Unihedron SQM-LU Sky Quality Meter with USB
 Unihedron SQM-LU Sky Quality Meter with USBUnihedron SQM-LU Sky Quality Meter with USB 

Unihedron SQM-LU Sky Quality Meter with USB

£210.00✓ 2 year warranty


3x in stock shipped 1-2 working days

About this product

Model:  unihedron-sqm-lu

A USB SQM for night-time sky brightness monitoring

An affordable meter for continual, connected measuring of sky brightness for astronomers.

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

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.


  • Sky brightness displayed in visual magnitudes per square arcsecond.
  • Infrared blocking filter restricts measurement to visual bandpass.
  • Sensor temperature, model number and serial number are provided.
  • Precision readings at even the darkest sites.
  • Field-upgradable firmware.
  • USB connectivity
  • Included applications for reading data in Perl.
  • 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. 
  • Size 3.6 x 2.6 x 1.1 in.
  • Maximum light sampling time: 80 seconds.
  • Minimum light sampling time: 1 second.
  • Specifications are subject to change without notice.


  • SQM-LU unit
  • SQM-LU users manual
  • CD with PDF manual and example software
  • 15ft USB cable
  • Calibration sheet indicates unit USB serial number and calibration values


SQM LU Instruction Manual


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