Unihedron Sky Quality Meter - LU-DL (SQM-LU-DL)

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

Uses: 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.

SQM-LU-DL control panel

Features:

• 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.
• All the features of our SQM-LU (USB model) plus Data logging capabilities.
• 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. Annotated FOV spec.

Comparison chart

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• Size 5.5 x 2.6 x 1.1 in.
• Maximum light sampling time: 80 seconds.
• Minimum light sampling time: 1 seconds.
• Powered by external battery pack (included) for field data logging, or USB data cable for computer powered data logging using UDM, or 5V USB "phone" charger for mains powered data logging (see charger requirements here).
• Recording memory capacity: 1048576 records total.
• Specifications are subject to change without notice.

Weatherproof Housing

This housing design is made to protect the SQM-LE/LU from normal outdoor conditions including weather and insects.

Features:

• White surfaces reflect the hot summer sunshine.
• Opening on bottom to allow moisture to escape.
• Glass top to prevent scratching when removing ice.
• Raised glass surface to prevent dirt and leaves from collecting.
• Small glass opening to minimize internal heating due to the Sun.
• Cable opening at bottom sealed with open-cell (breathable) foam prevents insects from entering.
• Marine silicone seal rated for outdoor use.
• Silicone seal around glass extends beyond glass-plastic interface to prevent ice from building in crevices.
• Hose clamps for easy mounting to pole.
• Staples for easy mounting to wood surface.

Details:

• Diagram of all SQM meters that fit into housing (PDF)
• Photos
• Glass versions (PDF)
• SQM-LE wiring layout inside housing.

What you get:

• Housing with removable top cap. 8.8 x 18.7cm, 360g.
• Two adjustable clamps.
• Two staples for mounting to wood.
• Instruction sheet.
• An optional PoE (Linksys WAPPOE-5V or D-Link DWL-P200 or TL-POE200) for extended length SQM-LE installations.

What you get (meter only):

• SQM-LU-DL unit
• USB flash drive containing the users manual, operation software (UDM), and example software. This can also be found online.
• 15ft USB cable
• Battery-to-USB adapter with 6 AA cells and battery holder
• Calibration sheet indicates unit USB serial number, and calibration values

What you get (with housing):

SQM-LU-DL unit USB flash drive containing the users manual, operation software (UDM), and example software. This can also be found online. 15ft USB cable Battery-to-USB adapter with 6 AA cells and battery holder Calibration sheet indicates unit USB serial number, and calibration values Weatherproof housing

Warranty: Unihedron Warranty