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What are the mysterious light sources on light pollution maps?

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Re: What are the mysterious light sources on light pollution maps?

#11

Post by reaperducer »

rabuse wrote: post #4

I was looking at light pollution maps just the other day, trying to find places to do astro-photography, and was blown away by how much light pollution there is. Really sucks, because I'd have to drive about 90 minutes out to get into a dark zone.

Dark skies are so rare these days that remote towns in Colorado, Arizona, and Nevada promote themselves to stargazers.

Example: https://www.tonopahnevada.com/stargazing/

"In most cities you can see between 25-50 stars, in Tonopah you can see 7,000!"

Re: What are the mysterious light sources on light pollution maps?

#12

Post by yread »

amatecha wrote: post #8

Ah yeah, in the post's first "unknown light pollution" example, I figured it must be a greenhouse. I was driving through a relatively small town one time and was a bit freaked out by this ominous yellow glow off in the distance. Like, the whole sky was glowing [0]. I ended up driving out to try to find the source, and discovered it was a huge greenhouse/farm. Luckily not an extraterrestrial landing zone or so on ;) […

Yellow glow is understandable, but check out this purple one

https://www.cbc.ca/news/canada/windsor/not-northern-lights-g...

Re: What are the mysterious light sources on light pollution maps?

#13

Post by 3JPLW »

twic wrote: post #6

I flew through the night to Singapore once. I remember two very striking light sources. Firstly, oil well flares in the Middle East. The oil fields are in the middle of nowhere, so they're these huge orange-red blooms set in utter darkness. Secondly, Delhi. The city is brightly lit with streetlights. But there's a suburb (?) to the south, Faridabad, that's as brightly lit, but with a different, whiter, kind of lights…

Chicago has been slowly replacing its yellow sodium streetlamps with efficient LEDs that project down instead of up. They've been working block-by-block in a systematic way that you can see when you fly into the city at night. It's quite dramatic.

Re: What are the mysterious light sources on light pollution maps?

#15

Post by amatecha »

yread wrote: post #12
amatecha wrote: post #8

Ah yeah, in the post's first "unknown light pollution" example, I figured it must be a greenhouse. I was driving through a relatively small town one time and was a bit freaked out by this ominous yellow glow off in the distance. Like, the whole sky was glowing [0]. I ended up driving out to try to find the source, and discovered it was a huge greenhouse/farm. Luckily not an extraterrestrial landing zone or so on ;) […

Yellow glow is understandable, but check out this purple one https://www.cbc.ca/news/canada/windsor/not-northern-lights-g...

Ah yeah, that's exactly where I got the above photo from. The purple glow is ridiculous! At least the yellow is a little less "abrasive" and more natural-looking.

Re: What are the mysterious light sources on light pollution maps?

#16

Post by snazz »

yread wrote: post #12
amatecha wrote: post #8

Ah yeah, in the post's first "unknown light pollution" example, I figured it must be a greenhouse. I was driving through a relatively small town one time and was a bit freaked out by this ominous yellow glow off in the distance. Like, the whole sky was glowing [0]. I ended up driving out to try to find the source, and discovered it was a huge greenhouse/farm. Luckily not an extraterrestrial landing zone or so on ;) […

Yellow glow is understandable, but check out this purple one https://www.cbc.ca/news/canada/windsor/not-northern-lights-g...

Purple makes sense. Blue and red are the colors of light that are most effectively absorbed by chlorophyll-pigmented plant leaves. Yellow would be a lot less efficient because more would reflect off the green leaves.

Re: What are the mysterious light sources on light pollution maps?

#17

Post by inetknght »

yread wrote: post #12
amatecha wrote: post #8

Ah yeah, in the post's first "unknown light pollution" example, I figured it must be a greenhouse. I was driving through a relatively small town one time and was a bit freaked out by this ominous yellow glow off in the distance. Like, the whole sky was glowing [0]. I ended up driving out to try to find the source, and discovered it was a huge greenhouse/farm. Luckily not an extraterrestrial landing zone or so on ;) […

Yellow glow is understandable, but check out this purple one https://www.cbc.ca/news/canada/windsor/not-northern-lights-g...

I wonder how much money might be saved just by installing shutters to reflect the light (and heat) back into the greenhouse instead of letting it pollute everywhere.

Re: What are the mysterious light sources on light pollution maps?

#18

Post by uhnuhnuhn »

hermitcrab wrote: post #14

On https://www.lightpollutionmap.info/ there is a big pollution area in Russia, North of Khazakstan. There doesn't seem to be a city. Is this an oil field? One of the patches is at 67 degrees 42' N, 83 degree 47' E.

https://en.wikipedia.org/wiki/Vankor_Field

Re: What are the mysterious light sources on light pollution maps?

#19

Post by strbean »

yread wrote: post #12
amatecha wrote: post #8

Ah yeah, in the post's first "unknown light pollution" example, I figured it must be a greenhouse. I was driving through a relatively small town one time and was a bit freaked out by this ominous yellow glow off in the distance. Like, the whole sky was glowing [0]. I ended up driving out to try to find the source, and discovered it was a huge greenhouse/farm. Luckily not an extraterrestrial landing zone or so on ;) […

Yellow glow is understandable, but check out this purple one https://www.cbc.ca/news/canada/windsor/not-northern-lights-g...

> She said the municipality is trying to find the best way to address the issue, while still considering the economic side.

Just make them put tarps over the greenhouses!?

Re: What are the mysterious light sources on light pollution maps?

#20

Post by hermitcrab »

uhnuhnuhn wrote: post #18
hermitcrab wrote: post #14

On https://www.lightpollutionmap.info/ there is a big pollution area in Russia, North of Khazakstan. There doesn't seem to be a city. Is this an oil field? One of the patches is at 67 degrees 42' N, 83 degree 47' E.

https://en.wikipedia.org/wiki/Vankor_Field

Mystery solved. Thanks!
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