Unihedron SQM-L Sky Quality Meter with lens
 Unihedron SQM-L Sky Quality Meter with lensUnihedron SQM-L Sky Quality Meter with lens 

Unihedron SQM-L Sky Quality Meter with lens

  (4 Reviews)
✓ 2 year warranty


15x in stock shipped 1-2 working days

About this product

Model:  unihedron-sqm-l

Offers a more narrow field of view than the SQM.

An affordable meter for astronomers wanting to measure their sky brightness.

Measures the brightness of the night sky in magnitudes per square arcsecond. 

Unprecedented sensitivity in a handheld meter! 

Designed by Dr Doug Welch and Anthony Tekatch. 



  • Find out how good the night or site REALLY is.
  • Compare the sky brightness at different sites quantitatively.
  • Document the evolution of light pollution in your area.
  • Set planetarium dome illumination to mimic the skies people are likely to experience elsewhere in the city.
  • Monitor sky brightness through the night, night-to-night, and year-to-year.
  • Determine which nights show the greatest promise for finding the 'faintest fuzzies'!
  • Calibrate the effect of sky brightness on qualitative measures such as the Bortle Scale.
  • Investigate how sky brightness correlates with the solar cycle and month-to-month sunspot activity.
  • Help provide local ground truth for future sky brightness predictions. 
  • CCD users can make a correlation between the SQM reading and when the background reaches some ADC level.


  • Audible signal while measurement is in progress.
  • Sky brightness displayed in visual magnitudes per square arcsecond.
  • Infrared blocking filter restricts measurement to visual bandpass.
  • Temperature in both Celsius and Fahrenheit as well as model number and serial number can be displayed with different button press sequence.
  • Precision readings at even the darkest sites.
  • Power-saving features designed in for maximum battery life.
  • Reverse battery protection.
  • The Half Width Half Maximum (HWHM) of the angular sensitivity is ~10°. The Full Width Half Maximum (FWHM) is then ~20°. The sensitivity to a point source ~19° off-axis is a factor of 10 lower than on-axis. A point source ~20° and ~40° off-axis would register 3.0 and 5.0 magnitudes fainter, respectively. 
  • Operates from 9V battery (included).
  • Size 3.6 x 2.6 x 1.1 in.
  • Maximum light sampling time: 80 seconds.
  • Specifications are subject to change without notice.


SQM L Instruction Manual


Customer reviews

Average Rating (4 Reviews):  
Write a Review and share your opinions!

Rating (max 5):  
Sky Quality Meter
15 December 2022  | 

Compact and robust product that works well and is simple to use.I bought it to help me understand how my deep sky observations vary with sky conditions.Having a numerical value is really useful!

Rating (max 5):  
Unihedron SQM-L Sky Quality Meter with lens
20 January 2022  | 

Device arrived in a timely manner, by Royal Mail.
Device seems to work well, but have to wait for a new moon to get proper reading for my area.

Rating (max 5):  
Does what it says
07 February 2020  | 

Gives plausible readings every time. Darkest so far has been 23.05 Mag/arcsec2 in my unlit bedroom. Outdoors I get 15.93 with a streetlight on and 19.55 with it off. It really does need a clear sky on a moonless night to get proper readings, so I'm still waiting for some real results.

Rating (max 5):  
Unihedron meter
24 October 2018  | 

Bought the meter to confirm reading taken on an IPhone. Unfortunately the phone was close at 18.57. But intend using it to help pick new area to move house to. Too many years spent in poor Sky area blighted by ever increasing light pollution. The meter is very easy to use, but it is a shame that they do not produce a dual purpose meter capable of being used as a basic meter and also as a fixed system. I feel that it is daft and overly expensive, to have to buy two meters one for each purpose.


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