[SQM] Little changing in SQM-network data collection

Christopher Kyba christopher.kyba at wew.fu-berlin.de
Thu Jul 12 13:48:31 UTC 2012

Hi Massimo,

The variability that you get from -ux rather than -rx is just "noise".
 Specifically, it looks like the SQM sometimes picks up an external EM
field and this causes the readings to jump around.  The point at which
the jumps start and the size of the jumps are not consistent from SQM
to SQM, and I think it is non-existent for the SQM-LU.

I very strongly recommend that you do not take measurements with -ux!
It will simply make your light pollution data worse by adding
non-Gaussian "jitter".  It must surely be much better to modify your
cloudy/clear detection algorithm to work with noise-removed data than
to add a bunch of noise into the data collection.

I have been hoping to hear back from you regarding the skyglow data
format that Dorien Lolkema and I proposed, which has now been modified
and altered based on feedback from the community.  You can find the
most recent version of the format here:

I hope you will get back to me about the format, because we would
really appreciate your input based on your experience running the
network.  I also hope that you'll adopt the format for GECO when it is
finalized this fall.  You can always write out two files in order to
not break your current scripts.

Best wishes,


On Thu, Jul 12, 2012 at 12:37 PM, Massimo Alessandria
<massimo at bresciaraduno.it> wrote:
> Hello to everybody,
> with the release of firmware version 21  of the SQM-LE, has been introduced
> a substantial change in data collection.
> Now, with the command -rx, we obtain already averaged data over a longer
> period. As you know, our management algorithm of charts and calculations
> automatically processes the variability of the readings; so it's be able to
> predict if the sky is clear or cloudy and then calculate the average SQM
> value only in clear sky periods.
> With the firmware version 21 of the SQM-LE, our algorithm no longer worked
> properly, because it gets measurements with less high variability, and thus
> it happens that "some" cloudy skies are identified as clear.
> So we have made changes to the servers (operant since 10th July 2012), so
> they collect - for the firmware version 21 and higher - readings with the
> -ux parameter, which takes not averaged data, so we can identify with more
> accuracy if the sky is clear or cloudy.
> We remember you that www.sqm-network.com is a big network to collect data on
> light pollution, collected by SQM-LE. This monitoring program - as you know
> - is completely free and non-profit. Sqm-network provides a set of tools to
> those who are members, which greatly simplifies the processing of data
> collection. In short time, thanks to our software GECO (you can freely
> download it from our site ),  you'll be able to integrate into the network
> also the USB version SQM-LU (not currently supported).
> For further information, please contact me at info at sqm-network.com
> Clear skies to all
> --
> Massimo Alessandria
> Gruppo Astrofili Deep-Sky (GADS)
> www.bresciaraduno.it
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