
Flagstaff, Arizona, switched to LEDs without giving astronomers a headache - lnguyen
https://arstechnica.com/science/2019/10/how-flagstaff-arizona-switched-to-leds-without-giving-astronomers-a-headache/
======
dmazin
> The bulbs Flagstaff relied on for most of its streetlights were low-pressure
> sodium—a variant that only emits light at a single wavelength (589
> nanometers) near that yellow color, producing something resembling
> candlelight.

Even 10 years after college I distinctly remember the look of Flagstaff at
night. Namely because the city was effectively grayscale and it was beautiful.

By the way, if you don’t know, Lowell Observatory in Flagstaff is where Pluto
was discovered.

~~~
nullc
> Even 10 years after college I distinctly remember the look of Flagstaff at
> night. Namely because the city was effectively grayscale and it was
> beautiful.

San Jose used to look that way too. There are still pockets of LPS lights here
and there, but since most makes are not commercially available anymore as of
this year you can expect they'll vanish fairly quickly.

Such a loss, LPS streelighting was very good. I hope the narrowband amber LEDs
are a commercial success.

Anyone know where there are fixtures with them available in small quantity?
... I stocked up on LPS bulbs before they went unavailble, but they won't last
forever.

~~~
emelski
I found that the LPS lighting in San Jose was very close in color to yellow
traffic signals, which made it sometimes confusing (and therefore more
dangerous) to drive there after dark.

------
berti
Aside from the sky glow aspects, I really dislike cool blue lighting. I've
just had my office upgraded to warm white LEDs and it's really noticeable
every time I walk into a colleague's office with "cool daylight" coloured
lighting.

~~~
9HZZRfNlpR
I very much prefer working in cold white and whee I relax and rest there I
prefer warm white. I think cold white helps me stay awake and more alert. It
all might be s placebo of course.

~~~
Cthulhu_
No that's actually proven science; white or blueish lights help you wake up /
stay awake, whereas orange / red lights will help you relax / sleep / produce
melatonin. It's why F.lux and the native solutions shift screens to red at
night. It's really quite stark a difference if you turn that off at night.

~~~
behringer
It's far from proven science.

~~~
authoritarian
There are lots of studies and articles discussing the affects of blue light on
melatonin and sleep

[https://www.ncbi.nlm.nih.gov/pubmed/30311830](https://www.ncbi.nlm.nih.gov/pubmed/30311830)

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2717723/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2717723/)

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831986/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831986/)

[https://www.health.harvard.edu/staying-healthy/blue-light-
ha...](https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-
side)

[https://www.sleepfoundation.org/articles/how-blue-light-
affe...](https://www.sleepfoundation.org/articles/how-blue-light-affects-kids-
sleep)

[https://www.healthline.com/nutrition/block-blue-light-to-
sle...](https://www.healthline.com/nutrition/block-blue-light-to-sleep-better)

[https://brighamhealthhub.org/prevention/using-light-
emitting...](https://brighamhealthhub.org/prevention/using-light-emitting-
devices-before-bed-may-impact-sleep)

[https://www.scientificamerican.com/article/q-a-why-is-
blue-l...](https://www.scientificamerican.com/article/q-a-why-is-blue-light-
before-bedtime-bad-for-sleep/)

~~~
behringer
[https://www.ncbi.nlm.nih.gov/pubmed/30311830](https://www.ncbi.nlm.nih.gov/pubmed/30311830)
No real conclusions. It's appears to be a study aimed at making future studies
better "The review enables further development of an evaluation method of
light pollution in LCA regarding the light-induced impacts on human circadian
system."

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2717723/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2717723/)
No definitive conclusions: "Additional laboratory-based and field studies are
still necessary to better understand some features of the human circadian
response to light. We are only beginning to understand how prior exposure to
light affects the subsequent response to a light stimulus, and our
understanding of how light exposure can affect the period of the human
circadian system is also limited (135)."

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831986/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2831986/)
Seems to be a review of other research by a journalist

[https://www.health.harvard.edu/staying-healthy/blue-light-
ha...](https://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-
side) news article, not science

[https://www.sleepfoundation.org/articles/how-blue-light-
affe...](https://www.sleepfoundation.org/articles/how-blue-light-affects-kids-
sleep) News article, not science

I'd go through the rest but it's time for lunch.

------
rapnie
> “What's left is green,” Hall said. “And so you stand under this and it's
> like the zombie apocalypse, because everybody's green. They've gone to these
> in Hilo, Hawaii, and we were standing in a parking lot trying to talk to
> each other, and it's just like straight out of Night of the Living Dead.”

This is not my experience. In The Netherlands green LED's are applied more and
more often for streetlighting in rural areas and surveillance of building
construction sites (light pole + camera).

First time encounter takes some getting used to, because we are so familiar
with orange Sodium hue. But I find they make the night landscape more peaceful
and serene looking.

Green spectrum is perfect for the human eye. You see more detail and sharper
focus, seems to me (compared to orange). Apparently its also good for nature.
Not only to insects, but also birds not getting distracted.

~~~
jacobolus
Orange is a lot better if you want to keep your night vision and be able to
see into the shadows (or e.g. look at the stars with your unassisted eyes).

~~~
brandmeyer
Contrary to popular belief, cyan is better for night vision. Your rods are
most sensitive to cyan, so you can use much dimmer cyan light than you can use
red/orange light.

[http://stlplaces.com/night_vision_red_myth/](http://stlplaces.com/night_vision_red_myth/)

~~~
jacobolus
The question is not what you can see best with the least energy, but what kind
of glare in your peripheral vision will cause bright-adaptation.

Your page there seems to be based on its author looking at the sentitivity
curves for rods and cones and then speculating, but not as far as I can tell
based on experimental evidence about how well the eyes stay dark-adapted.

Edit:

Moreover, the type of lamps appropriate for medium-bright street lighting and
the type of lamps appropriate for briefly turning on to dimly see your camera
gear while you fiddle with it when you are out taking night-sky photographs
are quite different.

Disclaimer: I am not an expert on triggers for brightness adaptation. I should
try to hunt up some research papers sometime.)

Looks like
[https://www.osapublishing.org/josa/abstract.cfm?uri=josa-41-...](https://www.osapublishing.org/josa/abstract.cfm?uri=josa-41-6-402)
is a reasonable place to start looking into the citation graph.
[https://scholar.google.com/scholar?cites=4424978361272323417](https://scholar.google.com/scholar?cites=4424978361272323417)

Or maybe
[https://www.sciencedirect.com/science/article/pii/S004269897...](https://www.sciencedirect.com/science/article/pii/S0042698977800011)
[https://scholar.google.com/scholar?cites=1469411636090158094...](https://scholar.google.com/scholar?cites=14694116360901580947)

------
retSava
This year we (our family) have the expressed goal of renting a cabin far off
from major cities (partly) so our daughter will get to see a night sky full of
stars.

We live close to an airport, so atm she gets excited by seeing more than
10-ish stars, so I'm looking forward to seeing her reaction :). Also, once
seeing and pointing out a satellite was a highlight :).

~~~
daemin
One thing I'm thankful of when living and growing up in Australia, you could
clearly see the night sky and all the stars there if you went to the beach or
the hills. Far less ambient light pollution, such a beautiful night sky.

I just hope it doesn't get spoiled by all those constellations of Internet
Satellites.

~~~
ceejayoz
Australia has far less _air_ pollution, too, given the low population and
relatively tiny strip of populated areas along the coast.

The skies in Freycinet National Park in Tasmania were the most stunning I've
ever seen in my life.

------
snowwrestler
> Older streetlights are high-pressure sodium bulbs, which produce a warm
> yellow glow around a color temperature of 2,000 K... Many of the LED
> streetlights on the market have much cooler color temperatures of 3,000 or
> even 4,000 K.

I feel like referring to 2,000 K bulbs as “warm” and 5,000 K bulbs as “cool”
has got to be one of the worst screw-ups between scientific terms and common
terms in English. And probably a missed opportunity to embed some latent
understanding of thermodynamics in the broader culture.

~~~
htfu
Warm/cool color theory predates the kelvin scale, so it might be more accurate
to say you feel Celsius' flipping his original scale was the screwup? But as
how it is now makes that much more sense, and since you couldn't really have a
kelvin version of such a thing anyways, maybe chalk it down as just one of
those things.

In any case no one could convince me to call the color of fire and the sun
anything but warm, and that of snow and sea cold.

~~~
wlesieutre
> _In any case no one could convince me to call the color of ... snow and sea
> cold._

How about the color of a gas stove flame?

Maybe we should have called them "warm white" and "hot white" instead.

~~~
htfu
Yeah warm to hot is good but again runs into clashing with things established
before much had been said about black-body radiation.

Just because it might not be conductive to a neat 1:1 mapping with scientific
common sense doesn't have to mean either should change. Quirks are fun!

~~~
wlesieutre
I'm used to it myself, but I work in architectural lighting and I can't count
how many times I've had to explain that "warm white" is the low temperatures
and "cool white" is the high temperatures. It's a frequent nuisance for me,
but not a huge deal and we're stuck with it.

If we were going to make people put in some effort and redefine fix stupid
quirks that exist out of historical convention, I'd put that effort toward
adopting metric instead of switching words for shades of white :P

It's not like switching cool and hot would make sense either, 2700K
(orangeish) is 4400°F and 5000K (blueish) is 8540°F. Neither of those is
anything near a "cool" temperature. "Blazing white" and "inferno white"?

~~~
htfu
Exactly what I mean, it's never going to make perfect sense, so trying to
adapt two separate meanings to gel slightly better seems futile.

I would argue the US still not being on SI is a bit more than a quirk. I
wonder whether you'll have completed metrification by the end of the century.

------
Merrill
Are there no orange/yellow LEDs? Seems odd, since LEDs were red long before
other colors were available.

Years ago, Pickett slide rules were a greenish yellow, which, according to
their advertising, was the color that provided the sharpest visual acuity and
comfort for the user. Maybe that would provide the best vision for the least
lumens as well.

~~~
gmiller123456
>...was the color that provided the sharpest visual acuity

I think it changes considerably based on the environment and the user. I do
some 10 meter air rifle competition, and the sighs have filters in them to let
you choose different colors. I can notice a big difference based on the
lighting, and at a competition different people will have settled on different
colors.

------
_Microft
That's not only dark-sky- but also insect-friendly! Insects are attracted by
blueish lights which, for example, the old sodium pressure lamps did not emit.
(The orange light you might remember from those were the 589nm double spectral
lines of sodium.) LEDs can/do emit blueish lights and should be picked
carefully for outdoor lighting.

------
sparker72678
It’s a real shame that Phoenix metro is going to ruin everything for Flagstaff
and Tucson in the not-too-distant future by refusing to implement any light
limits at all.

~~~
driverdan
How is that going to ruin things for Flagstaff? Phoenix is far away from
Flagstaff.

~~~
sachdevap
Dark skies require a pretty high radius of dark landmass. For an estimate of
the extent of this, try seeing the areas around major cities here:
[https://www.lightpollutionmap.info/](https://www.lightpollutionmap.info/)

------
post_break
I can't stand the orange glow of old street lights. You can see so much better
with 4300k vs 2000k
[http://i.imgur.com/JsSCfFp.jpg](http://i.imgur.com/JsSCfFp.jpg)

[https://www.youtube.com/watch?v=U1dMlVwUsrA](https://www.youtube.com/watch?v=U1dMlVwUsrA)

~~~
simonebrunozzi
There are places where I would strongly disagree with you, like my home town
Assisi, in Italy [0].

But for everything else, you are quite right.

[0]:
[https://www.flickr.com/photos/126687494@N08/15010177954/](https://www.flickr.com/photos/126687494@N08/15010177954/)

------
pkaye
Flagstaff is the only city so far I've actually been able to see the milky
way. We just got lucky one night while visiting as the sky was clear at the
Lowell observatory.

------
seanalltogether
> Another way to do it is with phosphor coatings on the LED that absorb light
> of one wavelength and emit it at another wavelength. Lights known as
> phosphor-converted amber (PCA) shift all the light out of the blue and into
> the yellow part of the spectrum at the cost of some efficiency.

Is this essentially an LED filament bulb? I've replaced all lights in my house
now with LED filaments because they look more natural and are omnidirectional.

~~~
theatrus2
It has nothing to do with filaments and is all with the phosphor coating.
Standard white LEDs intentionally bleed the base blue LED through, whereas PCA
LEDs do not.

Lumileds is the primary innovator for PCA (and other offshoots).
[https://www.lumileds.com/uploads/571/DS144-luxeon-c-color-
li...](https://www.lumileds.com/uploads/571/DS144-luxeon-c-color-line-
datasheet-pdf)

------
codereflection
Seattle replaced all streetlights with LEDs a few years back. It too bad that
they are the blue lighting that the article mentions, which absolutely makes
viewing anything in the sky a lot harder than it already was. I'd love to go
back to Flagstaff some day to see the lighting in person.

------
notadoc
They also have a dark sky ordinance where various rules, to point lights
downward, covers over the tops of them, etc.

More cities should do this, it makes for lovely night skies where you can
actually see the stars.

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LinuxBender
Do the new street lights only have LED's, or do they also have cameras and
microphones like the ones installed in San Diego and a few other cities for
machine learning?

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Zamicol
[https://imgur.com/oYYRmHl.png](https://imgur.com/oYYRmHl.png)

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acollins1331
5k possy represent

