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Connected meters (SQM-LE/LU/LR/DL) / Re: SQM-LU Detection Cutoff Angle
« Last post by MgcJim on November 03, 2022, 01:25:14 am »
Excellent.  That's exactly what I was looking for.
Connected meters (SQM-LE/LU/LR/DL) / Re: SQM-LU Detection Cutoff Angle
« Last post by admin on November 02, 2022, 12:56:19 am »
The following plot shows the response of the meters at various angles.

Connected meters (SQM-LE/LU/LR/DL) / SQM-LU Detection Cutoff Angle
« Last post by MgcJim on November 01, 2022, 09:34:19 pm »
With the SQM pointed vertically, is there an effective zenith angle cutoff for measurements?  I suspect it does not measure light at a zenith angle of 90 deg.  Perhaps there is a "detection drop off" function?  My concern is the location I want to mount the meter in is not taller than the observatory that is closeby.

Weatherproofing / Customer made weatherproof housing
« Last post by admin on April 18, 2022, 11:45:57 am »
One of our customers made his own weatherproof housing for his personal observatory to hold the SQM-LU using the cap from our weatherproof housing.

The advantage here is that the cover is protected with another removable cover since he is only taking measurements when using the telescope.

Here are some photos:

Connected meters (SQM-LE/LU/LR/DL) / Important update to SQM Reader Pro 3
« Last post by knightware on March 18, 2021, 01:11:51 pm »
Knightware is pleased to announce the release of a significant update to SQM Reader Pro 3. The update is available at no charge to licensed users of SQM Reader Pro 3.

An important feature was added in this update: support for sending readings to the Globe at Night Sky Brightness Monitoring Network (GaN-MN). Users need to register their SQM installations with the GaN-MN for data to be accepted.

The update also includes enhanced support for high resolution monitors. This will be most effective on Windows 8.1 and 10 but also works on Windows 7 and 8.0.

You can learn about SQM Reader Pro 3 software at
You can learn about GaN-MN at
You can register your SQM installation by contacting
or for users in China.

Phyllis Lang
Author, SQM Reader Pro
SQM-LU / New Android app for SQM-LU
« Last post by mdborland on March 11, 2021, 06:27:11 pm »
I didn't have any luck with the SQMDroid application and besides I was not happy about having to sideload an application onto my phone, since that  bypasses Google malware scanning. So, I brushed off my Java coding skills and wrote my own app. It's available on the Google store for a nominal fee.

This app allows reading and logging sky quality data from the Unihedron(TM) SQM-LU using an Android phone. You need a USB OTG cable to allow plugging the SQM-LU into your phone.

The app not only reads the sky quality and device temperature, but also optionally the GPS coordinates if location permission is granted. If file permissions are granted, it will log the data to a CSV file. The app also uses the sensors on your phone to compute the altitude and azimuth; if you hold the SQM back-to-back with your phone, this should tell you where the SQM is pointing.

I was going to give away, but my wife hates it when I do that. In any case, for $0.99, perhaps some of you are interested.

I suppose it will work with the SQM-LU-DL as well, but since I don't have one of those I couldn't check.

General Discussion / Re: Reports
« Last post by admin on September 01, 2020, 12:54:40 pm »
This report includes long-term light pollution studies using SQM meters from 2011:

Measurements of sky brightness at Bosscha Observatory, Indonesia by D. Herdiwijaya and others.
Connected meters (SQM-LE/LU/LR/DL) / Re: GPS integration
« Last post by admin on January 29, 2020, 10:09:31 pm »
Some computers reassign the communications port at power up or re-connection, so to ensure that the UDM can recognize both the SQM and the GPS, please follow these steps:
  • Disconnect the SQM and GPS from computer before powering up.
  • Power up the computer.
  • Start up UDM.
  • Connect the SQM and ensure you get a reading.
  • Disable the GPS connectivity from the log continuous tab.
  • Connect the GPS, and under the Log Continuous GPS tab ensure you are getting GPS location data.
  • Carry on from there.
General Discussion / SQMs strapped to a plane
« Last post by admin on December 31, 2019, 02:45:11 pm »
Here is an interesting report by Phil Langill using two SQM-LU meters strapped to the side of an airplane:

 Measuring and Monitoring Darkness at 10,000 feet (PDF)
 Measuring a darkness baseline for new developments near the Rothney Astrophysical Observatory
 Poster  presented at the Starlight Conference in Lake Tekapo NZ back in October 2019
 By Phil Langill – RAO Director, University of Calgary

General Discussion / [PAPER] Impact of Space Weather on the Natural Night Sky
« Last post by admin on November 06, 2019, 03:45:29 pm »
Here is an interesting paper on the Impact of Space Weather on the Natural Night Sky by Albert Grauer and colleagues using readings from the Unihedron SQM which will be presented at the IDA Annual General Meeting in Tucson Arizona on Saturday November 9 2019.

The abstract:
  In 2018, Solar Cycle 24 entered a deep solar minimum. During this period, we collected night sky brightness data at Cosmic Campground International Dark Sky Sanctuary (CCIDSS) in the USA (2018 September 4–2019 January 4) and at Aotea/Great Barrier Island International Dark Sky Sanctuary (AGBIIDSS) in New Zealand (2018 March 26–August 31. These sites have artificial-light-pollution-free natural night skies. The equipment employed are identical Unihedron SQM-LU-DL meters, used as single-channel differential photometers, to scan the sky as Earth rotates on its axis. We have developed new analysis techniques which select those data points which are uninfluenced by Sun, Moon, or clouds to follow brightness changes at selected points on the celestial sphere and to measure the brightness of the airglow above its quiescent level. The 2018 natural night sky was measured to −2change in brightness by approximately 0.9 mag arcsec at both locations. Preliminary results indicate the modulations of the light curves (brightness versus R.A.) we observed are related in complex ways to elements of space weather conditions in the near-Earth environment. In particular, episodes of increased night sky brightness are observed to be contemporaneous with geomagnetic activity, increases in mean solar wind speed, and some solar proton/electron fluence events. Charged particles in the solar wind take days to reach near-Earth environment after a coronal hole is observed to be facing in our direction. Use of this information could make it possible to predict increases in Earth’s natural night sky brightness several days in advance. What we have learned during this solar minimum leads us to search for other solar driven changes in night sky brightness as the Sun begins to move into solar maximum conditions.

You can read the paper here:

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