53 replies to this topic

[mr.otswons]

Most commonly used LED lights have huge spectral peak emissions in near UV and blue. Like the Unihendron Sky Quality Meters, many 'normal' imaging satellite sensors are not sensitive (basically blind) to the bluer, highly scattering, wavelengths of LED light pollution, so the increases go 'un-detected.'

Thanks for the deeper dive on the topic. Are you aware of any plans, projects, new satellites to capture the new blue light?

[RLK1]

Thanks for the deeper dive on the topic. Are you aware of any plans, projects, new satellites to capture the new blue light?

Newer satellites are being equipped to monitor the spectral changes in light pollution.

 

I have queried Unihedron earlier in the year regarding the SQM usage : 

 

"From a current discussion on an amateur website, "cloudy nights", there seems to be an equivocation of how effective an SQM remains due to blue light emanations from LED lighting and a so-called lack of blue sensitivity of the SQM.

I'm doubting the latter as I consider the SQM to be reliable despite newly installed LED lighting in various cities and I note the latter can vary between about 2700k to 4000k or so and that's quite a spread in and of itself.

At any rate, I'd like your "take" on the above."

 

Unihedron's response:

 

"Thank you for your question."

"Yes, the spectral response of the SQM products is not exactly the same as
the response of the human eye. The SQM uses a standard IR filter
(HOYA-CM500) found in astronomy and cameras to compensate the response of
silicon light sensor.

More details of the exact spectrum compared with other responses can be
found in this paper:
  http://unihedron.com...report_v1p4.pdf
  See Fig. 12.

We do not have a model with other filters, but we do offer the removal
of the IR filter and an external filter adapter for those who want to
experiment with their own filters."

[Ron359]

Newer satellites are being equipped to monitor the spectral changes in light pollution.

 

I have queried Unihedron earlier in the year regarding the SQM usage : 

 

"From a current discussion on an amateur website, "cloudy nights", there seems to be an equivocation of how effective an SQM remains due to blue light emanations from LED lighting and a so-called lack of blue sensitivity of the SQM.

I'm doubting the latter as I consider the SQM to be reliable despite newly installed LED lighting in various cities and I note the latter can vary between about 2700k to 4000k or so and that's quite a spread in and of itself.

At any rate, I'd like your "take" on the above."

 

Unihedron's response:

 

"Thank you for your question."

"Yes, the spectral response of the SQM products is not exactly the same as
the response of the human eye. The SQM uses a standard IR filter
(HOYA-CM500) found in astronomy and cameras to compensate the response of
silicon light sensor.

More details of the exact spectrum compared with other responses can be
found in this paper:
  http://unihedron.com...report_v1p4.pdf
  See Fig. 12.

We do not have a model with other filters, but we do offer the removal
of the IR filter and an external filter adapter for those who want to
experiment with their own filters."

There has been no equivocation about the lack of blue sensitivity of SQM's.   Its been well known,  because they have had the information on their website for at least 20 years.   A pro-astronomer and the CO State IDA coordinator I worked with was constantly  pointing out this 'feature' to us maybe even before Y2K.    Rather then assume a little red LED readout with a decimal point,  is just as accurate as an atomic clock,  the stated limits on precision and accuracy of the SQMs readings, all 'amateurs' need to do is read whats in the instruction manual or on the Unihedron website.   

Edited by Ron359, 29 October 2024 - 10:18 PM.

[RLK1]

There has been no equivocation about the lack of blue sensitivity of SQM's.   Its been well known,  because they have had the information on their website for at least 20 years.   A pro-astronomer and the CO State IDA coordinator I worked with was constantly  pointing out this 'feature' to us maybe even before Y2K.    Rather then assume a little red LED readout with a decimal point,  is just as accurate as an atomic clock,  the stated limits on precision and accuracy of the SQMs readings, all 'amateurs' need to do is read whats in the instruction manual or on the Unihedron website.   

I doubt anyone thinks an SQM is as accurate as an atomic clock and the changeover to LED street lighting for many cities and towns is certainly a more recent makeover than just a decade ago, let alone 20 years.

 

That said, I'm not going down the same path again with you on the usage of an SQM since we've been back and forth over it on prior threads.

 

For anyone else who truly wants an in depth review of the the methods used to assess the brightness of the night sky, including the SQM, see the link for the pdf by Dr Barentine:

 

https://www.research..._and_Monitoring

[mr.otswons]

Newer satellites are being equipped to monitor the spectral changes in light pollution.

 

I have queried Unihedron earlier in the year regarding the SQM usage : 

 

"From a current discussion on an amateur website, "cloudy nights", there seems to be an equivocation of how effective an SQM remains due to blue light emanations from LED lighting and a so-called lack of blue sensitivity of the SQM.

I'm doubting the latter as I consider the SQM to be reliable despite newly installed LED lighting in various cities and I note the latter can vary between about 2700k to 4000k or so and that's quite a spread in and of itself.

At any rate, I'd like your "take" on the above."

 

Unihedron's response:

 

"Thank you for your question."

"Yes, the spectral response of the SQM products is not exactly the same as
the response of the human eye. The SQM uses a standard IR filter
(HOYA-CM500) found in astronomy and cameras to compensate the response of
silicon light sensor.

More details of the exact spectrum compared with other responses can be
found in this paper:
  http://unihedron.com...report_v1p4.pdf
  See Fig. 12.

We do not have a model with other filters, but we do offer the removal
of the IR filter and an external filter adapter for those who want to
experiment with their own filters."

Thanks! It will be great to see the data from the newer satellites, when it becomes available.

 

The answer from Unihedron however went a little bit above my head. Do they mean that they have no plans to adjust to the led/blue light, or that you think it is already adequate?

 

In any case, I get that practically all readings from an instrument will be different from the light/dark experienced by the eye. What I would like though, is to give our municipality concrete data on light pollution over the years. 

[mountain monk]

While I have enjoyed the discussion about this subject for about fifteen years now, at a certain point one has to decide how to communicate about sky darkness. I have decided to use DaveL’s map data and mpsas. No doubt the discussion will continue for another fifteen years, at least.

 

Dark skies.

 

Jack

[RLK1]

Thanks! It will be great to see the data from the newer satellites, when it becomes available.

 

The answer from Unihedron however went a little bit above my head. Do they mean that they have no plans to adjust to the led/blue light, or that you think it is already adequate?

 

In any case, I get that practically all readings from an instrument will be different from the light/dark experienced by the eye. What I would like though, is to give our municipality concrete data on light pollution over the years. 

"The answer from Unihedron however went a little bit above my head. Do they mean that they have no plans to adjust to the led/blue light, or that you think it is already adequate?"

 

It's more than adequate in a dark sky meaning in a so-called bortle 1 or 2 or so region where you don't have LED or other forms of ground based illumination present so the issue of blue sensitivity isn't a significant factor.

 

DaveL’s map data and mpsas, as noted in post #31, is adequate.

 

In light polluted areas, even LED illumination may not be uniform meaning there are warm color temperature dark sky approved LED street light fixtures (typically @2700k) installed by some municipalities that do not have a significant blue component so the SQM may be adequate as well. 

[RLK1]

Thanks! It will be great to see the data from the newer satellites, when it becomes available.

 

The answer from Unihedron however went a little bit above my head. Do they mean that they have no plans to adjust to the led/blue light, or that you think it is already adequate?

 

In any case, I get that practically all readings from an instrument will be different from the light/dark experienced by the eye. What I would like though, is to give our municipality concrete data on light pollution over the years. 

"What I would like though, is to give our municipality concrete data on light pollution over the years."

 

I think you many be overthinking this. You may not need or be able to find historical data of light pollution variations over the years to present to your particular municipality nor would you likely need it.

 

Watch the following video on light pollution produced by a municipality in the LA County. Pay particular attention to the light pollution map at approximately 2:00 and the color temps at around 6:00 or thereabouts.

 

https://www.youtube....dStuAKJPZs&t=4s

[PEterW]

All photometeic sensors have some degree of error in their colour response… they never exactly match the human eye colour response (which is not exactly known as it was determined from a small number of people many years ago and isn’t the sort of thing you can repeat easily).
Lights with drastically different colour contents (tungsten, fluorescent, LED etc) will have different errors, making it harder to deal with.
Many of my local streetlights are LED, but their fittings are very good, so the sky looks darker and measures as such (though you need a good transparent night to show this). The variability in the sky conditions adds a good deal to the measurements. The warmer LED will likely have less error. We really need to keep pushing for lighting to be only used where necessary and to only light what is necessary, this will reduce the pollution a good deal already. It would be nice to have measurements to show things changing, It is a pity that trends are not as easy to determine as they might be.

Peter

[Ron359]

I doubt anyone thinks an SQM is as accurate as an atomic clock and the changeover to LED street lighting for many cities and towns is certainly a more recent makeover than just a decade ago, let alone 20 years.

 

That said, I'm not going down the same path again with you on the usage of an SQM since we've been back and forth over it on prior threads.

 

For anyone else who truly wants an in depth review of the the methods used to assess the brightness of the night sky, including the SQM, see the link for the pdf by Dr Barentine:

 

https://www.research..._and_Monitoring

Since you have no inclination to correct your false assertions in further discussion.  You can quibble and question the data and experience of pro-astronomers all you want.  But opinions are simply not facts or science.  

 

For the record... Its simply a matter of facts that the SQMs were designed well before LED public lighting became common and added to the levels of LP.  Thats why it was designed to "minic" the response of the human eye with a filter added.  They have never announced any plans to change the filter.  The filter information has been posted in the FAQs page of the Unihderon's website for many years...If you look at the links they provide for the technical data in the FAQ they are dated 2008 and 2005.

 

  As to the accuracy and precision I have 'interjected' the facts as stated in the manual on many CNs discussions where users are fretting or even arguing about differences of readings in the tenths of sq mag. per arc sec.  I'm not going to go back and count the number of posts I've added the 'caution' about it being stated in the SQM instruction manual.  

 

Here is the copied quote and link from the FAQ about the filter:   If you want to know exactly how many years it goes back, and became a 'concern' because of LEDs light output,  you'll have to ask Unihedron. You are not doing the 'amateur' CNs LP community any favors with your assertions or inaccuracies. I have largely 'dropped out' of the CNs because of all the now 'tiresome misinformation' I constantly read here. 

 

http://www.unihedron...sky/faqsqml.php

 

FAQ - "Have you measured the spectral response of the detector with the IR rejection filter, and how closely does it match the response of the human eye?We haven't measured the spectral response curve ourselves, but the sensor manufacturer has. It is very close to that of the human eye. The Hoya CM-500 filter cuts off the entire infrared part of the spectrum. The response is that of the "clear" line in Figure 2 of the TCS230 datasheet (which is for a different sensor in the TAOS line).
The combined spectral response compared to other standards is shown in this Night Sky Photometry with Sky Quality Meter report in Fig 12, on page 6.""  

Edited by Ron359, 30 October 2024 - 12:55 PM.

[RLK1]

Since you have no inclination to correct your false assertions in further discussion.  You can quibble and question the data and experience of pro-astronomers all you want.  But opinions are simply not facts or science.  

 

For the record... Its simply a matter of facts that the SQMs were designed well before LED public lighting became common and added to the levels of LP.  Thats why it was designed to "minic" the response of the human eye with a filter added.  They have never announced any plans to change the filter.  The filter information has been posted in the FAQs page of the Unihderon's website for many years...If you look at the links they provide for the technical data in the FAQ they are dated 2008 and 2005.

 

  As to the accuracy and precision I have 'interjected' the facts as stated in the manual on many CNs discussions where users are fretting or even arguing about differences of readings in the tenths of sq mag. per arc sec.  I'm not going to go back and count the number of posts I've added the 'caution' about it being stated in the SQM instruction manual.  

 

Here is the copied quote and link from the FAQ about the filter:   If you want to know exactly how many years it goes back, and became a 'concern' because of LEDs light output,  you'll have to ask Unihedron. You are not doing the 'amateur' CNs LP community any favors with your assertions or inaccuracies. I have largely 'dropped out' of the CNs because of all the now 'tiresome misinformation' I constantly read here. 

 

http://www.unihedron...sky/faqsqml.php

 

FAQ - "Have you measured the spectral response of the detector with the IR rejection filter, and how closely does it match the response of the human eye?We haven't measured the spectral response curve ourselves, but the sensor manufacturer has. It is very close to that of the human eye. The Hoya CM-500 filter cuts off the entire infrared part of the spectrum. The response is that of the "clear" line in Figure 2 of the TCS230 datasheet (which is for a different sensor in the TAOS line).
The combined spectral response compared to other standards is shown in this Night Sky Photometry with Sky Quality Meter report in Fig 12, on page 6.""  

"Since you have no inclination to correct your false assertions in further discussion.  You can quibble and question the data and experience of pro-astronomers all you want.  But opinions are simply not facts or science."

 

That's precisely the kind of response I was expecting and it's approaching those that have succeeded in having a thread locked more than a time or two or three. Furthermore,  I'm not quibbling with pro-astronomers here and I'm not questioning "facts."

 

Frankly, what are you even talking about? You offered up the statement that the SQM lacked blue sensitivity: "It's been well known,  because they have had the information on their website for at least 20 years."

I didn't disagree with that but I pointed out that many cities and towns haven't switched over to blue emitting LEDs except in the last decade and likely more recently than that so the lack of blue sensitivity of an SQM wasn't as much of an issue as it is in more recent times with the changes in lighting technologies.

 

You also seem unwilling to acknowledge the fact that SQMs are still quite effective in dark skies wherein LEDs are not present , i.e. in the so-called bortle 1 or 2 regions. While I'm not a fan of the bortle scale, there are still many of those noted as such by the CSC in a number of states...

Edited by RLK1, 30 October 2024 - 12:58 PM.

[Ron359]

"Since you have no inclination to correct your false assertions in further discussion.  You can quibble and question the data and experience of pro-astronomers all you want.  But opinions are simply not facts or science."

 

That's precisely the kind of response I was expecting and it's approaching those that have succeeded in having a thread locked more than a time or two or three. Furthermore,  I'm not quibbling with pro-astronomers here and I'm not questioning "facts."

 

Frankly, what are you even talking about? You offered up the statement that the SQM lacked blue sensitivity: "It's been well known,  because they have had the information on their website for at least 20 years."

I didn't disagree with that but I pointed out that many cities and towns haven't switched over to blue emitting LEDs except in the last decade and likely more recently than that so the lack of blue sensitivity of an SQM wasn't as much of an issue as it is in more recent times with the changes in lighting technologies.

 

You also seem unwilling to acknowledge the fact that SQMs are still quite effective in dark skies wherein LEDs are not present , i.e. in the so-called bortle 1 or 2 regions. While I'm not a fan of the bortle scale, there are still many of those noted as such by the CSC in a number of states...

The accuracy and precision of the SQM stated in the manual affects the readings and especially  "interpretations" of the readings regardless if its a Bortle 1 or middle of the city reading.  There are no 'caveats" given for correcting readings from one level of LP to another, LEDs or Na vapor LP or not.  

 

In my reading of posts in this forum, the most 'argued' readings and what they mean seem to come from those using them outside the brightest zones.   My only caution and assertion is to not 'argue' or debate over tenths of readings, because the accuracy and precision of a tenth is simply not there.  This is also proven out in several 'pro-papers' linked in the website and other pro-publications. And there are so many 'user' variables, the SQM readings should be used to give you a 'general' idea of changes or comparison from one zone to another.  Unfortunately the conversion scale is finer than it should be.  Especially given the "fact" that the sensor is a 'simple "photographic light meter" sensor designed and used for measuring lumens of bright daylight in  tens of thousands of lumens,  for daylight film photography back in the 80's or 90s.  They even state they've never measured the spectral response themselves.   The NIST standard they claim for accuracy of the SQM, is only for that NIST tested "light meter" sensor itself, as sold for photography.  Its not some 'high tech' CCD, CMOS sensor designed for extremely low light astronomy light levels.  The conversion to almost 0 lumens for night sky use,  is done with an algorithm they 'designed.'  Those are more "facts" you could learn by reading the information on their website.  

 

And Yes, you were questioning the  very statements of facts  I posted that I heard many times from a pro-astronomer (who took many days and hours out of his personal time to promote LP control with IDA in its early days, for the public and 'amateurs'. Even testifying before our state legislature and encouraging others to testify.) I worked with him on LP issues for many years.   So you are telling me the professional (who had worked on Hubble imaging projects, as well as 'classic' astro-physics of certain type of variable stars),  I worked with was 'full of it.'  

Edited by Ron359, 30 October 2024 - 01:54 PM.

[Sebastian_Sajaroff]

IMHO, those maps have no value.
They’re either outdated or irrealistic.
Best solution is to take a look at recent satellite photos or just assume that anything within 50 miles of a city or major industrial site will be light polluted.

[RLK1]

The accuracy and precision of the SQM stated in the manual affects the readings and especially  "interpretations" of the readings regardless if its a Bortle 1 or middle of the city reading.  There are no 'caveats" given for correcting readings from one level of LP to another.  

 

In my reading of posts in this forum, the most 'argued' readings and what they mean seem to come from those using them outside the brightest zones.   My only caution and assertion is that don't argue over tenths of readings because the accuracy and precision of a tenth is simply not there.  And there are so many user' variables, the SQM readings should be used to give you a 'general' idea of changes or comparison from one zone to another.  Unfortunately the conversion scale is finer than it should be.  Especially given the "fact" that the sensor is a simple "photographic light meter" sensor designed and used for measuring lumens of bright daylight in  tens of thousands of lumens,  for daylight film photography back in the 90s.  They even state they've never measured the spectral response themselves.   The NIST standard they claim for accuracy of the SQM, is only for that NIST tested "light meter" sensor itself,  not some 'high tech' CCD, CMOS sensor for low light astronomy light levels.  The conversion to almost 0 lumens for night sky use,  is done with an algorithm they 'designed.'  Those are more "facts" you could learn by reading the information on their website.  

 

And Yes, you were questioning the  very statements of facts  I posted that I heard many times from a pro-astronomer I worked with on LP issues for many years.   So you are telling me the professional (who had worked on Hubble imaging projects, as well as 'classic' astro-physics of certain type of variable stars),  I worked with was 'full of it.'  

"And Yes, you were questioning the  very statements of facts  I posted that I heard many times from a pro-astronomer I worked with on LP issues for many years.   So you are telling me the professional (who had worked on Hubble imaging projects, as well as 'classic' astro-physics of certain type of variable stars),  I worked with was 'full of it.'

 

Again, what are you even talking about?! Don't put words in mouth: I never said someone you worked with was:"full of it." 

And, in regards to questioning various views on light pollution, researchers, whom I've cited in prior threads along this line of discussion, have disagreements with the methods used to evaluate light pollution and sky brightness. But that doesn't mean you become the arbiter of who is correct and who isn't.

 

You've already argued about the accuracy of the SQM with other posters in this thread. There's no need to rehash it again with me.

[RLK1]

IMHO, those maps have no value.
They’re either outdated or irrealistic.
Best solution is to take a look at recent satellite photos or just assume that anything within 50 miles of a city or major industrial site will be light polluted.

I disagree with that particularly with respect to the OP's statement of "What I would like though, is to give our municipality concrete data on light pollution over the years."

 

Light pollution maps would likely make much more sense to officials in a municipality than satellite data. Additionally, maps do get updated from time to time so they can remain relevant. I haven't checked them for historical changes over time but I suppose it's possible there's a record or archive with some of them.

[mountain monk]

I observe in sites ranging from 21.5+, at home to 21.9+ NE of Jackson, to 22.00 mpsas sites in Yellowstone NP and several wildlife refuges in SW Montana. I have been taking SQM reading at those areas for over a decade and they are often close to DaveL’s most recent map. The more esoteric aspects of this discussion have little practical use for this amateur. At best, a kerfuffle.

 

Dark skies.

 

Jack

Edited by mountain monk, 30 October 2024 - 05:31 PM.

[Ron359]

"And Yes, you were questioning the  very statements of facts  I posted that I heard many times from a pro-astronomer I worked with on LP issues for many years.   So you are telling me the professional (who had worked on Hubble imaging projects, as well as 'classic' astro-physics of certain type of variable stars),  I worked with was 'full of it.'

 

Again, what are you even talking about?! Don't put words in mouth: I never said someone you worked with was:"full of it." 

And, in regards to questioning various views on light pollution, researchers, whom I've cited in prior threads along this line of discussion, have disagreements with the methods used to evaluate light pollution and sky brightness. But that doesn't mean you become the arbiter of who is correct and who isn't.

 

You've already argued about the accuracy of the SQM with other posters in this thread. There's no need to rehash it again with me.

I'm pointing out your assertion I was not considering that SQMs are used in Bortle 1 or dark areas so LED LP is 'irrelevant' to the readings is 'inaccurate' simply because the accuracy and precision of the SQM has no way to distinguish the wavelength of the lightl other than to be blind to the UV-blue range.  The accuracy of + or -10% of the reading,  is exactly same in any zone,  and hence a dark sky zone reading is just as accurate or inaccurate as the reading in the middle of a city.  And when you say I'm wrong about the filter cutoff of UV,  I'm not quoting you, I'm reading between the lines to what you're really telling me.

 

 I am not the arbiter of anyone,,  Since you and a few others seem ignorant of it,  I am simply pointing out what Unihedron's own website says and they provides the links to the research of some they find relevant that answer questions about the SQM. Reading cures most ignorance. 

Edited by Ron359, 30 October 2024 - 03:17 PM.

[Ron359]

I observe in sites ranging from 21.5+, at home to 22.9+ NE of Jackson, to 22.00 mpsas sites in Yellowstone NP and several wildlife refuges in SW Montana. I have been taking SQM reading at those areas for over a decade and they are often close to DaveL’s most recent map. The more esoteric aspects of this discussion have little practical use for this amateur. At best, a kerfuffle.

 

Dark skies.

 

Jack

You're mostly right.   The mag per arc sec scale goes to 22.0 (Unihedron's own statement of the meters algorithm limit) is 22.0  so +-10% is  2 tenths. ( ~0.2)).    And yes,  that is a large amount of relevant 'error' if your measuring in a dark site like Yellowstone. But largely irrelevant when compared to a bright suburb or city reading.   BTW  22.9 is waaayyyy off the accuracy lmit of the scale and likely a reading error either human or instrument calibration caused.

Edited by Ron359, 30 October 2024 - 03:29 PM.

[Ron359]

BTW - for those who care about the accuracy and precision of their Unihedron SQM readings,  heres a small challenge to test your critical thinking skills.   Find the apparent error in Unihedron's own FAQs about the IR cutoff filter used in the SQM.  And then point out why its in error.  

 

hint.  Its likely unintentional typo or perhaps a change in numbering system.   The link is in previous post #28.  The game is afoot.  ; )

Edited by Ron359, 30 October 2024 - 03:43 PM.

[RLK1]

I'm pointing out your assertion I was not considering that SQMs are used in Bortle 1 or dark areas so LED LP is 'irrelevant' to the readings is 'inaccurate' simply because the accuracy and precision of the SQM has no way to distinguish the wavelength of the lightl other than to be blind to the UV-blue range.  The accuracy of + or -10% of the reading,  is exactly same in any zone,  and hence a dark sky zone reading is just as accurate or inaccurate as the reading in the middle of a city.  And when you say I'm wrong about the filter cutoff of UV,  I'm not quoting you, I'm reading between the lines to what you're really telling me.

 

 I am not the arbiter of anyone,,  Since you and a few others seem ignorant of it,  I am simply pointing out what Unihedron's own website says and they provides the links to the research of some they find relevant that answer questions about the SQM. Reading cures most ignorance. 

"I'm pointing out your assertion I was not considering that SQMs are used in Bortle 1 or dark areas so LED LP is 'irrelevant' to the readings is 'inaccurate' simply because the accuracy and precision of the SQM has no way to distinguish the wavelength of the lightl other than to be blind to the UV-blue range."

 

What!? That makes little to no sense at all. I'm pointing out that the SQMs are effective in a dark sky environment given the lack of LED blue lighting emissions and obviously less so in a light polluted LED environment due to the lack of sensitivity in that portion of the spectrum. It should be equally obvious that if the uv-blue range of spectral emissions isn't a significant issue as in the case of what would be reportedly encountered in bortle 1 or 2 environment, then it it really doesn't matter whether or not the unit is blind to those emissions if the emissions aren't there in the first place. It does, of course, become more relevant if those emissions escape detection by an sqm in a more light polluted environment.

 

You've already argued the accuracy issue of SQMs with other posters in this thread. I've posted that in my prior post but you persist in doing the same again and again and denigrate someone you disagree with as "ignorant."

 

I had already contacted unihedron and asked for a clarification which I posted in a thread at the time and again in this thread in post #27. So both they and I and hopefully others can understand it in the context of these kinds of discussions. Their response seems clear to me in regards to the issue and what can be done about for those who wish to experiment with their own filters.

 

Beyond that, I'll include Dr Bartentine's description from a citation in this thread for those who prefer an unbiased review:

 

"Single-channel devices are patterned on photoelectric photometers used by astronomers for almost a century. These devices, such as the popular Sky Quality Meter (SQM; 87,88), rely on simple and well-understood physics, requirelittle electric current to operate, and are usually small enough to be easily portable. They typically employ light-to-frequency (LTF) converters whose output is a signal pulse stream, the frequency of which is linearly proportional to received light intensity. Their light response is determined in the laboratory,with on-board lookup tables relating measured frequency to light intensity tied to calibrated light sources. Since the response of LTF converters is also sensitive to ambient operating temperature, sensing of the air temperature is required to properly correct the measured frequency. This is usually done onboard the measurement device."

 

"Single-channel devices have a number of advantages, including ease of use;portability; a physically simple sensing mechanism; temperature compensation; good repeatability; rapid capture and display of data; and a relatively long historical record of use. However, there are certain drawbacks to these devices. In order to sense a sufficient amount of light to yield a measurable signal, they must integrate it over a relatively large solid angle. They offerlittle meaningful spatial resolution in most applications, making them generally unsuitable for monitoring the behavior of light domes near the horizon. Lastly, there are differences among commercially available devices in terms of photometric passbands that complicate comparison of results among different device types."

 

https://www.research..._and_Monitoring

[mountain monk]

Ron,

 

Thanks for the correction. I changed it to 21.9 mpsas.

 

Dark skies.

 

Jack

[mr.otswons]

I disagree with that particularly with respect to the OP's statement of "What I would like though, is to give our municipality concrete data on light pollution over the years."

 

Light pollution maps would likely make much more sense to officials in a municipality than satellite data. Additionally, maps do get updated from time to time so they can remain relevant. I haven't checked them for historical changes over time but I suppose it's possible there's a record or archive with some of them.

Just for the record, I'm not the OP 

 

And the maps, both lightpollution.info and their newest(?) project lighttrends.lightpollutionmap.info give great charts to show municipality.

 

The one on the top is from lightpollution.info with 20 km radius from my homestead, and the one on the bottom is a little further out from lighttrends.lightpollutionmap.info

 

A clear increase by 3.63% per year from 2012 and 6.39% from the bigger picture.

 

Not sure if you meant going back even further by "historical changes over time"

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Edited by mr.otswons, 30 October 2024 - 05:48 PM.

[RLK1]

Just for the record, I'm not the OP 

 

And the maps, both lightpollution.info and their newest(?) project lighttrends.lightpollutionmap.info give great charts to show municipality.

 

The one on the top is from lightpollution.info with 20 km radius from my homestead, and the one on the bottom is a little further out from lighttrends.lightpollutionmap.info

 

A clear increase by 3.63% per year from 2012 and 6.39% from the bigger picture.

 

Not sure if you meant going back even further by "historical changes over time"

"Just for the record, I'm not the OP"

 

Thanks for the clarification. At any rate in response to your statement of "Not sure if you meant going back even further by "historical changes over time":

 

I'd think what you've noted in your post would be adequate but the answer really depends upon you and what you think the municipality may want to see. 

 

The bottom line is there's an obvious increase over time with the trend going in the wrong direction, i.e worsening.

[Ron359]

 

Beyond that, I'll include Dr Bartentine's description from a citation in this thread for those who prefer an unbiased review:

 

 

"Single-channel devices have a number of advantages, including ease of use;portability; a physically simple sensing mechanism; temperature compensation; good repeatability; rapid capture and display of data; and a relatively long historical record of use. However, there are certain drawbacks to these devices. In order to sense a sufficient amount of light to yield a measurable signal, they must integrate it over a relatively large solid angle. They offerlittle meaningful spatial resolution in most applications, making them generally unsuitable for monitoring the behavior of light domes near the horizon. Lastly, there are differences among commercially available devices in terms of photometric passbands that complicate comparison of results among different device types."

 

https://www.research..._and_Monitoring

Once again,  because of your bias 'blindly' believing they are infallible instruments,  you miss my key points about SQM limitations  - even from your own posted reference papers author in his last sentence of his review.  

 

"They offerl little meaningful spatial resolution in most applications, making them generally unsuitable for monitoring the behavior of light domes near the horizon. Lastly, there are differences among commercially available devices in terms of photometric passbands that complicate comparison of results among different device types."  I've added the bold and underlines so no one misses the points.  

 

 In other words comparing their data to a satellite' broad spatial data - the topic of this OP - is comparing apples to oranges, especially for monitoring change of LP through time.  Thanks for making my point with that paper.  It is unfortunate most amateurs can't afford the other types he goes on to review in the paper.   Clear, dark skies.   Do the best with what you have.   But don't pretend its more than what it is. 

Edited by Ron359, 30 October 2024 - 08:23 PM.

[Ron359]

Just for the record, I'm not the OP 

 

And the maps, both lightpollution.info and their newest(?) project lighttrends.lightpollutionmap.info give great charts to show municipality.

 

The one on the top is from lightpollution.info with 20 km radius from my homestead, and the one on the bottom is a little further out from lighttrends.lightpollutionmap.info

 

A clear increase by 3.63% per year from 2012 and 6.39% from the bigger picture.

 

Not sure if you meant going back even further by "historical changes over time"

Nice to see the variations and actual data points, with an actual statistical analysis showing the statistical trend.  The variations in data points would 'drive' a 'typical amateur' who only sees the disparate values, crazy.