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Simple streetlight hack could protect astronomy from urban light pollution

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

#31

Post by canoebuilder »

fragmede wrote: post #29
persnickety wrote: post #28

> 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?…

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?

>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.

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

#32

Post by the_third_wave »

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.

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

#33

Post by klyrs »

bradley13 wrote: post #5

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

> 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.

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

#34

Post by Anotheroneagain »

cassianoleal wrote: post #23
Anotheroneagain wrote: post #16

Earlier quoted context omitted.

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.

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.

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

#35

Post by jcalvinowens »

wruza wrote: post #9

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 nobo…

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.

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

#36

Post by quietpain »

bradley13 wrote: post #5

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

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

Edit: https://www.mainsfrequency.com/

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

#37

Post by cogman10 »

the_third_wave wrote: post #32

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 pollutio…

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.

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

#38

Post by cassianoleal »

Anotheroneagain wrote: post #34
cassianoleal wrote: post #23

Earlier quoted context omitted.

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.

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.

> 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.

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

#39

Post by cassianoleal »

canoebuilder wrote: post #30
cassianoleal wrote: post #23

Earlier quoted context omitted.

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.

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.

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

#40

Post by eszed »

Anotheroneagain wrote: post #34
cassianoleal wrote: post #23

Earlier quoted context omitted.

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.

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.

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.

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