An affordable meter for measuring sky brightness for astronomers! The "Sky Quality Meter - L" measures the brightness of the night sky in magnitudes per square arcsecond. Unprecedented sensitivity in a handheld meter! 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 prediction with the Clear Sky Clock.
• CCD users can make a correlation between the SQM reading and when the background reaches some ADC level.

Features:

• Audible signal while measurement is in progress.
• Sky brightness displayed in visual magnitudes per square arcsecond.
• Infrared blocking filter restricts measurement to visual bandpass.
• Temperature in both Celsius and Fahrenheit as well as model number and serial number can be displayed with different button press sequence.
• Precision readings at even the darkest sites.
• Power-saving features designed in for maximum battery life.
• Reverse battery protection.

• 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.
• Operates from 9V battery (included with courier shipments).
• Size 3.6 x 2.6 x 1.1 in. (92 x 67 x 28mm)
• Weight 0.31 lb (0.14 kg)
• Maximum light sampling time: 80 seconds.
• Specifications are subject to change without notice.

Unihedron supports the goals of the International Dark-Sky Association .

Details: PDF instruction sheet [FR] Frequently Asked Questions SQM mailing list SQM users links Magnitudes/arcsecond² to cd/m² converter Conversion Calculator - NELM (V) to MPSAS (B) systems by K. Fisher Database of users readings Twilight measurements with the SQM

Reports including the SQM: Night Sky Photometry with Sky Quality Meter by Pierantonio Cinzano. "Contributions of artificial lighting sources on light pollution in Hong Kong measured through a night sky brightness monitoring" article by Chun Shing Jason Pun, Chu Wing So, Wai Yan Leung, Chung Fai Wong.   Science direct  arxiv. Human Contrast Threshold and Astronomical Visibility paper by Andrew Crumey. Report on sky colour: Red is the new black; Chris Kyba and colleagues PDF. Documenting Local Night Sky Brightness report, Jennifer Birriel of MSU. Measure Night Sky Brightness at Various Zenith Angles report, Jennifer Birriel of MSU. "Night sky photometry and spectroscopy performed at the Vienna University Observatory" published in the "Journal of Quantitative Spectroscopy and Radiative Transfer" Science Direct  arXiv. "The night sky brightness at Potsdam-Babelsberg including overcast and moonlit conditions" published in the "Journal of Quantitative Spectroscopy and Radiative Transfer" Science Direct  arXiv. "Worldwide variations in artificial skyglow" by Christopher C. M. Kyba, Kai Pong Tong, and more. Published in Nature.com : Scientific Reports. "Intercomparisons of Nine Sky Brightness Detector" by Peter den Outer, Dorien Lolkema, Marty Haaima, Rene van der Hoff, Henk Spoelstra, and Wim Schmidt. Published in 2014 The National Center for Biotechnology Information. Calibration of SQM-L photometers for the NixNox project, Zamorano Calvo, Jaime and Munoz Marín, Victor Manuel (2010), eprints.ucm.es/12262/ Zamorano, Jaime y Munoz Marin, Victor Manuel (2010), Calibration of SQM-L photometers for the NixNox project. [ LICA report; no. #01], eprints.ucm.es/12262/ Zamorano, Jaime & Ruiz Carmona, Roque (2013), Sky Quality Meter cross-calibration for the NixNox project. [ LICA report; no. #03], eprints.ucm.es/18015/ Nievas Rosillo, Miguel & Zamorano, Jaime (2014), *PySQM the UCM open source software to read, plot and store data from SQM photometers*, eprints.ucm.es/25900/ Zamorano, Jaime, Sanchez de Miguel, Alejandro, Martinez Delgado, David & Alfaro Navarro, Emilio (2011) Proyecto NixNox disfrutando de los cielos estrellados de Espana. Astronomia (142). pp. 36-42. ISSN 1699-7751, eprints.ucm.es/24185/ Zamorano, Jaime, Sanchez de Miguel, Alejandro, Nievas Rosillo, Miguel & Tapia Ayuga, Carlos (2014) NixNox procedure to build Night Sky Brightness maps from SQM photometers observations., eprints.ucm.es/26982/ "Initial Irish light pollution measurements and a new Sky Quality Meter-based data logger" by B Espey, PhDa,b, and J McCauley, MSca. Published on February 2014 vol. 46 no. 1 67-77. Lighting Research and Technology. Excursion to Dark Sky Preserves in Canada 2015 by Andreas Hänel. SQM cross-calibration procedure by the BuioMetria Partecipativa team, 2011 PDF. Poster on the BuioMetria Partecipativa project presented at the IAU 2012 General Assembly in Beijing. Dark box for low-light-level measurements of a camera using an SQM-LU PDF by Peter Hiscocks. Integrating Sphere for Luminance Calibration PDF by Peter Hiscocks. Birds advance their dawn chorus near airports Report uses SQM to assist in determining bird chorus timing due to other effects. By Diego Gil et al. Comprehensive list of SQM related reports found on 2017-02-17. Quantifying and Monitoring Darkness over the RAO (Rothney Astrophysical Observatory) By Phil Langill and Benjamin George. Temperature Stability of the Sky Quality Meter By by Sabrina Schnitt, Thomas Ruhtz, Jürgen Fischer, Franz Hölker, Christopher Kyba. CoSQM - a color hack to the SQM-LE for Light At Night Sensing by Martin Aube Impact of Space Weather on the Natural Night Sky Grauer, A. D., Grauer, P.A., Davies,N. and Davies, G. PASP Volume 131, Number 1005, November 2019 Central Oregon Skyglow Measurement Network by Bill Kowalik and Mike McKeag. This report includes long term measurements and annotations plots of data logged Sky Quality Meter readings using the SQM-LU-DL in dark sky areas. Updated August 16, 2022 Measurements of sky brightness at Bosscha Observatory, Indonesia by D. Herdiwijaya and others. This report includes long-term light pollution studies using SQM meters from 2011. Linking solar minimum, space weather, and night sky brightness Albert D. Grauer, Patricia A. Grauer, Nature Scientific Reports (2021) 11:23893. Video: Creating a Dark Sky Place - Mayo Dark Sky Park Guests for Heritage Week 2021 Anthony Tekatch answers questions about the Sky Quality Meter, specifically setting up the data-logging model. Video: Doug Welch discusses The Life and Times of the Sky Quality Meter (SQM) - Feb 21, 2022 Allsky and SQM movie (overcast night) , Allsky and SQM movie (clear night) by Bill Kowalik Drivers of artificial light at night variability in urban, rural and remote areas by Luciano Massetti NSKY-CD: A System for Cloud Detection Based on Night Sky Brightness and Sky Temperature by Luciano Massetti, Alessandro Materassi and Francesco Sabatini/li> Monitoring Light Pollution with an Unmanned Aerial Vehicle (UAV): A Case Study Comparing RGB Images and Night Ground Brightness by Luciano Massetti 1, Marco Paterni 2, and Silvia Merlino Sky Brightness and Cloud Cover at Several Locations Across Missouri by Vayujeet Gokhale and Andrew Gentry of Truman State University & University of New Mexico Light pollution maps / databases: Unihedron Database of Sky Quality Meter readings from around the world. Globe at Night : Maps and Data. Light Pollution Map by Jurij Stare which displays light radiance from NOAA and SQM data from the Unihedron reading database. See this paper for details on map modelling: The first World Atlas of the artificial night sky brightness Database of readings from Turkey with map. SQM-Network is a free network of connected SQM meters from around the world. SQM network in Southern part of Switzerland Loss of the Night - Easily accessible web application. A night sky brightness network with data obtained with fixed SQM photometers of the Spanish Light Pollution Research Network. guaix.fis.ucm.es/splpr/SQM-REECL Regional SQM network in the Northern part of the Netherlands, managed by Groningen University, Kapteyn Astronomical Institute and ScienceLinX: www.washetdonker.nl. We expect the extension of the network early 2020. All-sky Light Pollution Survey (ALPS). ALPS is a Polish network of automatic stations Useful Light pollution links: IDA: How To Conduct A Sky Quality Survey Downloads or users contributions Light pollution report by Richard Berry Radiometry and photometry in astronomy By Paul Schlyter Notes from sci.astro.amateur Surface Brightness by Tony Flanders The Bortle Dark-Sky Scale by John E. Bortle Outdoor Lighting and Crime by Dr. Barry Clark Part 1 Part 2 Extra "A Rationale for the mandatory limitation of outdoor lighting" by Barry A. J. Clark, PhD [revised Feb 28, 2008] GLOBE at Night. What does your nighttime sky look like? Applet Starry Night Lights : Night Sky Friendly Outdoor Lighting Products SkippySky Astro-Weather Forecast SKYGLOW : Light pollution & the UK's changing skies International Astronomical Union : Cosmic Light Programme Addressing Light Pollution Using Dark Sky Approved Lighting to Reduce Light Pollution The dark side of light: how artificial lighting is harming the natural world : Nature journal article What Is The Bortle Scale? Light Pollution Classes Explained Light Pollution Platform by Dark Sky Lab

SQM tripod adaptor option
SQM example	SQM-L example	SQM-LE example	SQM-LU-DL example	This adaptor kit was designed to fit the SQM, SQM,L,LU,LE,LR,DL. The battery compartments in the handhelds meters is accessible with the adaptor in place. The adaptor screws into the back of the meter and allows the meter to be mounted on a tripod with a 1/4-20 thread. The kit includes one tripod adaptor, 3D-printed black or white plastic adaptor, and two longer screws (to replace two short screws already in the meter). 3D part view	SQM-x-TA Kit $20USD