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 

• 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.