[HN Gopher] Simple streetlight hack could protect astronomy from... ___________________________________________________________________ Simple streetlight hack could protect astronomy from urban light pollution Author : bookofjoe Score : 35 points Date : 2023-11-18 15:06 UTC (7 hours ago) (HTM) web link (www.space.com) (TXT) w3m dump (www.space.com) | petee wrote: | In my area I've noticed the problem isn't so much that they are | brighter, but that our new bulbs just emit light near 180 degrees | (sideways) with no control over direction. | | It causes light to flood into homes, and more than half isn't | even illuminating the road. They also have no diffusion, so its | harsh on the eyes. A bad design all around | toss1 wrote: | Requiring them to change the directionality of the light, e.g., | ensuring that 100% of it is directed downward at the illumination | target, instead of just splashing it everywhere, would be far | better. | | This 150 Hz flicker may be above the flicker fusion threshold [0] | for humans, but not for many animals. Excess lighting hours | already massively screw up everything from sleep cycles, feeding | patterns, growth patterns migration patterns, etc. in insects, | birds, mammals, and plants, and contribute to the human caused | mass extinction. Making it flicker would only exacerbate it. | Perhaps if the flicker was at a rate in the kHz region, it | wouldn't add to the interference. | | But the best idea is to either ban lights altogether, or put them | all on motion sensors, so both public and private lighting is | turned-on only when needed. | | [0] https://en.wikipedia.org/wiki/Flicker_fusion_threshold | canoebuilder wrote: | Very excited to see the headline, but the "hack" was highly | underwhelming, disappointing, disconcerting. | | We need to be reducing light pollution for the benefit of humans | and other life forms, not just telescope machines. | | The solution is less light, and more targeted, well thought out, | aesthetically pleasing use of it. Warmer color temperature, | shining it just where and when needed and reevaluating just how | much illumination is wise and called for at night. | bradley13 wrote: | 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 only as much illumination as | needed. | | Even better: turn the darned things off when they are not needed | - why illuminate empty streets? | nightowl_games wrote: | > 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. | Marsymars wrote: | 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 those. | sokoloff wrote: | > 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]? | ikekkdcjkfke wrote: | I it find harder to see objects under street lights than a | person with a head lamp or a car, everything just blends into | one color | Anotheroneagain wrote: | No it's a horrible idea, imagine the lights turning on and | off as people pass. No! | cassianoleal wrote: | Indeed that would be terrible, especially in dodgier areas. | Not only you're advertising your position to potential | attackers, but you're also less likely to see them until | they're very close. | | I believe relatively dim, warm coloured lights are a much | better idea. | canoebuilder wrote: | Last sentence is a fine idea, it is also possible to move | toward developing a society where "potential attackers" | is a thought much more distant in people's minds. | cassianoleal wrote: | > it is also possible to move toward developing a society | where "potential attackers" is a thought much more | distant in people's minds | | Amen, but alas we're not there. | | In any case, threats don't always come from purposeful | attackers. It's useful to see animals, vehicles and bikes | with no light, etc. | canoebuilder wrote: | > _Amen, but alas we're not there_ | | What is troublesome is that many places, that many of us | probably hail from, "were there" not so long ago, and it | was destroyed by duplicitous, malicious political and | cultural actors. | | Having "safe streets" is not a pipe dream. Indeed not | having them is a symptom of people trying to destroy our | societies. | Anotheroneagain wrote: | You could see the attackers just as well as they see you. | I meant because of the annoyance that it would create. | | The problem with warm lights is that they are much harder | to see in the dark. Maybe dim lights around 505nm would | be a better idea. | cassianoleal wrote: | > 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 | are too much sensorial information for me. In any case, | street light at night shouldn't be meant to allow you to | see everything like it's a sunny day. It's supposed to | give you enough light that you can see your surroundings | and potential threats around you. For that, warm lights | should be more than enough. If you need more light | clarity, light your own phone torch or something. | canoebuilder wrote: | > _If you need more light clarity, light your own phone | torch or something._ | | Good point! In this case of nighttime lighting | infrastructure it has become so vastly overbuilt as if to | save people "the trouble" of these simple targeted | solutions. | Anotheroneagain wrote: | 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. | cassianoleal wrote: | 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. | eszed wrote: | Thinking like an attacker: find an ambush spot - probably | near the trigger-point of the motion-sensor; hold very | still; light goes off; victim approaches; ???; profit. | | I agree with you, though: lights blinking off and on all | the time are not great. I drove somewhere in Europe where | they did that with streetlights on major roads, and found | it startling, long past the point at which I'd have | assumed I'd become used to it. It wasn't the ones that | were responding to me, it was the ones that responded to | traffic on the opposite side of the road - they'd _flash_ | on in my peripheral vision and make me jump. Did not | like. | galdosdi wrote: | I'm not sure I'd be so quick to dismiss the feasability, at | least not based on your reasoning so far. | | FM Radio stations have managed to accomplish getting the | speaker in your car radio to "blink synchronously" according to | a complex signal pattern in the exact same way as millions of | other radios simultaneously.... for about a century now. As | long as all streetlights are in locations with good radio | reception (which, since they're all on streets and are tall, is | likely), it would not be that hard to implement in principle a | central FM or other radio signal that oscillates according to | the expected blinking. Lights that are engaging in dimming | could multiply another signal by the central signal to diminish | it even more. | coryrc wrote: | You must not be familiar with multipath interference. Radio | isn't quite as synchronous as you believe it to be. | saltcured wrote: | And of course the light itself is also undergoing multipath | distortions like the radio signal. And for astronomy, the | changing atmosphere might be the most important secondary | reflection. And the multipath arrangement between emitter | and observer is different for each pair. | | Could you make a dark period long enough to mask the | multipath variance among emitters and observers? Or would | this dark period be so long as to cause annoying flicker? | Evidlo wrote: | Wavelength of FM radio is about 3m, so you only have to be a | few centimeters shifted to be seeing an entirely different | phase and be out of sync. | da768 wrote: | Why not, just sync them to the AC power grid they're all | powered from. | jcalvinowens wrote: | Different types of transformers introduce different phase | shifts. | dahart wrote: | Yes exactly, aim them downward and turn the unused ones off, | which is most of them most of the time, and the problem will be | solved for everyone. The reason we should do it is that it will | save money and power for everyone, the night sky is just icing | on the cake. | | Getting lights to blink in unison is a neat idea, and | technically not hard nor too expensive for _new_ lighting. | Personally I think the biggest problem with it is that cities | aren't going to agree to overhaul all existing outdoor lighting | only for the sake of people using telescopes. Even if there was | widespread buy-in this is a project that could easy take 50 | years or more, and cities might be reluctant to commit to this | idea right when technology is rapidly changing. | klyrs wrote: | > They're going to get all the streetlights in an entire city | to blink in unison. Sure they are. | | Thre are a super simple and effective distributed algorithms | for this, if each lamp can see another few lamps. They don't | even need a good clock, just a relatively stable oscillator | within a few percent of a standard frequency, a light sensor | and an integrator. | | I agree that it's better to just put hoods on the lamps to | direct the light to only where it's needed, but distributed | synchronization is a solved problem. | quietpain wrote: | 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/ | jcalvinowens wrote: | 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. | globular-toast wrote: | 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. | gmiller123456 wrote: | Article has a lot of fluff and ads. Tldr; synchronize flipping | the street light on and off, and opening and closing a shutter in | the telescope. | | So only works for astrophotography, will increase exposure times, | not likely to catch on since it only works for astrophotography. | Unless entire cities, including parking lots, adopt them, it will | only help with direct stray light, which isn't that much help. | tdubhro1 wrote: | Great idea and demo but tough to see many municipalities | refitting their street lighting to keep astronomers happy. Might | be easier to persuade them to just turn streetlights off | completely for a few hours a night, at least then there's some | cost saving. | | Maybe in the future when we all have smart glasses with night | vision mode and self driving cars we'll look back at citywide | streetlights as a quaint and inefficient solution | nightowl_games wrote: | > we all | | A common mistake technologists make is to conflate the | technologically illiterate with the entirety of the population. | I can't overstate how technologically stratified we are and I | believe his trend will only worsen. As technology advances, we | will see the literate move forward and the majority stay | relatively still. We will only see further stratification. We | must assimilate this truth into our strategy. | wruza wrote: | Ah, the good old "human eye can't see N Hz" that will make night | lights insufferable for those who happen to see it. My grandma | has a couple of lightbulbs in her apartment that annoy _nobody_ | except me. I feel like laser-blinded when they are on, no matter | where I look. It 's blindingly bright and visually dark. Idk if | it's flicker frequency or light spectrum tbh, but it's that same | "hey you shouldn't see it, cause nobody can" attitude. I also | shouldn't see quick static-y shimmering on any lcd panel, because | their backlight frequency is in a range that my eye couldn't even | register. | mdturnerphys wrote: | I wonder if your eyes move around a lot. It's known that we can | see flicker in things like LEDs on a clock when our eyes move | fast enough that subsequent flashes are sufficiently separated | in the field of vision, particularly in our peripheral vision, | and I've also experienced this with LED headlights while | driving. | continuational wrote: | > It's blindingly bright and visually dark | | Well put. You can easily see flicker if you wave your hand in | front of a flickering light source. The trail of your hand will | look discrete, rather than continuous as it does with natural | lighting. | zoky wrote: | Most LEDs already blink at high frequencies to control power | output. This idea just synchronizes the blinking. | bombela wrote: | I experience the same "blinding bright but visually dark" on a | battery powered light I own. I wonder if it depends on the | length of time the light is off. | | Most light that flicker below 400hz really bother me, but I | still perceive the surrounding as illuminated. While this | particular torch light feels like "blinding darkness". | cm2187 wrote: | Dogs apparently see at a higher frequency. For those who want | to torture animals... | jcalvinowens wrote: | I feel the same way. If I'm sitting still I find I don't care | much... but if I'm working with my hands and moving around it | drives me crazy and gives me headaches, especially if I'm | focusing on something spinning. | | Just for fun, I replaced the LED dimmer in my garage with a | homemade board that has a frequency knob in addition to a duty | cycle knob. I've found that the cutoff for bothering me is | around 10KHz, which is far higher than I'd have ever expected. | zokier wrote: | > But there is a downside to LEDs: They're much brighter than | old-fashioned energy-guzzling light bulbs. | | Such a weird statement to make. LEDs are not somehow intrisically | brighter than other light sources, it is simply a design | parameter. If new LED lights are brighter than whatever they | replaced, it is because someone purchased lamps with higher light | output, not because they are LEDs. You can get plenty bright | without LEDs too. | herodotus wrote: | I think what is more accurate is that the frequency spectrum of | typical LED street lights makes them seem brighter (much more | blue). | Throwfi44 wrote: | Too complicated, just let it blink at 50hz and synchronise with | electric grid! | lencastre wrote: | Light manufacturers hate this simple trick: | | Turn off the lights. | persnickety wrote: | > But there is a downside to LEDs: They're much brighter than | old-fashioned energy-guzzling light bulbs. | | Are light bulbs actually being used in street lighting? I can't | recall ever seeing that. Typically there's some gas-discharge | lighting for that, and as far as I know, good old sodium-vapor | lamps are pretty energy-efficient, on top of being not-terrible | for astronomy. | | This makes me wonder: what are LEDs replacing? And why are LEDs | being installed rather than sodium-vapor lights? Is it because | they are whiter? Cheaper to install? Just more hip? | fragmede wrote: | Cheaper to operate, which over an entire city's worth of street | lamps is very material. Sodium-vapor lights eventually need to | be replaced (as do LEDs), so why not replace them with a modern | technology that's cheaper to operate? | canoebuilder wrote: | > _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 photons" instead banking the savings and | maintaining nighttime lighting at non eyeball scorching | levels. | qmarchi wrote: | 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... | canoebuilder wrote: | 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. | the_third_wave wrote: | One of the advantages of low-pressure sodium lamps is that they | emit nearly all their light in a narrow spectrum which is easily | filtered out. This leads to non-existent colour rendition - | everything is seen in shades of warm orange - but given that | these lamps have been used for decades without too many problems | this seems to be a surmountable problem, at least on motorways | which are a major source of light pollution. | | If monochromatic orange light is deemed undesirable it might be | worth experimenting with mixing three monochromatic red, green | and blue sources which also can be filtered out. The combination | of the three produces something close to (but not identical to) | white light which provides better colour rendition. | cogman10 wrote: | It's a bit weird that LEDs street lights didn't mimic the color | profile of the sodium lights they are replacing. | | In fact, I think it's a bad thing. Night vision is better | preserved with warmer colors. The bright blue daylight color | kills our night vision which ultimately results in temporary | blindness as we move away from the street light. | dreamlayers wrote: | I think a big part of the problem is use of cool white LED | lights, which produce more light on the blue part of the | spectrum. That light scatters more in the atmosphere, like how | the sky is blue during the day. | | Around here, the LED lights do not seem brighter like the article | claims. | | Also, they are all full cutoff. In the past, almost all high | pressure sodium streetlights meant to send light downwards had a | glass globe below, which sent some light upwards. LED | streetlights have flat panels instead, so none of the light | fixture itself can directly send light into the sky. Only light | reflected from illuminated objects and scattered by the air can | light up the sky. | coffeedan wrote: | More accurate title: "Non-simple streetlight hack could protect | cameras and telescopes from urban light pollution, but still | annoy anyone outside just trying to look at the stars" | nativeit wrote: | Astronomers already use a variety of optical filters, and LEDs | tend to be "spectrally peaky". If we standardized the spectrum | used in street light fixtures, it could very easily be filtered | out. I believe this has already been done when most street | lighting was sodium lamps, which is also a very narrow spectra. | mannykannot wrote: | 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/ | todfox wrote: | 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. | probably_wrong wrote: | 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. | johnea wrote: | 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... | amluto wrote: | 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. ___________________________________________________________________ (page generated 2023-11-18 23:00 UTC)