[HN Gopher] Simple streetlight hack could protect astronomy from...
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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.
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