Unihedron SQM-LU-DL Sky Quality Meter with USB and Data Logging
 Unihedron SQM-LU-DL Sky Quality Meter with USB and Data LoggingUnihedron SQM-LU-DL Sky Quality Meter with USB and Data Logging 

Unihedron SQM-LU-DL Sky Quality Meter with USB and Data Logging

£319.00✓ 2 year warranty


3x in stock shipped 1-2 working days

About this product

Model:  unihedron-sqm-lu-dl-h
Part Number:  unihedron-sqm-lu-dl-h

A USB enabled data-logging light meter for night-time sky brightness monitoring!

An affordable meter for continual, connected or autonomous data-logging to measure sky brightness for astronomers and light pollution investigators.

The "Sky Quality Meter - LU-DL" (SQM-LU-DL) measures the brightness of the night sky in magnitudes per square arcsecond.

Designed by Dr. Doug Welch and Anthony Tekatch


  • Measuring the night sky brightness during remote biological field experiments.
  • 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 prediction with the Clear Sky Clock.
  • CCD users can make a correlation between the SQM reading and when the background reaches some ADC level.


  • Sky brightness reported 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-upgradeable firmware.
  • Open protocol document.


  • 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 5.5 x 2.6 x 1.1 in.
  • Maximum light sampling time: 80 seconds.
  • Minimum light sampling time: 1 seconds.
  • Specifications are subject to change without notice.

What's in the box

  • SQM-LU-DL Unit
  • SQM-LU-DL Users Manual
  • CD with PDF Manual & Example Software
  • 15ft USB Cable
  • Battery-to-USB Adapter & Battery Holder
  • Calibration Sheet - Indicated unit USB serial number and calibration values
  • Optional - Weatherproof Housing

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