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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?

#41

Post by Zenst »

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 ;) […

It does make you wonder if it's not just moths attracted to strange lights at night.

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

#42

Post by caymanjim »

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.

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.

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

#44

Post by teilo »

robbrown451 wrote: post #43

You'd think they'd do better at containing the light from the grow houses, so more ends up on the plants and less making it to space. Like, foil or something?

I mean, people who grow pot figure out how to hid the light, so yeah.

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

#45

Post by ceejayoz »

jschwartzi wrote: post #39
paulie_a wrote: post #32

Earlier quoted context omitted.

Did Chicago figure out the issue with LEDs and snow. The old lights melted snow, the LED lights did not

Chicago plows.

Snow on the lights, not the roads.

I discovered LED headlights on cars don’t melt off the ice like incandescent do the last time I drove in an ice storm.

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

#46

Post by ct520 »

teilo wrote: post #44
robbrown451 wrote: post #43

You'd think they'd do better at containing the light from the grow houses, so more ends up on the plants and less making it to space. Like, foil or something?

I mean, people who grow pot figure out how to hid the light, so yeah.

or do they.. Did you see all the light up in northern cali? LOL

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

#47

Post by _jal »

GekkePrutser wrote: post #31
bzbz wrote: post #23

Earlier quoted context omitted.

Take them off during the daytime. They're not permanent installments.

Those greenhouses are the size of many football fields.. Putting tarps over them is a job that will take many days :) But yeah shutters or something smarter (like two-state glass) should work IMO. I think you even get glass that can switch to mirror mode.

> like two-state glass

That would be crazy-expensive. A lot of greenhouses use poly-film, to give you an idea of the budget. Replacement cost is a large factor.

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

#50

Post by crazygringo »

robbrown451 wrote: post #43

You'd think they'd do better at containing the light from the grow houses, so more ends up on the plants and less making it to space. Like, foil or something?

Since these are greenhouses they have to be clear to let the light in during the day, I assume.

Anything that's going to reflect light to prevent it from leaving at night will also block the sun from hitting the leaves during the day, unless it's a complicated mechanical system that can be folded up during the daytime.

I'm guessing such a reliable mechnical system together with maintenance is much more expensive than the light leakage.

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