Recent Posts

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General Discussion / Twilight measurements with the SQM
« Last post by admin on September 15, 2014, 01:17:28 am »
We've had some queries about using the SQM products for measuring light during twilight.
The SQM meters are mainly intended for night time readings and will saturate in daylight. However, with the addition of a Neutral Density (ND) filter over the light sensor, the range of readings can be shifted to be useful in brighter settings.

Here is a page dedicated to some of those questions and applications:
Connected meters (SQM-LE/LU/LR/DL) / FTDI driver installation problems
« Last post by admin on September 03, 2014, 03:46:48 pm »
For some strange reason a recent problem with the installation of the FTDI USB driver for Windows has cropped up. The problem may something to do with cancelling the automatic installation of the FTDI USB VCP driver when connecting a new SQM USB device.

The Windows registry saves old versions and old COM port assignments, and can only be cleaned up with a custom utility provided by the driver manufacturer (FTDI). Here are the steps to solve that problem:

Install this FTDI "CDM Uninstaller" utility:

The detailed instructions for its operation are here:

Here is a summary of the instructions:
  • Remove/unplug the SQM-LU device
  • Start up the CDM uninstaller program
  • Press - Add
  • Press - Remove devices
  • Wait 5 minutes or so until complete
  • Close
  • Re-insert SQM-LU device
  • Wait 5 minutes or so for Windows to install driver and port. If Windows fails to install the driver, it will have to be manually installed with the "setup executable" available from (see the comments column on that page for the latest link).
Connected meters (SQM-LE/LU/LR/DL) / FITS header integration
« Last post by admin on September 03, 2014, 12:38:37 am »
Here is a page showing some programs that integrate the SQM data (from the connected meters) into FITS headers:
General Discussion / Stop light pollution and glare from luminous signs
« Last post by admin on August 06, 2014, 05:18:39 pm »
You may be interested in this Indiegogo campaign to help "Stop light
pollution and glare from luminous signs":
Connected meters (SQM-LE/LU/LR/DL) / Firmware updates
« Last post by admin on August 05, 2014, 12:35:27 pm »
Shipments of DL units between June 27 2014 and August 1, 2014  (Firmware feature version 27) had a firmware problem where battery-powered power-save-mode readings may have been missed.

A new version (feature 29) correcting that issue is available here:

Units with the older version 25 firmware do not need to be updated, the bug does not exist in that version.

Sorry for the inconvenience.
General Discussion / Report: Article on Light pollution in Hong Kong ...
« Last post by admin on May 27, 2014, 10:46:39 pm »
Title: Contributions of artificial lighting sources on light pollution in Hong Kong measured through a night sky brightness monitoring network
 By: Chun Shing Jason Pun, Chu Wing So, Wai Yan Leung, Chung Fai Wong
  Science Direct:
  arXiv (Free):

  Light pollution is a form of environmental degradation in which excessive artificial outdoor lighting, such as street lamps, neon signs, and illuminated signboards, affects the natural environment and the ecosystem. Poorly designed outdoor lighting not only wastes energy, money, and valuable Earth resources, but also robs us of our beautiful night sky. Effects of light pollution on the night sky can be evaluated by the skyglow caused by these artificial lighting sources, through measurements of the night sky brightness (NSB). The Hong Kong Night Sky Brightness Monitoring Network (NSN) was established to monitor in detail the conditions of light pollution in Hong Kong. Monitoring stations were set up throughout the city covering a wide range of urban and rural settings to continuously measure the variations of the NSB. Over 4.6 million night sky measurements were collected from 18 distinct locations between May 2010 and March 2013. This huge dataset, over two thousand times larger than our previous survey, forms the backbone for studies of the temporal and geographical variations of this environmental parameter and its correlation with various natural and artificial factors. The concepts and methodology of the NSN were presented here, together with an analysis of the overall night sky conditions in Hong Kong. The average NSB in Hong Kong, excluding data affected by the Moon, was 16.8 mag arcsec−2, or 82 times brighter than the dark site standard established by the International Astronomical Union (IAU). The urban night sky was on average 15 times brighter than that in a rural location, firmly establishing the effects of artificial lighting sources on the night sky.
General Discussion / Report: Human Contrast Threshold and Astronomical Visibility
« Last post by admin on May 20, 2014, 05:48:27 pm »
Andrew Crumey has written a paper that you might be interested in:
  "Human Contrast Threshold and Astronomical Visibility" (accepted in
  MNRAS). It presents a model which gives visibility predictions somewhat
  different from the standard Hecht-Schaefer model, but in better
  agreement with the laboratory data (Blackwell, Knoll et al). In the
  conclusions, Andrew makes some proposals regarding sky quality
  indicators for public use.
General Discussion / Overlay of different SQM measurements
« Last post by infographic_ch on March 02, 2014, 09:28:02 pm »
Dear all,
I am a GIS student. Currently, I am preparing a paper on the modelling of light pollution.
The approach is to measure night sky brightness with a SQM at various spots in an urban area.
e.g. close to a highway,  close to a primary street, etc.
For my model I have consider that each of those measurements can overlap.
I need to understand how individual SQM measurements add up if they overlap.
I am looking for a formula that applies for the combination of light sources measured in 'mags/arcsec2'.
Anyone is experienced in this field?
General Discussion / Re: SQM-LU and INDI
« Last post by BPO on February 27, 2014, 08:47:37 pm »
Brilliant! INDI gets better every day.
Weatherproofing / Re: Drainage
« Last post by BPO on February 27, 2014, 08:39:11 pm »
Hi Anthony.

Thanks for the info. I was concerned I'd crack the plastic and have to buy new ones: Great for you, but not so good for me!


Now that I know the plastic likely won't cause any problems, I have hole cutter bits that will do the job easily.

Also, the new holes will be covered by the foam already in the base of the enclosure.


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