Skyglow: Timelapse film dedicated to the need for light-pollution-free skies for stargazing


I don’t get it.

Even though it’s clearly post-production effects, this clip seems to say that light pollution doesn’t matter, because the skies over LA are glorious. Wouldn’t it make more sense to compare the LA sky to the Mojave desert sky?


We all love dark skies. That’s why those of us who live in the city like to get out from time to time and enjoy them.

Can’t really think of a reasonable way to mitigate the “growing threat” of light pollution without also making our cities dangerously dark. I disagree with the sentiment of their KS video that the “vast majority” of artificial light generated in our cities is pointed directly into the sky…

I’m sure they’ll make lots of pretty pictures though.

I agree… (with the article)
Lots of lights are very inefficient in directing their light.
When flying at night one of my “hobbies” is observing the different lighting used in communities.
If you can see a point of light from a plane, that light is shining directly into the sky. On the bright side :slight_smile: , over the past decade, I have been noticing more and more well-designed light fixtures – all you see is the pool of light on the ground (no point source - it’s like magic). I would think that the move to longer wavelength light (the pinkish stuff) might help a wee bit as well.

Edit to clarify “agreement”

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I am sincerely glad you asked. There are a number of things that we can do.

1 - Eliminate upward light. This is as simple as exchanging heads on existing light poles for something that uses a clear, flat lens and lamp higher up in the housing to prevent spill light from going up into the sky. This obviously costs money and many areas are reluctant to spend the money on this infrastructure when bridges need work. But we can’t use these anymore:

As you can see they do point a lot of light outward and upward.

(Photo Credit: Unshielded Light Waste, from Light Pollution: The Dark Side of Outdoor Lights)

Even straight out is basically lighting up into the sky, so the math about the vast majority pointing into the sky is absolutely right on. We need to start using these:

2 - Use less light in the first place. This is a tough one to get past city councils and the like, especially in urban areas, but we need to trim down the amount of lumens we make. One footcandle is the average on a New York street and sidewalk, I see much more in other towns where it’s simply not needed.

3 - Use smarter controls. Streetlights burn all night long, even at 3 AM when there’s nobody out there. A much more efficient use of light would be a dimmed setting that lowers intensities that is connected to a series of motion sensors to then ramp up to full intensity when people or cars approach. Japan already does this in public building hallways and it saves them millions in Yen each year in energy costs to only have the lights come on when the are needed.

We don’t need to jump back down to torches and flashlights for everyone, we just need to be smarter and more selective on how we use our light. Flagstaff and Tucson are great examples of communities who work with their local observatories to limit their light use while maintaining safety. Using light selectively and wisely is the key here, not just making it dark.

Nobody is also advocating that this is the correct response everywhere. New York actually has code that requires brightly lit signage in the Times Square area. This environment has always been regarded as a brightly lit urban environment and is designed to maintain that style for the foreseeable future. But there are locations that we can and should be reducing the amount of sky glow.

Feel free to post any more questions, I’ll be glad to answer.

[May 4, 2015 – Edited by Rob B. to include photo credit and link, at the copyright proprietor’s request.]


Is it true that the dark is dangerous?


Well, if it’s pitch black you are likely to be eaten by a grue. Does that count?


Yeah, that’s a good point. No one wants to come to a gruesome end.

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Lanterns are key.

I’ve actually been lucky so far without benefit of artificial light sources. My night vision works pretty well as long as I don’t spear myself in the retinas with a car headlight or a neighbor’s flood lamp. I walk often, frequently at night, sometimes several nights a week, ranging over an area of several square miles (not all at once!). I live on a street with buried cables, i.e., no phone poles and no street lights, and the neighborhood is forested and only partially built out, with lots of dark spots on the map. Leaving the neighborhood, I can move along an unlit highway and be in farmland before long, with interesting possibilities there. It’s glorious. It wouldn’t be the same at all if it were lit.

For a long while the main road outside my neighborhood was mostly-closed for renovation, and I could turn off the lights in the house, step down into my unlit garage, walk outside to my unlit driveway, next to the similarly-unlit driveway of my neighbor, walk down my unlit street and out into the unlit wider world, then return one to four hours later after walking in the dark the whole time. Incredible.

Since you’re up on matters of public lighting and want to keep the light where it’s wanted, I thought you might appreciate the rare opportunity that comes from living on an unlit street.


The pitch of that video is a little disingenuous, because there’s no question of ever seeing a sky like that in a city. Or at least, not a city you’d ever want to live in (since it’d have to shut down at sunset). The real problem is that you can’t see the stars 50 miles outside of a city like LA, and of course the people affected by that don’t have much political sway over city governments.

There’s a strong case for good lighting in cities, but for city dwellers, it’s nothing to do with dark skies. It’s just that urban environments can be so much more attractive than the flat orange dystopias we’ve come to accept. If you think about it, it’s kind of baffling that city governments will spend money on trees and benches and trash collection to make streets pleasant, and then light them like a Russian mafia interrogation warehouse. With cities everywhere modernising their street lighting, it’s a great opportunity to bring this up.


No. I’d totally let my kids play on a dark LA Freeway. But the growing threat of sky glow, on the other hand…
Just kidding. I don’t have kids.

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From what I have seen it looks like lighting set up to reduce sky glow is also lighting set up to reduce glare, and is therefore both more effective and more pleasant to look at.

A lot of the fixtures that leak upward also leave the bulb directly visible which his your night vision. They also create very bright spots from the light hitting surfaces right near the bulb.

When light pollution is minimized there are not nearly as many very bright areas and very dark shadows.


Oh, I certainly do, and it just proves the point that we don’t need as much light as people put out there. Having navigated through the Maine woods via starlight I’m a big fan in letting your eye do the work it’s designed for.


Older people with lower-sensitivity eyeballs would perhaps disagree.

I’m familiar with macular degeneration. And I maintain that we don’t need as much light as people put out there.

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