Simple streetlight hack could protect astronomy from urban light pollution(space.com)
space.com
Simple streetlight hack could protect astronomy from urban light pollution
https://www.space.com/astronomy-light-pollution-streetlight-hack
158 comments
I often wonder how cutting and folding a bit of sheet metal and bolting it onto the streetlight as a shroud is overlooked whenever streetlights are built or repaired. There's one that shines directly into my bedroom but there's no good reason for it to illuminate any part of the building I live in.
Try contacting your city about it. Here they will come around within a few weeks and do as you suggested if you complain.
Yep. This is low hanging fruit for making constituents happy. I emailed my city councilor about this because I couldn't figure out who to ask at public works. The next morning a work truck rolled up and installed a shield on the light nearest to my house.
Yes they did this for my parents house. A guy with some sheet metal and a shears.
Its often the most offensive shade of bright white fluorescent-like LED. Why can't they do the orange one that lets everyone be ok seeing light at night and sleeping to tell the tale
LED it's more power efficiencient . However, there are LED light bulbs that have some kind of filter that makes it more ambient and astronomy friendly. Normal white LEDs are a nightmare for astronomy, because his light spectrum it's hard to block with any kind of "anti light pollution" filters.
Its basically prison light, I would only ever use it to wake up in the morning. Anybody who seriously uses it to save money in a frequented space or in place of proper soothing ambient light is a bit off in my view. It makes me unhappy and feel beyond agitated whenever I am compelled to be around it.
2800k LEDs are not filtered white light afaik.
A bit of background for those who may not be aware, white LEDs are UV LEDs with a white light emitting phosphor. I suspect 2800 K LEDs are a UV LED with a 2800 K light-emitting phosphor.
A bit of background for those who may not be aware, white LEDs are UV LEDs with a white light emitting phosphor. I suspect 2800 K LEDs are a UV LED with a 2800 K light-emitting phosphor.
Whats the orange one? I've seen pics of streetlamps like that unless its a MandelaEffect or somethint
You might be thinking of sodium vapor lights
Yes! Why doesn't everyone just use these? Where there's astronomical concerns or people agree its just a nice and worthwhile end to be able to see the night sky, maybe use the low-pressure sodium but yeah.
Edit: I wonder what gets used in "rich" places in contrast to "poor" places. I feel like rich people get the night sky and poor people get headaches and insomnia. So sick of this shit
Edit: I wonder what gets used in "rich" places in contrast to "poor" places. I feel like rich people get the night sky and poor people get headaches and insomnia. So sick of this shit
Is there any correlation between wealthy districts and poor districts in terms of type of light used? I feel like everyone would want to accomodate the rich areas and make sure they can see the night sky and sleep and not have the unpleasent "poor" flurorescent/led "cost-savings" light
I wonder if some jurisdictions assume people prefer having the light go far and wide, for security / safety.
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?
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?
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.
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.
Okay, let's do some math. Very rough napkin numbers, but it'll get us close.
A 150Hz blink rate means a period of 1/150s, or ~6.7ms.
The speed of radio signals through air near the surface is a bit lower than c, let's call it 299,250 km/s. [0]
When you multiply those numbers you get ~1500km. That means each 'on' and 'off' signal is 1500km long, moving near c. More specifically, the signals are concentric rings around the transmitter 1500km in width.
Let's look at London. I picked it at random, but it just happens to have a land area around 1500km^2. Assume the transmitter is in the center of the perfectly circular city, that means it takes 3.3ms for each 'on' and 'off' signal to cover the entire city. Each on and off pulse is just about exactly long enough to cover the entire city.
All that together means that at any given moment 50% of the lights in the city are on, and the other 50% are off. That's about as far from synchronized as you can get, really.
Also, light is slightly faster than radio in these conditions[1]. The light reaching the center of the city won't be pulsing in the same phase as the signal you're sending out. It will also be blurred and muddied due to the difference in signal speed. You probably wouldn't see much flicker in the light at all, as 50% of the lights are always on. On average, you receive 50% of the light you would otherwise, but that value will never reach 0. There won't be any periods of total darkness where you can make an observation, as the article suggests.
Moral of the story: light (and radio) is much, much slower than most people realize.
[0] https://ieeexplore.ieee.org/document/170108 [1] I couldn't find a confident number in my 16 seconds of searching. Seems like just a few percent faster, but the real number doesn't matter here.
Bonus: you can synchronize the streetlights exactly, but it's much more expensive and complex than a single radio transmitter. You need to have every single light contain a receiver with an accurate clock that synchronizes with a geosynchronous satellite with an atomic reference clock. Search for "GPS disciplined oscillator" if you're curious.
A 150Hz blink rate means a period of 1/150s, or ~6.7ms.
The speed of radio signals through air near the surface is a bit lower than c, let's call it 299,250 km/s. [0]
When you multiply those numbers you get ~1500km. That means each 'on' and 'off' signal is 1500km long, moving near c. More specifically, the signals are concentric rings around the transmitter 1500km in width.
Let's look at London. I picked it at random, but it just happens to have a land area around 1500km^2. Assume the transmitter is in the center of the perfectly circular city, that means it takes 3.3ms for each 'on' and 'off' signal to cover the entire city. Each on and off pulse is just about exactly long enough to cover the entire city.
All that together means that at any given moment 50% of the lights in the city are on, and the other 50% are off. That's about as far from synchronized as you can get, really.
Also, light is slightly faster than radio in these conditions[1]. The light reaching the center of the city won't be pulsing in the same phase as the signal you're sending out. It will also be blurred and muddied due to the difference in signal speed. You probably wouldn't see much flicker in the light at all, as 50% of the lights are always on. On average, you receive 50% of the light you would otherwise, but that value will never reach 0. There won't be any periods of total darkness where you can make an observation, as the article suggests.
Moral of the story: light (and radio) is much, much slower than most people realize.
[0] https://ieeexplore.ieee.org/document/170108 [1] I couldn't find a confident number in my 16 seconds of searching. Seems like just a few percent faster, but the real number doesn't matter here.
Bonus: you can synchronize the streetlights exactly, but it's much more expensive and complex than a single radio transmitter. You need to have every single light contain a receiver with an accurate clock that synchronizes with a geosynchronous satellite with an atomic reference clock. Search for "GPS disciplined oscillator" if you're curious.
>Let's look at London. I picked it at random, but it just happens to have a land area around 1500km^2
Um am I really really tired and not reading correctly, or is this confusing linear area with square area? London doesn't stretch from New york to Florida.
186000 miles/second * pulse of .003 = 558 miles ~= 900 km
Um am I really really tired and not reading correctly, or is this confusing linear area with square area? London doesn't stretch from New york to Florida.
186000 miles/second * pulse of .003 = 558 miles ~= 900 km
I knew I fucked something up. Don't do math while smoking, kids.
Either way, propagation delay is a huge problem with synchronizing systems. It's not something you usually think about
Either way, propagation delay is a huge problem with synchronizing systems. It's not something you usually think about
Dont you have propagation delay in reverse too? Let's say you do turn off all the lights at the exact same time. The light hitting the telescope also travels at the speed of light.
There’s engineering feasibility, and then there’s feasibility. Is it any less feasible to operate fewer or dimmer street lights? How about directing light more efficiently? This is a problem of bureaucratic and societal engineering.
I was really just exploring a hypothetical. This whole idea of synchronizing lights is pretty dumb. It won't work, and even if it did it's still a bad solution.
Better solution is less lights, or turn them off at night or any of the other solutions we've been talking about for 30 years. Remember when street lights were killing sea turtles?
Better solution is less lights, or turn them off at night or any of the other solutions we've been talking about for 30 years. Remember when street lights were killing sea turtles?
I’m not a physics person, but couldn’t this be easily solved by adding a programmed delay that corresponds to the distance from the transmitter? Street lights aren’t known to migrate.
In principle, yes. But not easily.
The physics of radio wave propagation are surprisingly complex. Buildings and objects in the path between transmitter and receiver can cause various interference effects that basically slow down the signal. I'm glossing over a lot, but it would take significant effort to precisely measure the exact delay between any one receiver and the transmitter. It's much more complicated than just the distance, and each one has to be measured individually.
I'm not an expert in RF, but I think this concept of a single synchronizing transmitter just doesn't work in the real world. You'd probably build a cell network with many transmitters covering small areas. Each transmitter has the hardware to synchronize with thr others, and the lights just have a simple circuit slaved to the transmitter clock.
There's probably more clever ways to synchronize signals over long distances, but RF is black magic to me.
The physics of radio wave propagation are surprisingly complex. Buildings and objects in the path between transmitter and receiver can cause various interference effects that basically slow down the signal. I'm glossing over a lot, but it would take significant effort to precisely measure the exact delay between any one receiver and the transmitter. It's much more complicated than just the distance, and each one has to be measured individually.
I'm not an expert in RF, but I think this concept of a single synchronizing transmitter just doesn't work in the real world. You'd probably build a cell network with many transmitters covering small areas. Each transmitter has the hardware to synchronize with thr others, and the lights just have a simple circuit slaved to the transmitter clock.
There's probably more clever ways to synchronize signals over long distances, but RF is black magic to me.
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.
If the LEDs blink at 150 Hz, then a single on-off cycle has a "wavelength" of 2000 km.
The wavelength of the control signal doesn't seem relevant.
The wavelength of the control signal doesn't seem relevant.
Plus you just add a position based delay. This is quite the bikeshed!
How does the LED know its own position? At that point you might as well abandon FM and use GPS.
Send a few bytes of data onto the SD card on lamp installation. If GPS can do it all in one then that is probably better given how cheap the units are these day.
You must not be familiar with multipath interference. Radio isn't quite as synchronous as you believe it to be.
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?
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?
> Right. They're going to get all the streetlights in an entire city to blink in unison. Sure they are.
The article states they use GPS for synchronization. I wish they went into it further, but a number of affordable chipset can do emit PWM at the proposed frequencies, globally aligned in time to PPS(every receiver computes the same top of second), then the telescope exposes during the blanking time.
On a related note I have a 1MHz GPS time source in my office that is synced to a 10MHz OCXO(more common for test gear) so my equipment is phase synchronized to GPS. It's really spooky to sync the oscilloscope to one time source and probe another time source with the scope and watch how their phases don't perceptibly drift from each other.
The article states they use GPS for synchronization. I wish they went into it further, but a number of affordable chipset can do emit PWM at the proposed frequencies, globally aligned in time to PPS(every receiver computes the same top of second), then the telescope exposes during the blanking time.
On a related note I have a 1MHz GPS time source in my office that is synced to a 10MHz OCXO(more common for test gear) so my equipment is phase synchronized to GPS. It's really spooky to sync the oscilloscope to one time source and probe another time source with the scope and watch how their phases don't perceptibly drift from each other.
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.
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.
Precisely. Why go for the complex, expensive, and fragile solution when better shades (and maybe proximity/motion sensors) would do the job?
Where I live they installed street lights that are a lot dimmer by default, but they are connected and have motion detectors. Whenever someone comes near, the light gets brighter and so do the others in direction of travel. You kind of get a light wave traveling with you and afterwards they dim again.
The mayor then got complaints that the street lights are not as bright as mandated by some regulation (when measured with an empty road in their dimmed state ...).
The mayor then got complaints that the street lights are not as bright as mandated by some regulation (when measured with an empty road in their dimmed state ...).
> 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.
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 those.
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.
> 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]?
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]?
No it's a horrible idea, imagine the lights turning on and off as people pass. No!
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.
I believe relatively dim, warm coloured lights are a much better idea.
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.
> 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.
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.
>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.
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.
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.
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.
> 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.
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.
>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.
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.
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.
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.
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.
The problem is that warm lights just look dimmer than they are in reality, you need objectively much brighter warm light to see anything at all. 505nm is a commonly available wavelength that is very near the eye's peak sensitivity in the dark, so a very low powered light would provide sufficient light, and it wouldn't be more overstimulating than moonlight unless it's way too bright. The only drawback it seems to have is that it's rather close to the O-III astronomical filter, I don't know how much it matters.
I think their point is that all the wavelengths that make the lights most-useful from a safety perspective are also those which interfere with seeing the stars and whatnot.
Low pressure sodium is useful for safety (you don't need color vision to see the shadow of an attacker, a fallen branch, shiny reflective shards of a glass bottle, or a pothole), efficient (Lumen/W), and extremely tame for star-observing (look through a narrow-band filter to block the two very thin very close spectral lines (so close you need decent instruments to see that its not just a single one)).
The downside is that you don't get color vision, because the light is so close to monochromatic that you might as well think of it as truly monochromatic for human vision purposes.
Ok, but that's where I'm confused. You don't need to see everything in full colour and detail to be safe. You need to be able to make out shapes, movements and shadows.
A few years ago I lived in a neighbourhood where all the street lights had a dark yellow tint, very warm coloured. They weren't all that bright either. I could see a person a block away with ease.
Again, that was far from ideal to read a book, but why would I do that out on the streets at night?
A few years ago I lived in a neighbourhood where all the street lights had a dark yellow tint, very warm coloured. They weren't all that bright either. I could see a person a block away with ease.
Again, that was far from ideal to read a book, but why would I do that out on the streets at night?
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.
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.
Even worse is
Why pay to occasionally faintly illuminate the bottoms of airplains ever?
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
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/
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.
Why not, just sync them to the AC power grid they're all powered from.
Different types of transformers introduce different phase shifts.
Couldn't you still account for offset?
Maybe? I guess you could "calibrate" it with GPS. I don't know how consistent the phase at a specific location really is in practice on long timescales.
> 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.
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.
I find it difficult to believe that a city-wide distributed synchronization algorithm could actually work. How do you deal with the photo-electronic-photo propagation delay, and ensure that each sensor is paying attention to the correct emitters, possibly including itself?
Even if you somehow got it to work, one guy with a hacked flashlight could throw the whole thing into chaos.
Even if you somehow got it to work, one guy with a hacked flashlight could throw the whole thing into chaos.
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.
They need phase locked too. Edit: article says they're using GPS, probably using PWM-aligned-to-PPS.
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
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
Get real. If we can’t get municipalities to limit light pollution with simple common sense measures like directing light more efficiently and dimming/turning off lights when they’re not needed, how can we expect them to synchronize their lights with a GPS driven signal? Never mind that this “simple” fix does nothing to address the everyday societal impacts of light pollution.
> 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.
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.
I think what is more accurate is that the frequency spectrum of typical LED street lights makes them seem brighter (much more blue).
Just about any place that I've seen sodium lights replaced with LEDs, they have been replaced with vastly brighter LEDs. Maybe sloppy writing, I think the article is referring to the LED installations being brighter than the installations they are replacing.
Seeking advice on how to lobby my city to disable a streetlight. We are on a rural road next to conservation land, and it blasts our house with light through the night, distracting our son with autism. Considering getting an instrument to measure the light's intensity and gathering data. Any tips on how to lobby a city government with such an unusual request would be greatly appreciated.
Just shoot it. It'll never get noticed.
I'm not going to advocate for illegal activities but unfortunately this is the most practical solution in most of the US.
That said, do NOT shoot anything with a real firearm. Even small caliber bullets travel for miles. Walking out at 2am with a red ryder BB gun and plinking it would work just fine.
That said, do NOT shoot anything with a real firearm. Even small caliber bullets travel for miles. Walking out at 2am with a red ryder BB gun and plinking it would work just fine.
You can usually ask the utility to add a light shield. Just about every model can take one to reduce glaring sideways light.
They may also be willing to put it on a timer.
Or, depending how rural it is and how daring you are, you could put it on a timer yourself.
Or, depending how rural it is and how daring you are, you could put it on a timer yourself.
Do all that but have you considered good blinds and maybe even a sleeping mask? I'm on your side but good tools to have for anyone, particularly with or without such a condition. The sleeping mask Tim Ferriss recommends is amazing, I hate sleeping without it
Also make sure he makes his phone/screen orange-tinted at night and let him pick out an album or book he loves and teach him to listen to it every night. Slow down the speed as far as he'll tolerate and set a sleep-timer for like 1.5h to fade it out. Also, turn down the volume just so he can barely hear it and has to strain a bit to hear it.
Nothing much to add but you have three options as suggested by others:-
1.) the subservient: Get a good sleeping mask and blinds for your son 2.) the cooperative: work with the utility to put on a light shield 3.) the libertarian: shoot it
Human nature, encompassed in one thread. Beautiful, I love this site.
1.) the subservient: Get a good sleeping mask and blinds for your son 2.) the cooperative: work with the utility to put on a light shield 3.) the libertarian: shoot it
Human nature, encompassed in one thread. Beautiful, I love this site.
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.
I see the problem as completely opposite. Streetlights ruin your night vision so you can't see in all the dark areas people could be hiding.
I used to live in a pretty bad area, and the darkest roads were safest because creeps couldn't see what they were doing
I think that's a bit sexist. While criminals will prey on people they think are weak and that often includes women, that's not exclusively so. I don't know that someone who is vulnerable would really be any safer in a well lit street at night, depending on other circumstances of course.
Cars have headlights. It could be that pedestrians can carry lights too. We could reduce infrastructure costs, electricity costs, allow pedestrians to be more conspicuous, and reduce the other negative impacts of constant lighting. You could even fund these personal lights for lower income people with the infrastructure savings.
Cars have headlights. It could be that pedestrians can carry lights too. We could reduce infrastructure costs, electricity costs, allow pedestrians to be more conspicuous, and reduce the other negative impacts of constant lighting. You could even fund these personal lights for lower income people with the infrastructure savings.
> It could be that pedestrians can carry lights too
Aye, on my midnight walks when I can't sleep (middle of nowhere - no streets, never mind street lights, it's all trails and fields. Amazing for stargazing!) I use my watch in flashlight mode to see where I'm going wherever it's particularly pitch black. I've also got a backup make-everything-daytime strength torch on me too if I need to properly see something or take out someone's night vision long enough to leg it
Never needed to use the latter so far. I don't imagine anyone trying to prey on me would even see me (or me them) until they're right up close if I turned the watch light off.
Fun tidbit for any new midnight walkers: Your night vision is separate in each eye. If you do need to use a light source in the dark, close an eye before you turn it on. That way when you turn it off you can open the eye and still mostly see where you're going while the other eye catches back up :)
I learned it doing backstage work at a theatre, I also heard it's the actual use case for pirate eye patches -- swap eye when going above and below deck. Good times.
Aye, on my midnight walks when I can't sleep (middle of nowhere - no streets, never mind street lights, it's all trails and fields. Amazing for stargazing!) I use my watch in flashlight mode to see where I'm going wherever it's particularly pitch black. I've also got a backup make-everything-daytime strength torch on me too if I need to properly see something or take out someone's night vision long enough to leg it
Never needed to use the latter so far. I don't imagine anyone trying to prey on me would even see me (or me them) until they're right up close if I turned the watch light off.
Fun tidbit for any new midnight walkers: Your night vision is separate in each eye. If you do need to use a light source in the dark, close an eye before you turn it on. That way when you turn it off you can open the eye and still mostly see where you're going while the other eye catches back up :)
I learned it doing backstage work at a theatre, I also heard it's the actual use case for pirate eye patches -- swap eye when going above and below deck. Good times.
> Your night vision is separate in each eye.
As a kid, I also learned your eyes will individually adapt to not only brightness, but color.
The front door to the house was open and I put my face with my nose along the edge of it. One eye faced indoors, one eye faced outdoors. After a short amount of time I pulled my face away and it was quite clear that color in each eye had adapted to what it was seeing.
fun but weird.
As a kid, I also learned your eyes will individually adapt to not only brightness, but color.
The front door to the house was open and I put my face with my nose along the edge of it. One eye faced indoors, one eye faced outdoors. After a short amount of time I pulled my face away and it was quite clear that color in each eye had adapted to what it was seeing.
fun but weird.
Maybe, but I have also heard this opinion independently from a few women in my life.
Yeah, I'm simply pointing out that anecdata can contribute to stereotypes. In the way the OP posted it, it sounded like 'men are ok with dark streets, but women are the reason we can't make the streets dark'. When in reality the line isn't on sex but other things like strength and defense knowledge. As I mentioned before, those sorts of things might be more associated with one sex or the other, but it's a mistake to stereotype.
I think it's a bit like radar and sonar.
Receiving bounced waves gives you information, while emitting it gives out information, and may make you a target. A streetlight is a neutral-emitter that doesn't usually need to worry about being attacked, unlike a bobbing flashlight held by someone walking in the dark woods.
A difference with car-headlights is that the car itself is a protective shell, and it's hard for other cars to hide in bushes.
Receiving bounced waves gives you information, while emitting it gives out information, and may make you a target. A streetlight is a neutral-emitter that doesn't usually need to worry about being attacked, unlike a bobbing flashlight held by someone walking in the dark woods.
A difference with car-headlights is that the car itself is a protective shell, and it's hard for other cars to hide in bushes.
Street lights still have shadows and areas that they don't cover. You still have things like the opposite side of cars that you can't see even if you have a street light (ie your bushes example applies with or without street lights). When I say to carry a light, I don't mean the light on your phone, but a proper means of illumination. If done correctly, this would provide plenty of information before in attack range (assuming you're not getting shot at long range, which isn't really an issue in common crime today). There are also defensive tactics with the lights that can benefit you. For example, if someone is waiting in the dark for you (as your comment implies) and you blast them with 1200+ lumens maybe even in strobe mode, you now have the advantage, streetlight or not.
So yeah, you can give out some information by holding a light, mostly about position. You give out much more information being in the light from street lights, such as sex, age, weakness/disability, etc that are more useful to criminals.
The are plenty of areas without street lights or with minimal street lights today. The primary issue as it pertains to crime is not a lack of street lights, but other factors such as socioeconomic factors and defensive knowledge.
So yeah, you can give out some information by holding a light, mostly about position. You give out much more information being in the light from street lights, such as sex, age, weakness/disability, etc that are more useful to criminals.
The are plenty of areas without street lights or with minimal street lights today. The primary issue as it pertains to crime is not a lack of street lights, but other factors such as socioeconomic factors and defensive knowledge.
I don't understand why not just use a motion sensor, and turn the nearest 10 or so lights where the motion sensor was activated for a few minutes.
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.
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.
> 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?
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?
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?
Actually they aren't in terms of energy. High pressure sodium lamps output around 100 lumens per watt, which is the same as LEDs.
I'd imagine some LED luminaries are consuming more energy than the sodium lamp they replaced, as they are usually brighter and some will have terribly inefficient power supplies.
I'd imagine some LED luminaries are consuming more energy than the sodium lamp they replaced, as they are usually brighter and some will have terribly inefficient power supplies.
Common low pressure sodium and white LED street lights are about the same in efficiency: around 140 lm/W. LED street lighting pollutes the night sky with light that astronomers find impossible to fully compensate for, impacts wildlife (and probably not in a good way), inhibits low-light vision adaption in drivers and pedestrians, and gives public areas all the attractiveness of an operating theatre. All this for a dubious promise of savings after tens of millions of initial investment from each local authority.
>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.
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.
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...
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.
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.
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.
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.
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.
Could it be that you inadvertently smoothed the visual flicker on the electrical side? Consider fast brightness sensor with known (ideally approximately linear) sensitivity to the AC component of brightness, and check with an oscilloscope or so. A soundcard with 96 kHz sample rate should probably have a high-enough filter cutoff to be quite and easily useful there, though I'd see to check the frequency response with an edge generator to confirm that it has linear sensitivity from low-ish frequencies to the >=10 kHz ones of particular interest.
That's a great point: above some frequency, the inductance of the system starts to average the voltage like the output of a switching power supply.
I did think of that: I used a camera with a rolling shutter image sensor and manual exposure settings to prove to myself the LEDs were really still getting the full swing at higher frequencies. Also, to be clear, I'm talking about 12VDC COB LEDs with hard on/off PWM dimming, not A/C ripple.
I don't know, but I'd expect the cutoff frequency to be a lot higher. The self inductance of 30ft of 16awg wire is about 20uH. I should test it...
I did think of that: I used a camera with a rolling shutter image sensor and manual exposure settings to prove to myself the LEDs were really still getting the full swing at higher frequencies. Also, to be clear, I'm talking about 12VDC COB LEDs with hard on/off PWM dimming, not A/C ripple.
I don't know, but I'd expect the cutoff frequency to be a lot higher. The self inductance of 30ft of 16awg wire is about 20uH. I should test it...
You should consider talking to the researchers who developed IEEE 1789. 120 Hz is problematic for many people, but 10kHz seems unusual unless you’re a camera.
It's specifically fast spinning objects that get me: I was spending a lot of time staring at a 3400rpm grinder wheel with a fine repeating pattern on it.
If I'm just sitting typing on my laptop, even the 120hz ones don't bother me.
If I'm just sitting typing on my laptop, even the 120hz ones don't bother me.
> 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.
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.
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".
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".
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.
Dogs apparently see at a higher frequency. For those who want to torture animals...
Most LEDs already blink at high frequencies to control power output. This idea just synchronizes the blinking.
How about we just get rid of streetlights. They only make it harder to see everywhere around that isn't directly under a streetlight and are a waste of energy and effort.
I believe several UK cities tried that kind of thing during the last WW. Didn't turn out great for the pedestrians (and also cars had restricted lighting, too).
"Put that bloody light out!"
I recently spent a week in Sisters, Oregon (where Thompson Guitars is making me a beautiful walnut guitar which I can't wait to play for y'all at future tech conferences).
I fell completely in love with the city on my first evening there. It took me a few hours to realize why: there are almost no streetlights. The main drag (Cascade Ave) has tasteful, downward-angled, orange lights. And the rest of the city has none at all. And. it's. awesome.
You can be standing in the middle of joyous nightlife, in earshot of two different live bands, and still see a stunning sky full of high desert stars. Each business lights their little strip of sidewalk as they see fit.
And it really hit home: It's 2023. The idea that light is an essential safety feature is one whose time has past. 90% of folks have a flashlight on their phone at the ready, and for anyone who doesn't have that privilege, or whose battery is dead, getting light shone in one's direction is as simple as shouting, "help me! I need light over here now!"
Being around the edges of the city at night is absolutely marvelous, especially on a bicycle.
Sisters has ignited in me a belief that streetlights are on their way out - coming to a city near you.
I fell completely in love with the city on my first evening there. It took me a few hours to realize why: there are almost no streetlights. The main drag (Cascade Ave) has tasteful, downward-angled, orange lights. And the rest of the city has none at all. And. it's. awesome.
You can be standing in the middle of joyous nightlife, in earshot of two different live bands, and still see a stunning sky full of high desert stars. Each business lights their little strip of sidewalk as they see fit.
And it really hit home: It's 2023. The idea that light is an essential safety feature is one whose time has past. 90% of folks have a flashlight on their phone at the ready, and for anyone who doesn't have that privilege, or whose battery is dead, getting light shone in one's direction is as simple as shouting, "help me! I need light over here now!"
Being around the edges of the city at night is absolutely marvelous, especially on a bicycle.
Sisters has ignited in me a belief that streetlights are on their way out - coming to a city near you.
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/
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/
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.
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.
Pedestrian crossings in my city are illuminated by a bright blue light (only the width of the zebra crossing). I did not find that it made me more visible than another color, but obviously, I was not looking at my self from a distance.
is there a reason to prefer these blue lights? (that are a bit uncomfortable for the pedestrian, so there must be a reason)
is there a reason to prefer these blue lights? (that are a bit uncomfortable for the pedestrian, so there must be a reason)
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.
We could just use yellow LEDs. They have almost the same wavelength as low pressure sodium lamps (585 nm versus 589 nm).
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.
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.
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.
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.
Yellow LEDs have almost the same wavelength as low-pressure sodium lamps.
I wonder where the most dark, least light polluted location on earth is. I guess it's out on the ocean somewhere and not optimal for stargazing.
There are maps online [1],[2] that you can use. Oceans and deserts are the darkest, but national parks and sparsly populated areas are also a good choice. Of course, most of the time there’s nothing ‘nearby’ as population centers are always well lit.
[1] https://www.lightpollutionmap.info/
[2] https://djlorenz.github.io/astronomy/lp2020/
[1] https://www.lightpollutionmap.info/
[2] https://djlorenz.github.io/astronomy/lp2020/
If that is a "simple device", we can add it to computers to help synchronize time? For distributed databases it would be helpful
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
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
> 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.
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.
Easier would be to pick a standard monochromatic or RGB sources (no broad spectrum phosphors), and have them filter for those frequencies.
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...
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...
How will they sync the frequency onset of an entire city’s LEDs, so they all flicker on/off at the same moment? Or is the thinking here that it’ll average out and that will still be an improvement?
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"
Ludicrously complicated and expensive.
My own solution is all area lights, streetlights, headlights, etc be a standard monochromatic red, low-energy and night-vision-sparing.
My own solution is all area lights, streetlights, headlights, etc be a standard monochromatic red, low-energy and night-vision-sparing.
The hack is to make all lights in the neighborhood of an observatory flicker at “about 150 times per second”, and for observatories to ‘close their eyes’ when street lighting is on, giving up part of their light input (the article doesn’t tell, but I guess at least half of it. The LED lighting also will give up part of its brightness, but I think that’s less of a concern. It can easily be made brighter, if that’s needed at all)
I doubt that’s invisible to humans, though, and am fairly sure it is visible to many animals species, including some pets. https://en.wikipedia.org/wiki/Flicker_fusion_threshold#Displ...:
“For the purposes of presenting moving images, the human flicker fusion threshold is usually taken between 60 and 90 Hz, though in certain cases it can be higher by an order of magnitude.”
That’s already awfully close to 150Hz, certainly if all lights you see do that, but let’s ignore that, and read on, where we find:
“In some cases, it is possible to see flicker at rates beyond 2000 Hz (2 kHz) in the case of high-speed eye movements (saccades) or object motion, via the "phantom array" effect. Fast-moving flickering objects zooming across view (either by object motion, or by eye motion such as rolling eyes), can cause a dotted or multicolored blur instead of a continuous blur, as if they were multiple objects”
and
“The flicker fusion threshold also varies between species. Pigeons have been shown to have higher threshold than humans (100 Hz vs. 75 Hz), and the same is probably true for all birds, particularly birds of prey. Many mammals have a higher proportion of rods in their retina than humans do, and it is likely that they would also have higher flicker fusion thresholds. This has been confirmed in dogs.
Research also shows that size and metabolic rate are two factors that come into play: small animals with high metabolic rate tend to have high flicker fusion thresholds.”
TLDR: I don’t think this is a good idea, especially not given that the actual problem (FTA: “But there is a downside to LEDs: They're much brighter than old-fashioned energy-guzzling light bulbs”) is easily avoided. It’s not like we couldn’t replace light bulbs with LED lighting of equal intensity (and directed in the same directions)
I doubt that’s invisible to humans, though, and am fairly sure it is visible to many animals species, including some pets. https://en.wikipedia.org/wiki/Flicker_fusion_threshold#Displ...:
“For the purposes of presenting moving images, the human flicker fusion threshold is usually taken between 60 and 90 Hz, though in certain cases it can be higher by an order of magnitude.”
That’s already awfully close to 150Hz, certainly if all lights you see do that, but let’s ignore that, and read on, where we find:
“In some cases, it is possible to see flicker at rates beyond 2000 Hz (2 kHz) in the case of high-speed eye movements (saccades) or object motion, via the "phantom array" effect. Fast-moving flickering objects zooming across view (either by object motion, or by eye motion such as rolling eyes), can cause a dotted or multicolored blur instead of a continuous blur, as if they were multiple objects”
and
“The flicker fusion threshold also varies between species. Pigeons have been shown to have higher threshold than humans (100 Hz vs. 75 Hz), and the same is probably true for all birds, particularly birds of prey. Many mammals have a higher proportion of rods in their retina than humans do, and it is likely that they would also have higher flicker fusion thresholds. This has been confirmed in dogs.
Research also shows that size and metabolic rate are two factors that come into play: small animals with high metabolic rate tend to have high flicker fusion thresholds.”
TLDR: I don’t think this is a good idea, especially not given that the actual problem (FTA: “But there is a downside to LEDs: They're much brighter than old-fashioned energy-guzzling light bulbs”) is easily avoided. It’s not like we couldn’t replace light bulbs with LED lighting of equal intensity (and directed in the same directions)
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.
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.
Too complicated, just let it blink at 50hz and synchronise with electric grid!
Yay more strobing! More migraines! Isn't civilization great!
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.
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.
Also - it feels like it's not 'simple'. And I doubt it will ever be implemented.
Why do you think 150Hz is unacceptable? People used to watch 50Hz TV, and weren't bothered too much. And San Jose used to use 60Hz flickering streetlights (sodium? not sure) to reduce light pollution for Lick Observatory.
because tvs used phosphors it isnt really on/off 50hz just a slight light dip.
If you look at high speed footage of a CRT monitor, you'll see that only a few scan lines are lit at a time.
https://www.youtube.com/watch?v=3BJU2drrtCM&t=150s
https://www.youtube.com/watch?v=3BJU2drrtCM&t=150s
because of the high framerate you are seeing increased apparent contrast between actively lit and fading phostphors.
Pre-LED stadium lights do indeed flicker pretty egregiously, but, when correctly installed, they would be balanced between all three phases, so at least the average illumination was roughly constant.
I don’t know why TVs weren’t headache-inducing. Certainly old CRT computer screens were extremely unpleasant to look at at lower refresh rates.
I don’t know why TVs weren’t headache-inducing. Certainly old CRT computer screens were extremely unpleasant to look at at lower refresh rates.
IEEE 1789 lays a lot of that out. In a nutshell, LEDs are harsher.
Why not?
Even flicker that isn't perceptible to humans is still associated with increases in all sorts of things including eyestrain, headaches, anxiety, migraines, and seizures.
150Hz is well below the human perceptual threshold but still within the range that can cause problems.
150Hz is well below the human perceptual threshold but still within the range that can cause problems.
Thank you!
Because people can see the flicker. It becomes apparent with object moving quickly across your visual field (including waving your hand left-right). It creates big issues with photography and video recording.
Flicker at certain frequencies isn't noticeable to humans in isolation. Add in other types of flicker (lights at other refresh rates, monitors, TV's, etc) and you can see the interference between them.
Because of the rather well documented effects on health and visual performance.
When a bright light is extra annoying to light sensitive eyes it's because the lamp is actually blinking at a high frequency.
Because cities are made for people to live in.
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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