Unihedron Sky Quality Meter with Lens (SQM-L)

  • An affordable meter for measuring sky brightness!
  • Unprecedented sensitivity in a handheld meter!
  • Measures the brightness of the night sky in magnitudes per square arcsecond.
  • Designed by Dr. Doug Welch and Anthony Tekatch.


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  • Regular price $134.95

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Unihedron Sky Quality Meter with Lens (SQM-L)

The Sky Quality Meter-L measures how clear the night or site is. Compare the sky brightness at different sites with measured results! If you're a CCD use, you can make a correlation between the Unihedron SQM-L reading and when the background reaches some ADC level.

How to Use the Sky Quality Meter-L

  • Keep track of the evolution of light pollution in your area.
  • Set planetarium dome illumination to mimic the skies you are likely to experience elsewhere in the city.
  • Monitor sky brightness through the night, night-to-night, and year-to-year.
  • Determine which nights are the greatest for finding the faintest of lights.
  • 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.

Features of the Sky Quality Meter-L

  • Receive audible signals while measurement is in progress.
  • The sky brightness measure is displayed in visual magnitudes per square arcsecond.
  • Its infrared blocking filter restricts measurement to its visual bandpass.
  • Temperature is measured in both Celsius and Fahrenheit.
  • The model number and serial number can be displayed with different button press sequences.
  • Receive precision readings at even the darkest sites.
  • Its power-saving features provide maximum battery life.
  • Reverse battery protection.

    Full List of Specifications for the Sky Quality Meter-L

    • The Half-Width Half Maximum (HWHM) of the angular sensitivity is ~10 degrees.
    • The Full-Width Half Maximum (FWHM) is then ~20 degrees.
    • The sensitivity to a point source ~19 degrees off-axis is a factor of 10 lower than on-axis. A point source ~20 degrees and ~40 degrees 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 inches
    • Maximum light sampling time: 80 seconds
    • Specifications are subject to change without notice.

    OPT Product Number: UH-SQM-L 



    Warranty1 Year Warranty
    Customer Reviews
    4.9 Based on 9 Reviews
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    Filter Reviews:
    United States United States
    Excellent product...

    I always wondered how dark the sky was where I live. The maps always said that I was living in a rural sky but now with this device, I was able to get a true reading on the Bortle scale of usually over 21.60...much darker than I realized. By measuring the sky before I pull out my telescope, I can get a very good preview of the night viewing. The sky quality meter has proven to be worth ever penny.

    Lei W.
    United States United States
    Works as expected

    easy to use, values fairly consistent.

    Helen P.
    United States
    Unihedron Sky Quality Meter with Lens (SQM-L)

    Excellent: I would definitely buy from you again.

    Danny G.
    United States
    SQM-L Very Good Product

    This was shipped promptly and received a couple of days later. It appears to be a very good unit, simple to use and appears to provide consistent readings. Not much more you can ask for.

    James S.
    United States
    Great Opportunity

    This device is easy to use and a great way to accurately determine sky conditions for planning targets for viewing at our public observatory.

    Doug O.
    United States
    SQM Review

    Great device, easy to operate, even came with batteries!