Hi,

A while ago I asked here if anyone would be interested in getting equipment and joining an international light meter network. I finally got my meter installed over the past couple of days to get some calibration data:



There is a tree blocking a part of the eastern horizon which I hoped would not be a problem but it might be afterall. You can see the jump in the readings at 10am UTC where the sun pops out from behind the tree and rays directly hit the sensor! I'm not concerned about astronomical effects like this since but I'll need to investigate any possible effect of reflected street lighting hitting the sensor from the tree...

Anyway thats 3 stations up and running in Ireland now, Astroshot Observatory and TCD have the other two.

logscale for the night time data



not sure if thats clouds over the moon or the tree causing the dips

Good to see your results Al.
Which reminds me, I must get off my butt and upload my results!

Michael.

Al,

Below are the results from a few consecutive days in April.



These are from the main sensor.
Unfortunately, the light meter is not in the best location - on the ground between my dome and the shed.
Ideally, it should be raised a bit to increase the exposure to the sky.

I hope to calculate Lux values shortly.

Michael.

Interesting projects lads. What is the background here (equipment, set up, etc.)

Seanie.

Lux Values



Are the variations in values due to the effects of the intermittent cloud?

Michael.

At the 9th European Symposium for the Protection of the Night Sky, the issue of recording the level of illumination of the night sky by scientific means was discussed. As I understand it, and Al may explain it better than I can, the purpose behind this is to provide a scientific measurement of the night sky illumination using an appropriate electronic device. Once illumination from the Sun and Moon are removed, one can begin to quantify the level of light pollution at a particular location. With many of these sensors across a wide area, once can see variations in light pollution between difference locations. Also, by running the sensor regularly, one can monitor the reduction or increase of light pollution at a particular location.

The sensor consists of a small glass panel, approx 3-4 inches square x 0.5 inches thick in an aluminium frame. This contains a number of sensors and produces a log in a .csv file to the following format:
1.Date;
2.Time;
3.Temperature;
4.°C;
5.Main sensor counts;
6.Daysensor visual counts;
7.Daysensor near infrared counts;
8.Status message, i.e. "ok" or "err".

The piece of kit cost approx 100euro.
The sensor is connected to a PC with a USB cable and let run for as long as one wishes.
From here, one can calculate Lux values etc.

Hope this explains it a little.

Michael.

Assuming my calculations are correct and 683.002 Lux = 1 W/m2:



Now Al, how does one convert this to an equivalent limiting magnitude?

Michael.

Thanks for that Mike, it sounds like an interesting project. I just might give it a go for fun than anything else!

If there were enough of these across member's locations in Ireland, we could probably com up with a rudimentary map of light pollution intensity.

Seanie.

Seanie_Morris wrote:
If there were enough of these across member's locations in Ireland, we could probably com up with a rudimentary map of light pollution intensity.
[/quote]
I wrote a little bit of code to get the gps position from my garmin and log that with the light pollution reading. So in theory I can now map by driving around The only problem is that I need to get back on the roof of the house to take the meter off and put it on the car!

albertw wrote:

I wrote a little bit of code to get the gps position from my garmin and log that with the light pollution reading. So in theory I can now map by driving around The only problem is that I need to get back on the roof of the house to take the meter off and put it on the car!

Off you go so!