Author Topic: What is the worst light pollution source?  (Read 415 times)

ebalared

  • Active Astronomer
  • ***
  • Posts: 131
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #15 on: January 12, 2018, 11:33:36 AM »
Quote
Quote

LED's are the current politically correct savior of the planet but as far as I know the actual efficiency of LED's has not yet passed that of high or low pressure sodium lights. In fact I am not sure that LED's have passed high efficiency florescents or metal halide lights.

From what I have read LED lights are not at the point where either cost or efficiency merits wholesale adoption for replacement of street lights.


The above statement is a seriously inaccurate misunderstanding of the relative efficiencies of LEDs vs the other named light sources, both in terms of energy and cost. The reasons LEDs are more efficient light sources are closely tied to why they are potentially both boon and bane for astronomy (back to this in a minute). Rather than nebulously saying "I read this somewhere", here's a couple of links to enlightenment on the subject:
1) For a good self-contained technical explanation (requires some modest scientific literacy, but not a physics degree):
Comparison of LED v Other light sources including HID
2) For a comprehensive overview of the characteristics and advantages vs disadvantages of various types of street lights:
Street lighting technology comparison

Here's the probable basis for your claim that LEDs are a less efficient source than high or low pressure sodium lights or metal halide lights, extracted from a chart you'll find in the first chart I cited above.

Light Source:         Lumens/Watt
Low-Pr Sodium       130
High-Pr. Sodium       110
Metal Halide          90
T8 Fluorescent(3000K) 78
LED                100

Measured in Lumens/Watt, LEDs would indeed seem to fall short of sodium lights by 10 to 30%. However (and here's where relevant tie-back to astronomy begins) - what actually does a "lumen" represent? First, lumens are a measure of the total light produced by a lamp, without taking into consideration how efficiently it's directed. Because sodium lights emit in a 360 degree sphere vs LEDs being directionally limited, raw lumens/watt is a misleading measure. (That is the characteristic of LEDs that is potentially good for astronomy). Also, lumens are a photopic measure (response by cones responsible for color vision), yet sodium lights emit most of their light within a narrow spectrum (good for ability of astronomers to filter out those wavelengths), but actual street lighting conditions are in the low-medium range of mesopic (mixed rods and cones) vision, which the full visible spectrum output of LEDs covers more effectively (and accurately) - hence pupil lumens/watt is a better measure (bad for ability of astronomers to filter out LEDs). I'll refer you to the first article for the articulate in-depth explanation of what "pupil lumens" is and why it's a better measure of mesopic vision lighting effectiveness, but measured this way:

Light Source:         Pupil Lumens/Watt
Low-Pr Sodium 29.9
High-Pr. Sodium 68.2
Metal Halide134.1
T8 Fluorescent(3000K) 87.89
LED 200

...which is why an LED streetlight can produce the same effective amount of light for lower wattage than low or high-pressure sodium lights and so on, AND with much more accurate color rendition (meaning people can see things better with LEDs, even using less raw wattage). Unlike sodium street lights, LED street lights can be adjusted to be brighter or dimmer (less energy), instead of same brightness e.g. at 3am when few people are about. (Good for astronomy, if the utility intelligently uses this feature).
This explains many things - the most important being why LED lights blind you when you see them. They are usually bought by the municipalities based on lumen replacement - right off the bat at least twice as much as required as the upwards lighting is gone. Then your explanation that our eyes see this light between 2x and 6x better than the alternatives. Thanks for such clear information. So if I understand all this correctly, when you replace a HP sodium light in a cobra fixture, you only need 1/6 of the power to light up the ground below: 0.5 (for no loss upwards) X 68.2 / 200.

I'll be talking to our municipal administrators shortly.

Eric

Andre Ransom

  • Active Astronomer
  • ***
  • Posts: 106
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #16 on: January 13, 2018, 04:11:42 AM »
Quote
Quote

Quote

LED's are the current politically correct savior of the planet but as far as I know the actual efficiency of LED's has not yet passed that of high or low pressure sodium lights. In fact I am not sure that LED's have passed high efficiency florescents or metal halide lights.

From what I have read LED lights are not at the point where either cost or efficiency merits wholesale adoption for replacement of street lights.


The above statement is a seriously inaccurate misunderstanding of the relative efficiencies of LEDs vs the other named light sources, both in terms of energy and cost. The reasons LEDs are more efficient light sources are closely tied to why they are potentially both boon and bane for astronomy (back to this in a minute). Rather than nebulously saying "I read this somewhere", here's a couple of links to enlightenment on the subject:
1) For a good self-contained technical explanation (requires some modest scientific literacy, but not a physics degree):
Comparison of LED v Other light sources including HID
2) For a comprehensive overview of the characteristics and advantages vs disadvantages of various types of street lights:
Street lighting technology comparison

Here's the probable basis for your claim that LEDs are a less efficient source than high or low pressure sodium lights or metal halide lights, extracted from a chart you'll find in the first chart I cited above.

Light Source:         Lumens/Watt
Low-Pr Sodium       130
High-Pr. Sodium       110
Metal Halide          90
T8 Fluorescent(3000K) 78
LED                100

Measured in Lumens/Watt, LEDs would indeed seem to fall short of sodium lights by 10 to 30%. However (and here's where relevant tie-back to astronomy begins) - what actually does a "lumen" represent? First, lumens are a measure of the total light produced by a lamp, without taking into consideration how efficiently it's directed. Because sodium lights emit in a 360 degree sphere vs LEDs being directionally limited, raw lumens/watt is a misleading measure. (That is the characteristic of LEDs that is potentially good for astronomy). Also, lumens are a photopic measure (response by cones responsible for color vision), yet sodium lights emit most of their light within a narrow spectrum (good for ability of astronomers to filter out those wavelengths), but actual street lighting conditions are in the low-medium range of mesopic (mixed rods and cones) vision, which the full visible spectrum output of LEDs covers more effectively (and accurately) - hence pupil lumens/watt is a better measure (bad for ability of astronomers to filter out LEDs). I'll refer you to the first article for the articulate in-depth explanation of what "pupil lumens" is and why it's a better measure of mesopic vision lighting effectiveness, but measured this way:

Light Source:         Pupil Lumens/Watt
Low-Pr Sodium 29.9
High-Pr. Sodium 68.2
Metal Halide134.1
T8 Fluorescent(3000K) 87.89
LED 200

...which is why an LED streetlight can produce the same effective amount of light for lower wattage than low or high-pressure sodium lights and so on, AND with much more accurate color rendition (meaning people can see things better with LEDs, even using less raw wattage). Unlike sodium street lights, LED street lights can be adjusted to be brighter or dimmer (less energy), instead of same brightness e.g. at 3am when few people are about. (Good for astronomy, if the utility intelligently uses this feature).
This explains many things - the most important being why LED lights blind you when you see them. They are usually bought by the municipalities based on lumen replacement - right off the bat at least twice as much as required as the upwards lighting is gone. Then your explanation that our eyes see this light between 2x and 6x better than the alternatives. Thanks for such clear information. So if I understand all this correctly, when you replace a HP sodium light in a cobra fixture, you only need 1/6 of the power to light up the ground below: 0.5 (for no loss upwards) X 68.2 / 200.

I'll be talking to our municipal administrators shortly.

Eric
Come over to North Bay and have a look at night, the light dome has been reduced by 80% and would be 100% if the highways ministry and local businesses would retrofit their illumination systems. The street light intensity is a lot softer on the eyes because of it's directional projection but visually is excellent and contrary to what many say the wild life sure aren't falling over due to any detrimental effects, all of this is relatively new and I think has to be given a chance as this technology becomes more and more refined / improved as it sure can't be any worse than what we have / had. If you can work the numbers and show the town authorities they might be convinced but having said that because of their close proximity to the Bay maybe they already are aware and are looking into it already ? The problem in Quebec is that they have so much power generation / cheap power that maybe the provincial government aren't pushing these type of upgrade programs through retrofit grants. / subsidies etc. ? Not yet anyway !   LW

Paul Kasilowski

  • Jr. Astronomer
  • **
  • Posts: 94
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #17 on: January 15, 2018, 10:07:59 AM »
You are right - North Bay really has done well. Really noticeable when driving east on Trout Lake Road. No glare anywhere on the hillside although lots of houses.
The difference in electricity rates between Ontario and Quebec has pushed the LEDs faster in ON than QC. Nonetheless there is an incentive program from Hydro-Quebec. Outdoor lamp replacement is still cheaper than new dams and any form of green energy. Conservation is always the better way...
Some outdoor tourist-oriented towns are responding more quickly. Here in Témiscaming the old lights are getting replaced as they fail.

faubloginac

  • Active Astronomer
  • ***
  • Posts: 127
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #18 on: January 18, 2018, 12:19:41 AM »
Quote
You are right - North Bay really has done well. Really noticeable when driving east on Trout Lake Road. No glare anywhere on the hillside although lots of houses.
The difference in electricity rates between Ontario and Quebec has pushed the LEDs faster in ON than QC. Nonetheless there is an incentive program from Hydro-Quebec. Outdoor lamp replacement is still cheaper than new dams and any form of green energy. Conservation is always the better way...
Some outdoor tourist-oriented towns are responding more quickly. Here in Témiscaming the old lights are getting replaced as they fail.

Hopefully that change won't take too long to complete. The times I talked to some town officials they sure didn't seem the type to sit on their hands.  LW

caheadhilldea

  • Active Astronomer
  • ***
  • Posts: 129
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #19 on: January 18, 2018, 05:37:36 AM »
Breaking News: in Témiscaming, Canada scientists are examining why local street lighting is failing at an astronomical rate. Local astronomers are examining why scientists think this is a problem.......

corloconre

  • Active Astronomer
  • ***
  • Posts: 124
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #20 on: January 21, 2018, 12:54:22 AM »
Quote
Breaking News: in Témiscaming, Canada scientists are examining why local street lighting is failing at an astronomical rate. Local astronomers are examining why scientists think this is a problem.......

Especially at an ' astronomical rate ' ! I didn't even know you lived in Temiscaming ? LOL !

asagnata

  • Active Astronomer
  • ***
  • Posts: 126
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #21 on: January 21, 2018, 01:02:26 AM »
Quote
Breaking News:  in Témiscaming, Canada scientists are examining why local street lighting is failing at an astronomical rate.  Local astronomers are examining why scientists think this is a problem.......
Irony times C^2 (the speed of light © squared is a huge number).

Timothy Moody

  • Active Astronomer
  • ***
  • Posts: 121
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #22 on: January 21, 2018, 04:20:00 AM »
Quote
Breaking News: in Témiscaming, Canada scientists are examining why local street lighting is failing at an astronomical rate. Local astronomers are examining why scientists think this is a problem.......


ifaclidis

  • Active Astronomer
  • ***
  • Posts: 117
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #23 on: January 23, 2018, 10:20:01 AM »
In this part of the planet, the biggest source of light pollution by a huge amount is downhill ski resorts. 12 miles south of me is a medium-sized ski area. Unfortunately for me, the area faces north. All night long, around 250 HP Sodium and Merc Vapor lights shine downward onto the snow, and reflect upward to light the cosmos.

The lighting provides advertising, allows the night snowmaking/grooming crew to see to work, and has to be on to run the snowguns, because there are several miles of heavy-gauge wire, and unfortunately only one feed per side of each run, so both guns and lights are on the same wires.

Their electric bill was huge, as you can imagine, so in the last several years, they have erected a large wind generator and a bunch of photovoltaics, they are approaching net-zero electricity costs. If it's free anyhow, let's hang another hundred lights!!

The Northeast has at least 100 downhill resorts, almost all of whom run the lights all night......

Grimarlon Warren

  • Active Astronomer
  • ***
  • Posts: 118
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #24 on: January 23, 2018, 11:52:05 AM »
Same problem here, sadly. And, of course, they tend to build ski resorts in remote places where it WAS dark. There are delicious ironies, though: some resorts have to pay Indians huge amounts $$$$ for tribal water so the resorts can run their snow making machines, there being (in general) less and less snow.

Dark skies.

Jack

quelesmawea

  • Active Astronomer
  • ***
  • Posts: 129
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #25 on: January 23, 2018, 01:55:53 PM »
Quote
....... The Northeast has at least 100 downhill resorts, almost all of whom run the lights all night......


I'll trade ya a dozen flaring gas frack'ing wells for one ski resort......

whoopsirode

  • Active Astronomer
  • ***
  • Posts: 120
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #26 on: January 23, 2018, 04:58:43 PM »
Quote
Quote

....... The Northeast has at least 100 downhill resorts, almost all of whom run the lights all night......


I'll trade ya a dozen flaring gas frack'ing wells for one ski resort......

Hard deal to pass up ! LOL !

selusmiystag

  • Active Astronomer
  • ***
  • Posts: 132
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #27 on: January 29, 2018, 11:56:32 PM »
LED street light have already replaced other forms in many cities in California. I read an article over one year ago that said San Diego (and I think LA) were going to convert ALL of their street lights to LEDs within about one year. Kind of makes you wonder how cities can afford such conversions given that they are supposed to be under very tight spending controls. I don't know whether both cities have completed the conversion, but it was supposed to happen very quick and be done by about now. I also live in a small city in southern CA and they also have many street lights that are LEDs (changed a year to two ago). Problem is, standard light pollution filters have absolutely no effect on the broad-band light produced by the LEDs. I've check filters using a light meter and the LED street light show no reduction (other than a slight neutral density change) while Sodium/Mercury lights are reduced by about 3 f-stops (the filter cuts about 85% of the emissions from the Sodium/Mercury lights).

spicomgeovio

  • Active Astronomer
  • ***
  • Posts: 125
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #28 on: January 30, 2018, 03:24:56 AM »
Probably they are getting some federal grant money, maybe on a 50/50 deal, to decrease energy consumption.

Aaron Maggot

  • Active Astronomer
  • ***
  • Posts: 132
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: What is the worst light pollution source?
« Reply #29 on: January 30, 2018, 04:14:21 AM »
LED is inevitable. The old streetlights are not even made any more. As Bill pointed out there's Fed $$ here, and major savings over time.

The possible good news is: LEDs are all shielded, and they can be dimmed, and even controlled from a central location, allowing for dimming after evening traffic goes down, etc. On the other hand, if local gov sees the reduced power cost as a way to increase brightness, we have a problem. At least in the town near me that is investigating changing, the town officials have expressed concern about the lights being too bright. The company that is pushing this told the town that they can adjust the brightness of each light (which is true). That still leaves the color issue, which the amateur astronomers and public observatory in the area intend to take up with the town boards.