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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?

#71

Post by leoh »

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 ;) […

Same thing happened to me -- some greenhouses off highway one near Half Moon Bay

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

#72

Post by dylan604 »

caymanjim wrote: post #42
donkeyd wrote: post #10

Earlier quoted context omitted.

Only 90 minutes? For me it's at least 3 hours to get to Class 4 on the Bortle scale. Class 2 is probably more than 5 hours. Only alternative is the sea. I'm planning to take a trip to a Class 1 this summer, it'll be hard to find a place that dark that is reasonably reachable though.

Go to an island and hope the power goes out. I was on Cayman Brac (a tiny Caribbean island) during a power outage, and even though there was a full moon, the view was amazing. Then there was a lunar eclipse that I hadn't even known about in advance. Most amazing sky I've ever seen.

Islands tend to be pretty close to water/ocean. The moisture in the air has always played havoc with my attempts at imaging from these locations. My bucket list destination is Atacama.

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

#73

Post by Wald76 »

duderific wrote: post #64
tzs wrote: post #60

The map of the United States raises an interesting question. There is a pretty distinct line down the middle, with nearly opposite light/dark patterns on different sides of the line. To the east, it is mostly bright areas with islands of dark. To the west, it is mostly dark areas with islands of bright. If you look at a regular map, nothing really stands out to explain the difference. It is not like there is, say, a…

My guess would be that the land is not as conducive to farming west of that line, both in terms of soil and weather. So early settlements didn't occur there, and thus cities did not emerge from those areas. The cities that did evolve in the West were based on different resources: ports around the ocean, mining, oil, railroad stops etc.

That’s correct, the US population density correlates fairly closely with the average annual rainfall: https://en.wikipedia.org/wiki/United_States_rainfall_climato...

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

#74

Post by 205guy »

tzs wrote: post #60

The map of the United States raises an interesting question. There is a pretty distinct line down the middle, with nearly opposite light/dark patterns on different sides of the line. To the east, it is mostly bright areas with islands of dark. To the west, it is mostly dark areas with islands of bright. If you look at a regular map, nothing really stands out to explain the difference. It is not like there is, say, a…

I believe it's the beginning of the Great Plains and generally lacks water. It's not dry like a desert, but compared to the temperate forests and rivers of the East, South, and Mid-West, it is. It is intensively farmed now, using pumped aquifer water (https://en.wikipedia.org/wiki/Ogallala_Aquifer), but it never developed the population density of the East. Geology maps also show this divide, so it is based on the underlying rocks, as well as weather patterns from the Rocky Mountains I suppose.

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

#75

Post by dylan604 »

BurningFrog wrote: post #61
tzs wrote: post #60

The map of the United States raises an interesting question. There is a pretty distinct line down the middle, with nearly opposite light/dark patterns on different sides of the line. To the east, it is mostly bright areas with islands of dark. To the west, it is mostly dark areas with islands of bright. If you look at a regular map, nothing really stands out to explain the difference. It is not like there is, say, a…

Yeah, there is a pretty distinct line from Winnipeg to San Antonio, separating light from dark. If you look at a population density map, it looks quite similar: http://dafi1637.blogspot.com/2017/10/united-states-populatio... I think that explains the immediate effect. You can of course then wonder why the population is distributed that way, but I feel I've done enough here :)

>Yeah, there is a pretty distinct line from Winnipeg to San Antonio, separating light from dark.

That's the I-35 corridor. An interstate highway running north/south all the way from Mexico to Canada. It was probably the most hyped/utilized part of NAFTA. I live in Dallas where I-35 runs through (actually splits in Waco to cover both Dallas and Ft. Worth, reconnecting north around Denton). I grew up in a small city south of Dallas, and remember all of the highway construction that got spurred by NAFTA. That area (Ellis county) also had a construction boon due to the Super Conduction Super Collider.

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

#76

Post by solstice »

nine_k wrote: post #69
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 ;) […

I wonder why don't they use mirrors to reflect the light back at night time. Metallized PETF film is strong enough, very lightweight, and not expensive, while reflecting, say, 95% of the light. Could save them a lot in electric bills.

Maybe it's to do with having to peel it back during the day? Should be quite an increase of mechanical complexity compared to just switching the lights on and off

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

#77

Post by paulmd »

vvanders wrote: post #62
kabacha wrote: post #58

Earlier quoted context omitted.

They are absolutely awful. I've lived relatively close to one and hadn't seen night's sky for the whole duration I stayed there. Actually the whole town's sky was filled with light polution from one cucumber farm.

They also tend to generate a ton of RF noise if not properly filtered.

I was having problems with my cable internet periodically dropping out for a few minutes at a time, it took them two or three tries, and every time the support guy came out they were very careful to tell me that "your neighbors grow lights may cause that when they switch on at some particular time every night". So I guess they do put out quite a bit of RF noise ;)

("of course, it's company policy never to imply ownership in the event of a dildo.")

Think it was a firmware bug in the modem, because the modem never realized it was offline or showed a connectivity disruption on the street. Luckily it dropped off one time while I was on the phone with a tech. They were using a new Charter Spectrum branded modem and as soon as they swapped to an Arris it stopped happening.

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

#78

Post by dylan604 »

TallGuyShort wrote: post #37

A lot of fracking sites near me have exceptionally bright lights at night when they're being actively worked on. I suspect the brightness shown might be regular old electric lights, not just gas flares.

Car parks are notorious light polluters as well. These are large parking lots where car manufacturers off load cars by rail for their "last mile" delivery to the area dealerships. The lights are meant to keep the thief away. On top of the horrendous light pollution, they also cause massive* traffic headaches where the trains can come to a complete park for 20-30 minutes while the train cars with autos are connected/disconnected.

*The one I lived near was in a pretty small town, so the traffic might have been only 10-15 cars on either side of the tracks. Massive is directly proportional to your direct involvement of being stuck.

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

#79

Post by salgernon »

mattkrause wrote: post #24
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…

Prudhoe Bay at the top of Alaska must be something like that, because it's bigger than many major cities.

I was looking around in that area (on the maps) and apparently its an oil field kind of thing. Reading up on it, there's restrictions on being able to actually access the ocean from that location - concerns about security, I guess.

I thought an interesting nearby spot (east of Prudhoe Bay) was Cape Parry Bird Sanctuary. On the west side there was a military base that had since been decommissioned and what looks like an abandoned airstrip. But it still is bright for that area.

Apple Maps shows more detail for that location; maps.google.com didn't have very high resolution imagry.

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

#80

Post by loeg »

donkeyd wrote: post #10
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.

Only 90 minutes? For me it's at least 3 hours to get to Class 4 on the Bortle scale. Class 2 is probably more than 5 hours. Only alternative is the sea. I'm planning to take a trip to a Class 1 this summer, it'll be hard to find a place that dark that is reasonably reachable though.

Darksitefinder scores a good portion of the remote North Cascades in Washington a 2 on a 1-15 point scale, which is ~4.5 hours from Seattle during winter (with highway 20 closed).
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