Recent Posts

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71
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:
  http://unihedron.com/projects/darksky/cd/SQM-LU-DL/firmware/SQM-LU-DL-4-6-29.hex

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.
72
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: http://www.sciencedirect.com/science/article/pii/S0022407313004950
  arXiv (Free): http://arxiv.org/abs/1401.1200

Abstract:
  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.
73
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.

  http://arxiv.org/abs/1405.4209
74
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?
Thanks,
Stefan
75
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.
76
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!

 ;D

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.


Cheers,

Gary
77
Weatherproofing / Re: Drainage
« Last post by admin on February 27, 2014, 02:00:07 pm »
The base caps of both my SQM-LE enclosures have flexi-conduit connectors fitted, and I suspect they have raised rims internally which prevent any accumulated moisture in the enclosure from draining via the hole. How difficult is it to drill the plastic? Does it crack easily, or is it an easy job?

Thank you for your question Gary.

The white housing caps (and tube) are made of PVC. Here are some points below about how I deal with PVC:
  • It is a relatively soft plastic that does not crack easily. It might crack if stressed/cut at very low temperatures, but room temperature is warm enough to work with it without worrying too much about cracking.
  • The biggest problem I found with cutting PVC is that the cutting tool may grab too easily. I use a dulled drill-bit or hole-saw to prevent grabbing. You can either slightly round the sharp tip edges of the bit with a file, or purchase a special bit for plastic cutting to prevent grabbing (both of which would likely be overkill for your application). Cut at a slow speed, I use 570RPM. Occasionally clean out the excess shavings from the drill bit during use to prevent buildup which will cause the plastic to melt and bind easily.
  • I have also had great success with a carving knife. Carve small strips of the plastic to eventually get the shape you want. Box-cutter blades are too thin and sharp to work with nicely, but a pocket knife seems to work well.

If you are adding drain holes, make sure to cover the inside with a screen to prevent bugs crawling back up there.

Best wishes,
Anthony Tekatch
78
Weatherproofing / Re: Drainage
« Last post by BPO on February 27, 2014, 09:53:58 am »
Hi Anthony.

The base caps of both my SQM-LE enclosures have flexi-conduit connectors fitted, and I suspect they have raised rims internally which prevent any accumulated moisture in the enclosure from draining via the hole. How difficult is it to drill the plastic? Does it crack easily, or is it an easy job?


Cheers,

Gary Roberts
Benmore Peak Observatory
New Zealand
79
General Discussion / Reports
« Last post by admin on February 16, 2014, 07:55:23 pm »
Two new papers on light pollution have been published in a highly respected journal, the "Journal of Quantitative Spectroscopy and Radiative Transfer":
  • "Night sky photometry and spectroscopy performed at the Vienna University Observatory": Science Direct, arXiv.
  • "The night sky brightness at Potsdam-Babelsberg including overcast and moonlit conditions": Science Direct, arXiv.
80
General Discussion / SQM-LU and INDI
« Last post by ffernandez on January 14, 2014, 05:06:58 pm »
Hello,

  SQML-LU is now supported by INDI project (http://www.indilib.org/develop/indiforjava/i4jdrivers/sqm-lu-driver.html). Sergio Alonso main developer of "INDI for Java" project  has created this driver.
 
  Soon, we'll be able to announce a new version  of Maroc (http://www.luz-cero.es/maroc) with INDI support. Any INDI compatible mount will be controlled by Maroc and also SQM-LU readings will be request using INDI protocol.
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