brightness in magnitudes per square arcsecond, so readings compare between sites.
- The lens narrows its view to about 20 degrees, so lights low on the horizon count for far less.
- An infrared blocking filter keeps the reading to the visual band.
- It shows the temperature too, in Celsius and Fahrenheit.
- Pocket sized at 92 x 67 x 28 mm and 140 g, on one 9 V battery.
Cons
- It measures sky brightness only, not seeing or transparency.
- A reading can take up to 80 seconds.
- One reading per press of its button: for readings logged through the night, Unihedron makes the SQM-LU-DL.
A pocket meter that puts a number on how dark your sky is, one you can compare between sites and seasons.
Three alternatives
- Weather Station Reads the wind, humidity and rain at your site, which a sky meter cannot 88/100 £225 Read the review
- Telescope Cover Keeps the rain and dew off a telescope left outside between clear nights 90/100 £25 Read the review
- Generic Dew Heater Keeps dew off the optics on the clear, damp nights worth measuring 93/100 £9 Read the recommendation
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
Four questions, answered
Questions about the Unihedron SQM-L
Written 25 September 2026 ·Updated 25 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
- What does the L in SQM-L mean? The lens. It narrows the meter's view to about 20 degrees across at half sensitivity, and a light 20 degrees off the axis reads 3 magnitudes fainter than it would straight ahead. The specifications ↓
- Does the SQM-L measure seeing? No. It measures the brightness of the night sky in magnitudes per square arcsecond; seeing and transparency need other tools. The specifications ↓
- How long does a reading take? Up to 80 seconds, the longest sampling time Unihedron gives; the meter beeps while it measures. The specifications ↓
- Where can I buy the Unihedron SQM-L? The prices I recorded: £149 at First Light Optics (UK), in stock; $155 at Unihedron (Global), in stock. A record, not a live price The verdict, the readers and the sellers ↓