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51
Connected meters (SQM-LE/LU/LR/DL) / APT - Astro Photography Tool
« Last post by admin on March 19, 2015, 10:53:28 pm »
"Astro Photography Tool", a Swiss army knife for your astro imaging sessions now incorporates SQM readings. You can check out all the features at www.ideiki.com/astro/.

Here is the latest screenshot demo:

52
General Discussion / Paper: Worldwide variations in artificial skyglow
« Last post by admin on February 13, 2015, 12:34:07 am »
Congratulations to Christopher C. M. Kyba, Kai Pong Tong, and many other contributors on the publication of their paper:

  Worldwide variations in artificial skyglow

From the Abstract:
Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope, and typically of short duration. In this first major international compilation of monitoring data we answer several key questions about skyglow properties. Skyglow is observed to vary over four orders of magnitude, a range hundreds of times larger than was the case before artificial light. Nearly all of the study sites were polluted by artificial light. A non-linear relationship is observed between the sky brightness on clear and overcast nights, with a change in behavior near the rural to urban landuse transition. Overcast skies ranged from a third darker to almost 18 times brighter than clear. Clear sky radiances estimated by the World Atlas of Artificial Night Sky Brightness were found to be overestimated by ~25%; our dataset will play an important role in the calibration and ground truthing of future skyglow models. Most of the brightly lit sites darkened as the night progressed, typically by ~5% per hour. The great variation in skyglow radiance observed from site-to-site and with changing meteorological conditions underlines the need for a long-term international monitoring program.

Read the full paper here:
  http://www.nature.com/srep/2015/150212/srep08409/full/srep08409.html

Much hard work was involved in gathering and standardizing readings from all over the world.
53
Weatherproofing / Unihedron enclosures
« Last post by BPO on January 08, 2015, 08:05:05 am »
Hi. One of my two enclosures recently lost its glass window for unknown reasons, possibly a combination of high UV exposure (it's on a mountaintop) and high winds.

So, don't forget to inspect your enclosures every now and again, just in case!

 8)
54
SQM-LU-DL (Datalogging light meter) / Re: 3 new DLs installed...
« Last post by admin on December 10, 2014, 10:33:13 pm »
Can you run a test locally to ensure that the units can record from battery and that you can retrieve the data? Such a test should only take an hour or two if your setting is on "once per hour".

Also, make sure that you are using the UDM software that came with the units or get the latest version from here:

http://unihedron.com/projects/darksky/cd/SQM-LU-DL.html

I look forward to solving this issue.
55
SQM-LU-DL (Datalogging light meter) / Re: 3 new DLs installed...
« Last post by darkwightskies on December 10, 2014, 10:16:32 pm »
Thanks for the very quick response
  • All testing was done in the Data-logging mode
  • Threshold was initially set to 14 to avoid collecting daytime readings but as we are in a basically dark skies area it should have been overridden at night, it is now set to 0.
  • The LED was showing every minute
  • The  2 units have been reset to ensure compliance with the settings you suggest and will be checked again in a few days.
Once again, thanks for your reply, let's hope for some results when we next visit the sites… i'll let you know either way,
56
SQM-LU-DL (Datalogging light meter) / Re: 3 new DLs installed...
« Last post by admin on December 10, 2014, 04:02:12 pm »
There are two ways to gather readings with the DL meter:
  • Log continuous mode: Available from the information tab. This method does not set the internal battery operated datalogging features. If you initially tested the unit with this mode, then the battery operation settings will not be set to the same setting as in Log continuous.
  • Datalogging tab: Settings on the datalogging tab are stored in FLASH memory inside the meter. These settings control how the meter records while connected to the battery.

If you noticed that no readings are being recorded at all, then check the threshold setting on the datalogging tab. It should be 0. Anything greater will prevent datalogging on readings below that value.

Also, when plugging in the battery pack to the meter, the LED should be visible for three seconds every minute.

Please let me know if you have further questions or still have problems.
57
SQM-LU-DL (Datalogging light meter) / 3 new DLs installed...
« Last post by darkwightskies on December 10, 2014, 03:46:39 pm »
Hi,
We've just installed 3 new DLs here on the Isle of Wight UK and unfortunately have  had problems with 2 of them.

We followed the manual's instructions to the letter, charging the supercap overnight and then selecting 1 reading on the hour every hour, attaching battery pack etc. The Header basic details were also set with Timezone and location etc.

Returning to the meters a week later we found neither had made any readings although the devices appeared to be operating normally.

Testing back at base showed them both working fine when shorter time periods were set eg every 5 minutes 1/12.

I'm not sure what to do next as it is an inconvenience to keep visiting site just to check operation. Are we missing something?
58
At a recent meeting of the Loss of the Night Network (http://www.cost-lonne.eu/), the participants produced a recommendation for the best practice in taking SQM observations. I've slightly revised the instructions for clarity, and added some additional information below:



We suggest that you only take observations on totally clear or totally overcast, moon-free nights. There is too much variation on partly cloudy or moonlit nights for the data to be analyzed. If you are going out into the cold from a warm room, give the SQM a few minutes to cool off before you begin your observations.

First, push the measurement button 3-4 times before you begin the actual measurement. This is recommended by Unihedron, because the first measurements are sometimes biased as the electronics turn on after a long period of being off.

Next, arrange your body so that you are looking in one of the four compass directions, and take a measurement with the SQM pointing towards zenith. Record the measurement, then turn 90 degrees and repeat the observation. Take four measurements in total, one for each compass direction. If the SQM-L is being affected by stray light or EMF, this may minimize or reveal the effect.

If the four observations are not self-consistent (maximum range about 0.2 magSQM/arcsec2), then it is probably not a good measurement location, and the data should not be recorded.

If the measurements are consistent, record the sky brightness as the mean (average) of the four measurements.

Please share your observations with the scientific community! There are several easy ways to do this:

1) Smartphone apps: You can submit your observations using the free "Loss of the Night" app:

Android: https://play.google.com/store/apps/details?id=com.cosalux.welovestars
iOS: https://itunes.apple.com/en/app/loss-of-the-night/id928440562

2) GLOBE at Night via smartphone or regular computer: http://www.globeatnight.org/webapp/

3) GLOBE at Night via spreadsheet: If you are planning on taking a lot of handheld observations, you may prefer to record them all and then pass the data on to GLOBE at Night at once. If you do this, please ensure that your sheet includes the following data, preferably in this order:

latitude, longitude, day, month, year, hour, minute, SQM value, SQM serial number, cloud cover, (optional sky comment), (optional location comment), country

Please record cloud cover as "clear" or "overcast".

Send your spread sheet to Dave Bell at GLOBE at Night. His email address is dbell /at/ noao.edu


Why is it important to record observations? You probably already know this, but the way the world is being lit is changing, and many communities are adopting LED lights. No one knows whether this is going to make the sky brighter or darker, and if we have information about how skyglow is changing in different communities, we may be able to influence future lighting changes for the better.

Notes:

1) The technique of making 4 measurements with different orientations was suggested to us by Andreas Hänel.
2) If you're curious about whether or not handheld measurements from different people and meters are useful for science, you can read our report analyzing 4 years of GLOBE at Night handheld SQM data: http://www.nature.com/srep/2013/130516/srep01835/full/srep01835.html?WT.ec_id=SREP-704-20130603
59
General Discussion / Re: Naked Eye Limiting Magnitude
« Last post by dklinglesmith on December 01, 2014, 06:05:45 am »
thanks for the information and links.

cheers,
Dan Klinglesmith
60
General Discussion / Easy way to store SQM-L observations with GLOBE at Night
« Last post by kyba on November 28, 2014, 01:13:02 pm »
I just wanted to let everyone know that there's now an even easier way to add your SQM-L observations to the GLOBE at Night database.

If you have an Android or iOS device, you can download the free Loss of the Night app, and use it to submit your data.

Android: https://play.google.com/store/apps/details?id=com.cosalux.welovestars
iOS: https://itunes.apple.com/en/app/loss-of-the-night/id928440562

If you are doing a moving survey with locations less than five minutes apart, it would be safest to quit the application and restart it in order to make sure that the GPS position is updated for each location.

After your survey is completed, you can download your data from GLOBE at Night here: http://www.globeatnight.org/mapapp/

(choose the region you're interested in, make the map, and click "download CSV" in the bottom left)

If you are in a light polluted area, we'd also really appreciate if you'd try out using the app to do a visual observation of the naked eye limiting magnitude. Paired data with both a NELM and SQM observation are incredibly valuable to us!

We want to use handheld SQM-L and naked eye observations to understand how skyglow is changing worldwide. Here's an open access data in which we show how useful this data is: http://www.nature.com/srep/2013/130516/srep01835/full/srep01835.html

Christopher Kyba
http://userpage.fu-berlin.de/~kyba/

Helmholtz-Zentrum Potsdam
Deutsches GeoForschungsZentrum GFZ
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