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Simple streetlight hack could protect astronomy from urban light pollution

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Re: Simple streetlight hack could protect astronomy from urban light pollution

#51

Post by mannykannot »

One downside of this mechanism is that it reduces the light-gathering power of the telescope according to what fraction of the cycle the shutter is open.

Another possible concern may be that while the shutter is partially open, the resolving power of the telescope may be reduced, introducing diffraction artifacts into the image. A liquid crystal or Kerr cell shutter opens and closes everywhere across the full aperture at the same time, but they introduce polarizing elements into the light path.

The shutter in StealthTransit's current product is a leaf shutter, and for its original purpose of blocking satellite interference, the above concerns are probably not an issue, if the shutter is open almost all the time.

https://stealthtransit.com/

Re: Simple streetlight hack could protect astronomy from urban light pollution

#52

Post by canoebuilder »

qmarchi wrote: post #41
canoebuilder wrote: post #31

Earlier quoted context omitted.

> Cheaper to operate I’ve seen in a number of places where the led lights have rapidly degraded, putting out really unpleasant bluish, purplish hues, as if the super bright daytime like sports field lighting everywhere wasn’t already bad enough. So this rapid degradation necessitating replacement no doubt eats into some of the cost savings. Also, “cheaper to operate” mostly seems to have turned into “pump out more ph…

There was some historical reporting where lights were delaminating because of a bad batch of panels produced by Acuity. It's not representative of the majority of LED installations, but each install may vary. https://fee.org/articles/why-are-some-us-street-lights-turni...

Interesting thanks. It may not be representative of a majority but it seems pretty widespread, and it is representative of a type of problem led lights are prone to, at least right now.

I’ve had issues with household LEDs that needed replacing well before expected lifespan.

I also saw this article some time back discussing issues with LEDs. https://nymag.com/strategist/article/led-light-bulbs-investi...

I’m not against LEDs, but the usage and implementation in a lot of cases to date could be better.

Re: Simple streetlight hack could protect astronomy from urban light pollution

#53

Post by jcalvinowens »

quietpain wrote: post #36
bradley13 wrote: post #5

Right. They're going to get all the streetlights in an entire city to blink in unison. Sure they are. Anyway, in most cases the LEDs don't run at 100%. In our area a, I happen to know that they are between 29% and 40%. That dimming is accomplished by blinking. Which would conflict with the idea of having them blink synchronously. Much simpler solution: ensure the LEDs ghts are directed exclusively downward, and have…

In Europe the entire mains grid is synchronised - the smallest deviation in fase & frequency is the same. It’s fairly straightforward to sync them with this distributed reference clock. Edit: https://www.mainsfrequency.com/

The frequency observed across all loads in the system might be very consistent, but the phase is absolutely not. Different types of transformers introduce different phase shifts, so this can't work.

Re: Simple streetlight hack could protect astronomy from urban light pollution

#54

Post by cassianoleal »

Anotheroneagain wrote: post #45
cassianoleal wrote: post #38

Earlier quoted context omitted.

> You could see the attackers just as well as they see you. That's only if they're moving within the sensors that switch on the light. > The problem with warm lights is that they are much harder to see in the dark. Not sure what "in the dark" means here. Light by definition is easier to see in the dark than it is in light as it has less light to compete with. In any case, I find warm lights much easier. Cold lights a…

I mean they need to be pretty bright to be visible at all. Notice how red leds still look dim at night, but green blue are shining in the dark room. The eye can't adapt well to dim warm light. And that is the other reason. Those would still make nights look like nights, they should look sort of moonlight like with reasonable brightness.

I'm still unsure what you're advocating for.

Dim, but cool coloured lights? That's certainly better than bright cool ones but I still find them very annoying and overstimulating at night.

The only thing I can't do with dim, warm lighting is read small text from something other than a backlit screen. For everything else, it's perfectly fine. And if I do see myself having to do that, I'll just add a spot of light to what I'm trying to read, problem solved.

Re: Simple streetlight hack could protect astronomy from urban light pollution

#55

Post by sokoloff »

Marsymars wrote: post #13
nightowl_games wrote: post #8

Earlier quoted context omitted.

> Even better: turn the darned things off when they are not needed - why illuminate empty streets? That is a way better idea than the one in the article, for sure. So many benefits. Would need the motion sensing technology to be top notch tho. Need to illuminate for pedestrians as well. Or perhaps illuminated sidewalks, or smaller lights for pedestrians.

Some of the newer street lamps in my area have smaller light for pedestrians! They're mounted at human height and shine down on the sidewalk. Motion sensing, I find, similar to LED technology, is often used more for increasing lighting levels rather than decreasing. My pet peeve are people who have motion sensors that activate their 20k lumen floodlights based on motion on the public sidewalk. Cities should not allow…

> Motion sensing is often used more for increasing lighting levels rather than decreasing

Isn't that just a matter of perspective [whether the presence of motion is used to increase lighting or the absence of it is used to decrease]?

Re: Simple streetlight hack could protect astronomy from urban light pollution

#57

Post by johnea »

I wonder what the PWM frequency is for teh "flickering"?

I'm constantly distracted by light flickering in my peripheral vision. Computer monitors, traffic lights, car head and tail lights. Many modern LED lights are already flickering. It's often impercetible in my focused vision, but in peripheral vision is clearly visible.

I think it should be in the KHz at least...

Re: Simple streetlight hack could protect astronomy from urban light pollution

#58

Post by globular-toast »

bradley13 wrote: post #5

Right. They're going to get all the streetlights in an entire city to blink in unison. Sure they are. Anyway, in most cases the LEDs don't run at 100%. In our area a, I happen to know that they are between 29% and 40%. That dimming is accomplished by blinking. Which would conflict with the idea of having them blink synchronously. Much simpler solution: ensure the LEDs ghts are directed exclusively downward, and have…

Dimming is usually done by pulse width modulation. So you can definitely get them to blink at the same frequency, you just change the pulse width.

Re: Simple streetlight hack could protect astronomy from urban light pollution

#59

Post by probably_wrong »

todfox wrote: post #56

This doesn't help people like me who just want to stargaze. How about, empty city streets don't need to be lit up at 2 am. And what lighting there is, is too bright, too intrusive, and overused.

As a man I'm all for it. But I think the women I know would object to walking at night on pitch-black streets.

Re: Simple streetlight hack could protect astronomy from urban light pollution

#60

Post by amluto »

No.

The article is light on details, but:

> A simple device that makes LED lights flicker at a very high frequency that is imperceptible to the human eye

> shutter, which needs to be lightweight and agile enough to blink about 150 times per second.

Subjecting an entire city to 150 Hz flicker is not even remotely acceptable. IMO this needs to comply with IEEE 1789.

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