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LEDs’ potential to save our night skies

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Re: LEDs’ potential to save our night skies

#131

Post by stouset »

wongarsu wrote: post #28
trollbridge wrote: post #19

Earlier quoted context omitted.

Wouldn't it be more reasonable to just expect people who want to walk places in the dead of night to wear a headlamp? They're cheap, easy to recharge, and can be adjusted for various brightness levels.

People associate a lack of lighting with crime I vaguely remember that studies showed that lack of streetlights does not create crime, but the crime that happens anyways prefers badly lit areas. But from a pedestrian's perspective that's not much relief, you'd still avoid those areas. Which is not what a city planner has in mind for a park

Also part of the issue is that lighting at night creates enormous contrast between dark areas. Even darkness is something our eyes are well-adapted to, and we can see surprisingly well with even a little moonlight. We struggle with alternating bright/dark areas.

Re: LEDs’ potential to save our night skies

#132

Post by ButlerianJihad »

Since I picked up a Pixel phone, I've been doing some amateur astrophotgraphy, and mostly from the balcony at my apartment.

However, I live in a built-up urban area, and my home is absurdly light-polluted. Like, you wouldn't believe it! The parking lot here is ringed with flood lamps that are aimed into our windows. So every hundred feet or so, there is a bright-as-the-Sun lamp in my face, and with a clear view, I can spot about five of them.

So from my balcony, my only hope to get some darkness for the camera is to get into shadows. The railings provide a band of shadows that I can use to block the floods from getting on my lens. So if I position the camera juuust right, it kinda feels darker than it is, and I've got to say I've captured some impressive starfields, down to magnitude 9 or dimmer, including bodies such as Uranus and 4 Vesta.

I also found that the ballcourts in the rear of my property provide this unique "cave" situation with lots of shadows where I can capture the sky directly overhead, and to the west. This is how I photographed the last lunar eclipse.

Now that's my view to the west and 225° (due southwest). If I go on the other side of the property to look east, I've got the same crazy situation with flood lamps, but there's basically no way to hide in shadows. I literally cannot photograph anything rising in the east if it is dimmer than the Moon.

So really, my astronomy hobby mostly consists of doing some great editing, curation, identification, and mostly simulation from the comfort of the air-conditioned indoors. I enjoy what sightings I can while outdoors, and that's included some meteors, the ISS, Tiangong, and a few Vandenberg launches. We're still hanging in there!

Re: LEDs’ potential to save our night skies

#133

Post by worik »

We have been working hard on this in New Zealand, in the South Island

We started in Tekapo (https://www.darkskyproject.co.nz/) which being rural with a very low population density, and mountainous and with existing observatories to protect

In recent years the effort has moved into the cities (https://www.dunedin.govt.nz/council/policies,-plans-and-stra...)

Interestingly people who live on hills, overlooking the suburbs, complain the lovely view of the sparkling streets was going dark!

But not only does it preserve the stars it is much cheaper, so not going back

Point is: this can be done and the nighttime rewards and financial rewards make it worthwhile

Re: LEDs’ potential to save our night skies

#134

Post by teamonkey »

amiga386 wrote: post #98
adrianN wrote: post #41

Earlier quoted context omitted.

TFA claims that lights don’t reduce crime, but I‘d like to see the exact meaning of that statistic (eg dark places are less frequented hence less crime?).

TFA doesn't even claim that. TFA links to an advocacy website trying to convince authorities to put out less light pollution. It claims improved lighting (presumably brighter) doesn't reduce crime, and it claims a reduction (but not elimination) of lighting doesn't increase crime. I would say that going from no lighting at all, to some lighting, on urban paths, improves safety (not tripping over unexpected obstacles)…

Nobody is trying to remove all street lighting. There are plenty of practical suggestions on here and in that document about how things can be improved without reducing safety.

Re: LEDs’ potential to save our night skies

#135

Post by fch42 »

Loic wrote: post #58
fhdkweig wrote: post #12

Earlier quoted context omitted.

Those things drive me nuts. There is a walking path that I frequent, and I can't use it at night because they are spaced every 20-30 feet. When I am not under them, they are off and my eyes adjust to the darkness and as I pass under one it flips to full daytime brightness and blinds me. As soon as I walk away from it, everything goes dark again, but my eyes had adjusted to the daytime brightness of the lamps. And I k…

The timing and brightness is well adjusted, it feels natural, like a friendly ghost taking care of you.

unfortunately they never are. Brightness-adjusted, that is. Everyone installing lighting fixtures these days believes they must be daylight-level bright. The only ghosts you see are afterimages if you happen to look straight at the streetlamp ...

(I find it odd; dark-adapted eyes see a lot, including movement in shadows or low-contrast obstacles - after all, our bodies know how to see well at moonlight levels of illumination. Why are we so keen to kill this ability?)

Re: LEDs’ potential to save our night skies

#136

Post by tzs »

weberer wrote: post #40
Rotundo wrote: post #23

Earlier quoted context omitted.

Using PWM to dim lights should be banned wholesale. Many people, me included, get crazy headaches from the worst lights and mild discomfort from the best ones. It's also completely unnecessary as non-flickering bulbs do exist and are readily available for the same price.

Those are probably 50-60 hz flickering from the mains frequency rather than PWM. (Or 100-120 hz due to the rectifier). Actual PWM ICs drive LEDs over 10,000 hz, which is truly imperceptible to the human eye.

> Actual PWM ICs drive LEDs over 10,000 hz, which is truly imperceptible to the human eye.

But then you can get capacitors or inductors emitting a very annoying 10 kHz whine. There are higher end LEDs for various commercial uses that use PWM at over 20 kHz to avoid that.

Re: LEDs’ potential to save our night skies

#137

Post by chasil »

adrianN wrote: post #39
uv-depression wrote: post #25

Greenhouses here in the lower mainland of British Columbia have been devastating to the night sky. It's quite depressing how little society values the night sky, something that's been an important part of every human culture for longer than recorded history. I've taken friends out to thoroughly mediocre skies (Bortle 4-5) and they've been very impressed, because they're used to city lights (Bortle 9) where you can ma…

Putting astronomy on the dark side of the moon would probably work better than putting it into space because you can use some local material for construction.

I have read elsewhere that spinning mercury would be used as the mirror.

Re: LEDs’ potential to save our night skies

#138

Post by shagie »

chasil wrote: post #137
adrianN wrote: post #39

Earlier quoted context omitted.

Putting astronomy on the dark side of the moon would probably work better than putting it into space because you can use some local material for construction.

I have read elsewhere that spinning mercury would be used as the mirror.

The suggestions that I've seen for astronomy on the far side of the Moon have largely been about radio astronomy rather than optical. The lack of the ionosphere which otherwise blocks and distorts 10 meter and longer radio and using the Moon itself as a shield from the radio noise of Earth makes it more interesting.

Radio telescopes only need a wire mesh to deploy (rather than polished optical mirrors). https://www.skyatnightmagazine.com/space-science/arecibo-tel... has a view under Arecibo.

https://www.nasa.gov/general/lunar-crater-radio-telescope-lc...

---

The liquid metal mirror telescopes https://en.wikipedia.org/wiki/Liquid-mirror_telescope are interesting in part because you can get liquid mercury temperatures near room temperature on Earth.

It's theoretically possible for the moon - https://ui.adsabs.harvard.edu/abs/2007Natur.447..979B/abstra...

    A previously proposed liquid mirror telescope, based upon a spinning liquid metallic alloy, is not appropriate for infrared applications, which will require a liquid below 130K. Here we report the successful coating of an ionic liquid with silver. The surface is smooth and the silver coating is stable on a timescale of months. The underlying ionic liquid does not evaporate in a vacuum and remains liquid down to a temperature of 175K Given that there are ~10^6 simple and ~10^18 ternary ionic liquids, it should be possible to synthesize liquids with even lower melting temperatures.
... But this seems a bit more speculative. It wouldn't be mercury and requires a yet to be discovered liquid metal that is stable for months at 175 °K.

Re: LEDs’ potential to save our night skies

#139

Post by computably »

qurren wrote: post #105
uv-depression wrote: post #102

Earlier quoted context omitted.

(1) Considering there are now multiple companies planning to launch their own fleets of tens of thousands, satellites need replacing, etc, even if this was completely accurate, this will be a continuous and ongoing issue as it has been for years. (2) The standards for astrophotography and for professional astronomical measurements are somewhat different! Also, I think you meant median stacking; mean stacking doesn't…

Some good points. However: > replacing the majority of air travel with high speed rail I absolutely LOVE high speed rail, but I will note that it is correlated with far more light pollution than air traffic. I say correlated because typically high speed rail is routed through high-density population centers, but if there aren't population centers, you'll have to have plans to create them in order to support the rail…

That's a backwards argument. Flights in California between SF and LA will obviously travel a continuous line across California. Yes, the populated areas have light pollution, but that's because they're, y'know, populated areas. HSR itself would add nearly no light pollution outside of the existing population centers, in contrast to flights.

Re: LEDs’ potential to save our night skies

#140

Post by parl_match »

garbagewoman wrote: post #130
qurren wrote: post #99

Earlier quoted context omitted.

Starlink gets a lot of flax for it but as an avid night sky photographer myself (IG: @dheeranet) who regularly goes to Bortle 1 parts of the world, I haven't found them to be an issue at all. 1. They are only visible when they are spinning up to orbit 2. They are too dim to desensitize your eyes, and are extremely easy to remove with the most basic of outlier rejection techniques; netizens often amplifiy outliers by…

Both are real issues, to be clear. LEO satellites are a real and increasing issue.

Yes, but one is a vastly smaller issue than the status quo issues.

Starlink gets a lot of attention because it's new, and because it's run by a polarizing guy who sucks.

Meanwhile, the airplane and streetlight situation has been destroying night sky photography for decades, to the point where photographers consult charts and have communities tracking the best times of years to minimize the hours of driving you have to do.

But let's "both are real issues" it, sure.

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