Author Topic: LP Map (new to us)  (Read 226 times)

Brenton Crosby

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Re: LP Map (new to us)
« Reply #15 on: January 31, 2018, 11:50:49 AM »
Thanks. New to me too.And yep the amount of stray photons represents a considerable economic loss as well. I am very lucky to live were I do, in the black so to speak.

Artavius Murphy

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Re: LP Map (new to us)
« Reply #16 on: February 02, 2018, 08:07:09 PM »
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So much wasted energy. Sad.

NO! So much wasted money that could be spent elsewhere. That's sad.

Justin Prasad

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Re: LP Map (new to us)
« Reply #17 on: February 02, 2018, 08:25:27 PM »
Ahh isn't that nice!  They decided to light up my spot on the map so I could see it better!

ermaudyvi

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Re: LP Map (new to us)
« Reply #18 on: February 02, 2018, 08:54:37 PM »
I skimmed the background on the sources and what these maps are showing, and played with them in Photoshop. The blue-marble is from satellite data. It is simply a composite view of the earth from processed in-orbit images. The original output scale is 0-63 gray, and many pixels are saturated (more pixels than the lightpollution.it lp maps). So Abilene downtown night skies show to be as bright as downtown Dallas - I think this is inaccurate. Black at blue-marble covers roughly the same area as gray, light gray, and blue combined at lightpollution.it. That translates roughly to natural night illumination levels up to 3x brighter than that, due to light pollution. White at blue-marble corresponds roughly to white and red at lightpollution.it.That leaves roughly 60 shades of gray to correspond to the green, yellow, and orange colors (which each cover a range of 3x in brightness). If the grayscale is linear in that range, green is about 2-20, yellow is about 20-40, and orange about 40-60.BTW, the distinction between gray and light gray at lightpollution.it is not very useful for selecting an observing site. The difference is only 1% (according to their paper). The biggest difference that makes lightpollution.it more useful for amateur astronomers is that they model the effects of light pollution (for some maps). Adding scattering / diffusion gives a very different picture, showing how the proximity of large light sources has a negative impact on sky darkness. That is, according to blue-marble, you don't have to go nearly as far from downtown to get to dark skies as lightpollution.it. I think the latter must be much more accurate and useful.

belohalcu

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Re: LP Map (new to us)
« Reply #19 on: February 03, 2018, 01:52:38 PM »
I get depressed looking at these maps.   40 years ago I could see the milky way from my home in Portland, OR...now, I cant see anything from almost anywhere....and now I'm into astronomy...good timing!

vistadussi

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Re: LP Map (new to us)
« Reply #20 on: February 04, 2018, 10:53:48 AM »
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So much wasted energy. Sad.

That's exactly the kind of thing you can't judge unless you know how the maps are calibrated. A certain degree of light pollution is inevitable; I wouldn't call lighting downtown sidewalks a waste of energy. And while any society that relies on private automobiles for transportation is inherently wasteful, the headlights that cause light pollution are only a tiny fraction of that waste.

Depending how the lighting is portrayed, I could easily make a place with superb full-cutoff lighting look terrible or make a place with atrociously wasteful lighting look great.

Jon Venning

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Re: LP Map (new to us)
« Reply #21 on: February 08, 2018, 06:37:19 PM »
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I wouldn't call lighting downtown sidewalks a waste of energy...Depending how the lighting is portrayed, I could easily make a place with superb full-cutoff lighting look terrible or make a place with atrociously wasteful lighting look great.
It's how you use the fixtures that makes the difference. Light fixtures that light up the sky as well as the intended areas most certainly wast both money and energy.

James Gruber

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Re: LP Map (new to us)
« Reply #22 on: February 08, 2018, 09:49:06 PM »
Hootie Hoo! I have a public access black zone 15 miles away! Even in the backyard I'm only gray and see 6+ mag skies. I'll count myself as fortunate. On the Dark Sky Finder the same sites are yellow and green.

Eric Lara

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Re: LP Map (new to us)
« Reply #23 on: February 09, 2018, 02:32:58 AM »
Great map. Spot the deserts lol

Jim Parker

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Re: LP Map (new to us)
« Reply #24 on: February 09, 2018, 10:31:47 AM »
TY Deranged...we didn't know about

http://www.lightpoll...it/indexen.html