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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,
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.
SQM-LU-DL (Datalogging light meter) / 3 new DLs installed...
« Last post by darkwightskies on December 10, 2014, 03:46:39 pm »
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?
At a recent meeting of the Loss of the Night Network (, 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:


2) GLOBE at Night via smartphone or regular computer:

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/

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.


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:
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.

Dan Klinglesmith
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.


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:

(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:

Christopher Kyba

Helmholtz-Zentrum Potsdam
Deutsches GeoForschungsZentrum GFZ
General Discussion / Re: Naked Eye Limiting Magnitude
« Last post by kyba on November 28, 2014, 01:02:55 pm »
Hello Dan,

I just wanted to let you know that if you'd like to share your data with researchers, it is best to store it in the community standard format that we developed two years ago:

If you are interested, Kai Pong Tong from Bremen has a Python script to read out an SQM and print the header and information in the standard format that he would be willing to share with you. If you are interested, please send me an email. My contact information is here:

Christopher Kyba
General Discussion / Re: Naked Eye Limiting Magnitude
« Last post by admin on November 27, 2014, 12:38:59 pm »
I have a simple python script running for the SQM-LR.  Still need to generate a nightly graph.

How is the Naked Eye Limiting Magnitude calculated?  I did not see it coming back from the instrument.

cheers, Dan Klinglesmith

Hi Dan,

NELM calculation can be found here:


Or using this chart which also depicts the not so precise conversion to NELM because of differences in human vision:

General Discussion / Naked Eye Limiting Magnitude
« Last post by dklinglesmith on November 27, 2014, 04:08:16 am »
I have a simple python script running for the SQM-LR.  Still need to generate a nightly graph.

How is the Naked Eye Limiting Magnitude calculated?  I did not see it coming back from the instrument.

cheers, Dan Klinglesmith

Connected meters (SQM-LE/LU/LR/DL) / Recover firmware
« Last post by admin on November 10, 2014, 02:44:21 pm »
If your connected SQM experiences a problem after a firmware upload, the unit might be easily recovered back to an operational state.

The firmware upload only writes to the "program" area of the unit. The bootload area, calibration data and serial number are untouched.

For the first 3 seconds after power-up, the unit is waiting for a firmware upload.

You should be able to reload the original firmware as follows:
  • Start up the latest UDM software which you can get from here:
  • Press "Find", your SQM should be displayed in the Found-devices window. If no device shows up in the found list, then there is another problem which cannot be fixed by this procedure.
  • UDM may try to read from the device and fail, don't worry about that for now.
  • Go to the firmware Tab, and "Select Firmware" then choose the appropriate firmware for your device. You may have to also select "All Firmware" at the bottom right of the "Open Existing File" dialog since it might automatically be showing other types. Select the desired firmware for your unit (note that SQM-LE files are also used for the SQM-LU).

        Do not press the Load button yet.
  • Unplug the SQM then plug it back in then press the "Load Firmware" button within 1-2 seconds. If the progress bar starts incrementing, then the meter will work fine, otherwise there is likely a hardware issue that needs repair.
  • The firmware should completely load. After the progress bar as completed then press "Find" in UDM to re-find the meter.
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