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Posted by defrost 1 day ago

LEDs’ potential to save our night skies(spectrum.ieee.org)
231 points | 173 commentspage 2
throwatdem12311 21 hours ago|
All the car headlights for new cars in Canada are LED and it makes driving at night painful and dangerous. So many times I’ve been nearby blinded by them and I can’t see anything ahead. And it actually physically causes me pain.
yonatan8070 19 hours ago||
But is that the fault of the LED? That sounds like the fault of whoever calibrated the LEDs' brightness and directionality.

If the beams were the right brightness and pointed downwards, we wouldn't be having this issue.

throwaway173738 15 hours ago|||
There will always be situations where you’ll be under the cut point of a low beam. If there’s a small incline then a flat intersection the drivers opposite the incline get the fill low beam. It’s part of what makes HID lighting dangerous to pedestrians. It obscures the vision of oncoming drivers turning left or right. Also if an automatic headlight system doesn’t react to turn the high beams off it will blind people.
GrinningFool 18 hours ago|||
Not really. When incandescent headlights are mis-aimed, it is generally not nearly as blinding or painful [for standard car headlights]. Mis-aims happen - it shouldn't be a risk to other drivers when they do.
bahmboo 14 hours ago||
I'm optimistic this won't be a problem in 10-20 years (I agree that's a long time). We have the technology in matrix headlights that were banned in the US and basically in Canada up until a few years ago. I expect to see kits on Amazon in a few years for retrofits. Since they need a camera and some brains they will likely start at many hundreds of dollars but that should come down.
mchusma 10 hours ago||
I am generally for a light government touch, but I think excessive light and sound are forms of pollution and should be generally regulated in a not-overly burdensome way (give people fix it tickets etc). Policing excessive light, and excessive blue light, would be pretty trivial. And I think cameras that automatically ticket loud vehicles would be amazing.
groos 12 hours ago||
I read through most of the article but didn't see motion sensors mentioned. A lot of suburban streetlights are lighting up empty streets at night. With a combination of motion sensing and LEDs, lighting could follow pedestrians. Cars really don't need street lights in most cases but even then, in higher risk areas, motion sensors could turn on streetlights just as long as needed.
wffurr 12 hours ago|
A motion sensor activated light unpredictably turning off and on on my street would be worse than the steady street lamps we have now. It would be even more distracting and annoying.
apparent 18 hours ago||
> The use of solid-state technology gives the lights an extraordinary life-span, often measured in decades rather than years.

I have found this not to be the case. They seem to last several years, but not an amazing period of time. Also, the ones that were installed in my home are quite expensive, something like $45 per can (the whole thing must be replaced), and the price to install is $30 per can because the company changed their plug design in the last 5 years. So I end up spending $75 for each light, which is roughly $10 per year per light (per light-year?). That doesn't strike me as a great value, especially because I can't change the lights myself due to the wiring/plug situation. Maybe that piece won't apply in future years, but it's still a lot even if it's just $45 for the darn can.

ssl-3 15 hours ago||
At home, my solution to that is to use lighting fixtures have Edison sockets inside for a bulb to screw into, just like they always used to.

The fixtures last forever, and may have already been there for half a century. It doesn't need changed.

The bulb lasts as long as it lasts, but is easily replaced. It can be dumb, or it can be smart. It can be changed for different color temperature or CRI or protocol or efficiency rating or whatever.

aidenn0 18 hours ago|||
Yes, I was wondering if they really last longer than sodium-vapor lamps, which last about 5 years at a 50% duty cycle.
apparent 18 hours ago||
I imagine they last longer than some other types, but it hasn't been an order-of-magnitude difference that was advertised. Also the cost/hassle is much more than expected.

We've put some smart LED bulbs into some fixtures, and those have been fine. But they've only been in for a few years, so we don't yet know their lifespan.

adrian_b 17 hours ago||
I have seen a lot of complaints about LED lamps with a short life, usually caused by defects in their integrated power supplies, typically arising from bad cooling.

On the other hand, I have more than a dozen LED lamps that have been continuously used for more than ten years and none of them has failed yet. They are mounted in classic Edison fixtures for incandescent lamps and they were made by Philips, but at the time when they were bought they were one of their better models, and having a 4000 K color temperature, i.e. very slightly yellowish, but not noticeably yellow, like the lamps with a color temperature less than 3000 K, which try to imitate incandescent lamps.

wkjagt 14 hours ago||
I am Dutch but live in Canada, and when I visit family in The Netherlands, I always notice how much darker it gets during the night, even when my family lives in a larger town than me.
chrisweekly 19 hours ago||
For those in the northeastern US, I highly recommend a visit to Mesawisla in Maine, it's a national dark sky park with cabins and an AMC lodge that provides fantastic food.
chrisweekly 13 hours ago|
argh, typo, too late to edit

Medawisla

https://www.outdoors.org/destinations/maine/medawisla-lodge/

theodorethomas 22 hours ago||
I wondered if a city-wide synchronised Pulse-Width-Modulation of LED lights could allow astrophotography (or even naked-eye astronomy) to be possible again, with a filter synchronised to the off-cycle.
Rotundo 22 hours ago||
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.
weberer 21 hours ago|||
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.
tredre3 18 hours ago|||
Surely a PWM of 10,000Hz wouldn't allow for night sky photography. With full exposure it can already take minutes of hours to take a night sky a photo.

And it's usually recognized that 1,000hz is the bare minimum to spare sensitive individuals from symptoms, with 2,500 usually used for safety margin. Then you have to account for some jitter in the synchronized network so you're looking at at best a 1/5,000 exposure.

Is that sufficient to be worth the trouble?

ireflect 8 hours ago||
You can still get a long exposure by accumulating many 1/5,000 exposure shots together. Just like a regular long exposure, this will still cancel out random noise and improve SNR, and also still has the tradeoff of motion blur. This kind of accumulation is commonly done in photography-adjacent technologies like spectroscopy.

Regardless, I agree with your larger point that the proposed system would be entirely impractical!

tzs 16 hours ago||||
> 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.

esikich 13 hours ago|||
That's unrectified LEDs flashing at mains frequency, not PWM.
coryrc 9 hours ago|||
No, because the phosphors glow for much longer than human persistence of vision.
fhdkweig 22 hours ago||
Los Angeles has the Griffith Observatory. To allow the city to have street lighting while not interfering with the observatory, the lights are sodium vapor lights that emit a specific wavelength that the observatory can filter out. Since LEDs also use specific wavelengths, this could have been done.

I was disappointed that the article didn't mention this, especially because they did mention sodium, but only as a pretty color.

OkayPhysicist 21 hours ago||
I quite like the 2 wavelength light that sodium lamps give out. When I was in school, my university gradually went from all sodium to all LED, and it was definitely a loss. The complete loss of hue, combined with the soft buzz of a dying sodium lamp had a certain otherworldly feel to it. I found it quite relaxing.
Sparkyte 18 hours ago||
The lights are not just impacting space but ecosystems switching to LEDs can save ecosystems too.
worik 17 hours ago||
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

ButlerianJihad 17 hours ago|
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!

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