Author Topic: Light pollution GIF 1950-2010  (Read 331 times)

mosretouless

  • Active Astronomer
  • ***
  • Posts: 133
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #15 on: January 13, 2018, 03:25:00 PM »
Quote
That may well explain why LP is less after midnight, at least in areas were the traffic gets far less late at night.
Indeed my own SQM logs for the past 5 years shows a marked drop after approx 23:00 until dawn (clear nights only - avoiding affects due to low clouds))

Grimarlon Warren

  • Active Astronomer
  • ***
  • Posts: 118
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #16 on: January 17, 2018, 11:36:55 PM »
Quote
<p class="citation">Quote....Obviously, the huge increase in car traffic since the 70s has also been a major effect. Car headlights are one of the very biggest sources of light pollution, probably exceeding even streetlights in outer suburbs.

That may well explain why LP is less after midnight, at least in areas were the traffic gets far less late at night. [/quote]

Not just less traffic, but fewer business lighting, at least from I've seen.  The three car dealers here in town where I live have lights that (mostly) go off after 11:00pm, and the two nearby gas stations with the more horrific lights ever also go off before or around that time.  That changes the sky quite significantly after 10 or 11 pm for me.  I would imagine in the locations where streetlights are being put on timers to go off after 12:00 midnight that there is a noticeable affect in those areas too, though I think that's a relatively new idea for many municipalities.

Zachary Patterson

  • Active Astronomer
  • ***
  • Posts: 126
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #17 on: January 20, 2018, 03:07:39 PM »
This makes me sick

chlorleifilwhirl

  • Active Astronomer
  • ***
  • Posts: 126
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #18 on: January 20, 2018, 11:38:43 PM »
Quote
<p class="citation">Quote<p class="citation">Quote....Obviously, the huge increase in car traffic since the 70s has also been a major effect. Car headlights are one of the very biggest sources of light pollution, probably exceeding even streetlights in outer suburbs.

That may well explain why LP is less after midnight, at least in areas were the traffic gets far less late at night. [/quote]

Not just less traffic, but fewer business lighting, at least from I've seen.  The three car dealers here in town where I live have lights that (mostly) go off after 11:00pm, and the two nearby gas stations with the more horrific lights ever also go off before or around that time.[/quote]

Absolutely. Sky brightness declines rapidly and steadily until around 11 p.m., and I have no doubt that this is one of the major causes.

However, it continues to decline more gradually until it flattens out around 2 or 3 a.m., and it's hard to think of any source that could explain that other than automobile headlights.

I will point out also that flying into a city at night, the two light sources that appear most prominent by far are streetlights and headlights. No doubt that's helped by the fact that the headlights are moving, and the eye-brain system is tuned to detect moving objects. But still, the brightness of headlights as seen from the air is unmistakable.

Headlights are also at the orientation that's most harmful -- pointing sideways, so they continue scattering light over a very long path.

rissubssimpsat

  • Active Astronomer
  • ***
  • Posts: 107
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #19 on: January 22, 2018, 08:34:29 PM »
As dramatic as the graphic is, I think it is a bit flawed, at least as my neck of the woods is concerned. As of today, in New Brunswick, there are only four areas labelled as red on the light pollution map, and those are just small dots. I would say the average for the whole area of the province is green at the very most, but probably blue. The graphic ends with the eastern part of the province as red and white, and the rest of the province as green.I know for a fact that this isn't going to happen in my lifetime. Here, if a city gets brighter due to increasing population, it is at the expense of another region of the province, which one could reasonably assume is getting dimmer (last one out dim the lights, sort of thing)...

Jay Cole

  • Active Astronomer
  • ***
  • Posts: 109
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #20 on: January 22, 2018, 09:31:36 PM »
Quote
Absolutely. Sky brightness declines rapidly and steadily until around 11 p.m., and I have no doubt that this is one of the major causes.

However, it continues to decline more gradually until it flattens out around 2 or 3 a.m., and it's hard to think of any source that could explain that other than automobile headlights.

I wonder if there is a way that motor vehicle headlights could be designed to use a polarized lens, so that light only goes downwards (even very slightly would help).  This could potentially have multiple benefits, not only contributing to better skies, but perhaps even reduce the glare experienced by drivers heading towards other vehicles' headlights.  I wonder if such a thing is not only technically feasible, but practical as well...?

breakinnocor

  • Active Astronomer
  • ***
  • Posts: 130
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #21 on: January 23, 2018, 01:20:08 AM »
Quote
so that light only goes downwards


This certainly would not work on dark roadways, when one has to watch ahead &amp; all around for deer, etc. at night.

Dave Jones

  • Active Astronomer
  • ***
  • Posts: 109
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #22 on: January 23, 2018, 07:09:11 AM »
Quote
<p class="citation">QuoteThat may well explain why LP is less after midnight, at least in areas were the traffic gets far less late at night.
Indeed my own SQM logs for the past 5 years shows a marked drop after approx 23:00 until dawn (clear nights only - avoiding affects due to low clouds)) [/quote]I live in white zone and best is between 1 and 4 in the morning that I able to see as faint as almost 4th mag! Few extra faint stars in Orion.

Darius Swick

  • Active Astronomer
  • ***
  • Posts: 115
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #23 on: January 23, 2018, 08:23:37 AM »
Quote
<p class="citation">Quote so that light only goes downwards


This certainly would not work on dark roadways, when one has to watch ahead &amp; all around for deer, etc. at night. [/quote]

I probably was not precise enough in what I meant.  I mean if the majority of the light is angle just slightly downwards towards the road, and well ahead of the vehicle.  Most headlights are already designed for the majority of light to go towards this area as it is.  But when it is foggy, for example, one can see how much light actually goes not just up, but WAY up from headlights.  I can recall seeing light reflecting off of tree branches when looking up through moon-roofs of some vehicles - do we need to see that high up, literally, almost overhead from the nose of the vehicle? 

I understand the need to look ahead, and there is nothing about polarizing the lenses that means the light would be diminished to the sides of the vehicle.  But how much of it needs to go up above the horizontal?  Can we make lenses that diminishes how much goes up, and so that there is only enough to maintain safety and sufficient visibility in that area?  I'm just throwing out some questions to see if we can look at ideas of better ways to design headlights - not compromise safety.

Rick Nocturnum

  • Active Astronomer
  • ***
  • Posts: 109
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #24 on: January 23, 2018, 11:43:24 AM »
Remember the old WWII movies, where for air-raid purposes vehicles were fitted with a type of metal cutoff shield to keep enemy aircraft from spotting the headlights? Something along those lines would probably be what is needed, although today vacuum-deposited aluminizing inside the lights' glass surfaces would perform the same function, and what would doubtless be used.The point is moot, however... although practical to a degree, as far as a method to reduce light pollution this is a non-starter on many levels. What <em class="bbc">would be almost as effective would be people reducing the number of trips they make in their vehicles by consolidating them. This may be forced upon people if the price of gasoline doubles or triples in the near future, although I'd much, <em class="bbc">much rather endure the light pollution, than the proximate cause of such a state of affairs.

Owen Khan

  • Active Astronomer
  • ***
  • Posts: 134
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #25 on: January 25, 2018, 05:21:44 PM »
Some HID headlights on cars have incredibly sharp cutoffs just a few degrees above the road. For example, I had an 06 Mazda MX-5 that had a flat edge across the top of the illuminated field, and in fact the field to the left of center had a lower cutoff to avoid blinding other drivers. The brights were incandescents, and had a typical cone-shaped field, illuminating areas higher above the road. It was nice to see the two combined like that. It will be interesting to see if HIDs see greater adoption. So, what wavelength is HID lighting, anyway?  I'm assuming it is not blackbody radiation.

Jon Venning

  • Active Astronomer
  • ***
  • Posts: 130
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #26 on: January 31, 2018, 01:34:33 AM »
Yeah the map shows all of Florida is basically red including my dark sky site which is in a blue zone

Miguel Alvarado

  • Active Astronomer
  • ***
  • Posts: 121
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #27 on: January 31, 2018, 10:46:12 AM »
I think this may be a projection for what LP will be like by 2050.

tioteyclasbeat

  • Active Astronomer
  • ***
  • Posts: 130
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #28 on: January 31, 2018, 12:33:27 PM »
Quote
I think this may be a projection for what LP will be like by 2050.
Given current trends, and taking into account humanity's demonstrated predilections, I believe chances are at least even that the LP map of 2050 will resemble this:

Attached Thumbnails

Tyler King

  • Active Astronomer
  • ***
  • Posts: 132
  • Activity:
    0%
  • Reputation: +0/-0
    • View Profile
Re: Light pollution GIF 1950-2010
« Reply #29 on: February 02, 2018, 04:21:04 PM »
You're a bundle of sunshine, Today.