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SQM-LU / Re: Extending the USB cable
« Last post by admin on November 01, 2012, 10:18:21 pm »
We have only tested that one (IOGEAR) brand. It has the advantage of you using your own cable at your desired length (up to 198164'). And, since it uses Ethernet cable, it can be terminated after the wire is strung through walls etc..

I think the USB extension cables should be just as reliable as the IOGEAR module. The extension cables I saw a while ago did not go up to 198164', that may be different now.

Please let us know if you find one that works for you, or which one you are considering to try.
SQM-LU / Re: Extending the USB cable
« Last post by Rainer on November 01, 2012, 09:32:05 pm »
Hi Anthony,

Thanks for that tip. I am just doing a search for different brands of this type of adapters.

How reliable are they compared to USB extensions ?
General Discussion / IR Filter spec sheet
« Last post by admin on October 27, 2012, 07:08:12 pm »
The SQM products use a HOYA CM-500 filter. The full specification sheet which includes response data points can be found here now.

The SQM response plot can be found in the PDF Report on SQM by Pierantonio Cinzano.
SQM-LU-DL (Datalogging light meter) / Updated manual
« Last post by admin on October 27, 2012, 03:57:45 pm »
Documentation update: An uncalibrated SQM-LU-DL unit may respond to the "Return one logged record" with a leading mpsas negative sign:

Uncalibrated (negative sign):
Sent: L40000000001x   To: /dev/ttyUSB1   Received: L4,00-01-01 1 01:00:01,-11.52, 019.3C,225

Calibrated (no negative sign):
Sent: L40000000011x   To: /dev/ttyUSB1   Received: L4,00-01-01 1 00:00:21,08.51, 018.6C,222

This means that there may be one extra character (negative sign) in the response field. Comma separation is the better choice when parsing this response.

Updated manual here, see section
General Discussion / Turtle studies
« Last post by admin on October 24, 2012, 07:42:21 pm »
Some researchers have used the SQM light meters for studying the effects of artificial lighting on sea turtle habits.

A few points about such studies would be:
  • The Field of View (FOV) may be critical in your tests, see this chart. If you are using the meter as a directional light meter then the SQM-L model would be the best suited to pointing at specific bright spots.
  • If you are taking sample readings over a period of time for comparison, make sure that the meter is located at the same spot and facing the same direction each time. It may be a good idea to have a registration stand (peg in the ground with a holder for the meter) to ensure that the meter is always facing the same direction for each successive sample.
  • Also be aware that the FOV will capture obstructions like your body, so be sure to always hold the meter in the exact same direction above your head (to avoid and shading or reflection from your body into the meter sensor).
  • You may want to gather readings from both Zenith (straight up) and various angles towards and away from the shore vertically and horizontally to get an idea of what the Turtles would see in their travels.
  • Make sure you record the time and date as the Moon will heavily influence sky brightness. Even if the night is very overcast, a moonlit night will provide a wide range if readings. You will get the most consistent readings on moonless nights.
  • If you have the funds, and access to a secure site on the beach, you may want to consider the SQM-LU-DL which can sit unattended for months collecting readings for later retrieval.
  • The meter will likely not saturate at all in the night, even if you point it directly at distant condominium or hotel lighting.
  • Please see this report (by Pierantonio Cinzano) for spectral response of the meter and other scientific details.
  • A longterm exposure photo of the beach-line may be a good base image to obtain relative brightnesses so that light readings can be noted on there.

Here are some resources:
Please reply with your comments regarding details about your own studies or questions.
General Discussion / Notifications
« Last post by admin on October 23, 2012, 05:30:02 pm »
Since many members have come from the mailing list where all messages went to all members, you may like getting emails on every single posting to this forum. This can now be done by going to Profile->Modify_Profile->Notifications

Ensure the following is set:

  "For topics and boards I've requested notification on, notify me: Instantly"

As shown here:

You must also select "Notify" on each board. For example in the "General Disscussion category" board, there is a "Notify" button near the top right side:

This is a new setting being tested (Board Notification Mod), hopefully it works well.
SQM-LU / Extending the USB cable
« Last post by admin on October 23, 2012, 03:47:59 am »
The SQM-LU and SQM-LU-DL come with a standard 15ft (5m) cable which is the design limit for a standard USB connection.

A USB cable extender may be used if you require a longer connection.

We have successfully used the IOGEAR GUCE62 which uses an Ethernet cable (Cat5e, or Cat6) to achieve up to a 164' extension:

* One customer reported problems with a different model (GUCE51), so we now recommend the above GUCE62 which comes with a power  supply (not shown).
SQM & SQM-L Handheld light meters / Battery connection
« Last post by admin on October 23, 2012, 01:36:43 am »
If the meter does not start despite having a fresh battery, the cause may be a loose battery clip.

Using pliers, lightly squeeze the 6 petals around the flower-shaped connector as shown in the image below:

Dear all,

1) I am very glad to learn about this new forum on the same day that I started to write a series of posts on my blog, under the title of " brief history of participatory night sky monitoring from Italy".

2) the posts will be available in Italian and English, and here is a preface: (ENGLISH) (ITALIAN)

3) I hope this will be of interest to forum readers, as a minimum as a quite composit case history of Unihedron products, even though -based on feedback we had in the past, I am quit sure some of you will appreciate more than just the sensor technology side of the story proposed in the blog.

thank you for your attention, and regards

Andrea Giacomelli (aka pibinko)

DISCLAIMER: the blogs posts on the "brief history of participatory night sky monitoring from Italy" are freely inspired from the BuioMetria Partecipativa project (, of which I am one of the creators.
However the BSDBPM blog posts will not represent an official position of the project...while this is evolving steadily, I saw the value of also providing a more personal view on some of the episodes we have been living and working through. Please refer to or to for the BuioMetria Partecipativa project itself.
General Discussion / Choosing a Unihedron dark sky light meter
« Last post by admin on October 22, 2012, 01:31:13 pm »
Unihedron offers the following variations on the dark sky light meter categorized into hand-held or connected models.

Hand-held meters:
The best choice for casual astronomy or environmental dark sky measurements is the SQM-L. It is a hand-held model that provides a quick reading. The narrow field of view (~20°) is suitable for urban and rural settings.

The SQM has a wide field of response (~42°) which is more suited for rural use where trees or streetlights are not directly in the field of view.

Connected meters:
If you want the readings sent directly to a computer, but not instantly readable in your hand, then one of the connected models is a better choice. Software running on a computer must be used to read and/or record the light value from the meter. All connected meters use the narrow field of view like the SQM-L, and custom orders can be made to remove the lens if necessary.

The SQM-LU (USB) connects with a 15ft (3m) USB cable to a computer.  A cable extender could be used to obtain a 198ft extension.

The SQM-LE (Ethernet) connects to either a computer or network router with an Ethernet cable and must also be powered separately (AC adapter included). The readings can also be directly read over the Internet.

The SQM-LU-DL can be powered by an external battery pack (included) and take readings autonomously over extended periods. This model is suitable for gathering unattended readings from a remote site. The readings can be downloaded to a computer later with the supplied USB cable.

The SQM-LR (RS232) connects to a computer with an RS232 cable (6ft is supplied, 300 ft max) and must also be powered separately (AC adapter included). This is useful for computers or modems that have an RS232 connection.

FOV (Field of view): The field of view is not a sharp edged cone, there is some drop off as shown here: FOV curves. The value reported is the Full Width Half Maximum (FWHM)
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