Unnecessary light on a field

My colleague Andrej Mohar recently shared this image with me:

This work by Andrej Mohar is licensed under a
Creative Commons Attribution-NonCommercial 4.0 International License.

The photo shows the light spread from single 20W 4000K LED that was recently installed. The lamp itself is designed to have no direct upward emissions (which is good), but much of the light is shining into an area which doesn't need to be illuminated (which is very bad), and even the area that is intended to be illuminated happens to be a region of very low traffic. It is so out of character for the region it is installed in, that at least two people in the nearby village have already officially complained about it.

In these sorts of cases, it doesn't matter how efficiently the lamp converts electricity into visible light. The light itself is unnecessary, so it is an inefficient use of electrical resources.

Milky Way and Skyglow from the Fürstein

Martin Würzer recently sent me this amazing panorama showing the skyglow over Switzerland:

Fürstein 360 Panorama v2 by Martin Würzer is available
under a CC BY-NC-SA license

He took the photo on New Year's Day 2017 around 8 pm, from the peak of the Fürstein. The light from Milan is visible at the far left. It's an amazing photo, and you can see it in full resolution by clicking on the name of the photo in the caption above.

Martin also sent me this image, which shows where at least some of that waste light is coming from:

Illuminated facade by Martin Würzer is available under a
Creative Commons Attribution 4.0 International License..

That photo was taken shortly before 3 am! There is some good news associated with this photo, however. By having a polite discussion with the architect and the firm that owns the building, Martin convinced them to remove the light that illuminates the facade, and to also improve the other lamps so that they produce less skyglow. Great job Martin!

For Swiss and other German speaking readers, Martin provided two useful references:

• The Swiss chapter of the International Dark-Sky Association
•  Recommendations from the Swiss Government for reducing light pollution

Spotlight on air

My colleague Martin Morgan-Taylor sent me this photo of a newly installed floodlight that doesn't actually seem to be pointed at a building facade, or really anything in particular at all.

Misdirected floodlamp by Martin Morgan-Taylor is licensed
under a Creative Commons Attribution 4.0 International License.

There are some flower beds nearby, but if they are meant to illuminate the flowers they are pointed in the wrong direction! (Incidentally, surely only someone who hates fireflies, glowworms, and other nocturnal insects would do such a thing, no?)

The design is such that the lamps will produce a lot of glare, making vision in the area worse. At the same time, about half of the light emitted is going to go up into the sky, producing skyglow.

One final, but really important point: It does not matter how "efficient" this lamp is in lumens/Watt. Almost none of the light produced by this lamp will assist humans with a visual task, so the true efficiency in the commonsense meaning of the word is near zero.

Tweetstorm about light pollution and citizen science

Why we can only track global changes in skyglow using citizen science. A tweetstorm by @skyglowberlin, submitted for publication on Twitter.

— Christopher Kyba (@skyglowberlin) March 8, 2017

First: what is skyglow? It's the artificial brightening of the night sky, due to artificial light. (Image from: https://t.co/6Yb1dzj7gv) pic.twitter.com/Lgsd2YWbbr

— Christopher Kyba (@skyglowberlin) March 8, 2017

On clear nights the scatter is from aerosols (dust, smoke, haze) and molecules (N2, O2). So more haze often means more skyglow.

— Christopher Kyba (@skyglowberlin) March 8, 2017

Because of this, the cloudy night sky can be hundreds of times brighter than a starlit sky far from cities. https://t.co/zl7LIIh1yT

— Christopher Kyba (@skyglowberlin) March 8, 2017

Before we had artificial light, clouds made the sky darker, just like they do in daytime.

— Christopher Kyba (@skyglowberlin) March 8, 2017

The amount of light on an overcast night is astounding. In my smallish German town that's not brightly lit, I can read books by it.

— Christopher Kyba (@skyglowberlin) March 8, 2017

Predators can use the extra light to hunt, prey are way more exposed when trying to forage or mate.

— Christopher Kyba (@skyglowberlin) March 8, 2017

IF skyglow has an ecological effect it will be most dramatic on overcast nights. https://t.co/1kE5Or5JE8

Why "IF"? We don't know?

— Christopher Kyba (@skyglowberlin) March 8, 2017

For example, we know that there are all kinds of behavioral changes near lights. But do these result in ecological changes?

— Christopher Kyba (@skyglowberlin) March 8, 2017

Even that's hard, because you must track individuals over several years. Thankfully, there are some experiments now: https://t.co/GtrlryQ269

— Christopher Kyba (@skyglowberlin) March 8, 2017

We are currently performing the first-ever controlled experiment on ecological impact of skyglow: https://t.co/6U0K2yG3bc pic.twitter.com/oCJWEeedAb

— Christopher Kyba (@skyglowberlin) March 8, 2017

@skyglowberlin Incidentally, phys/eng @AndreasJechow designed and led the implementation of the system, you probably want to follow him.

— Christopher Kyba (@skyglowberlin) March 8, 2017

We've documented how a large fraction of the Earth's land surface is affected by skyglow on clear nights: https://t.co/Ta0Rqb4MeC

— Christopher Kyba (@skyglowberlin) March 8, 2017

So that's the end of the introduction. Now we come to how we measure skyglow.

— Christopher Kyba (@skyglowberlin) March 8, 2017

Pretty much everyone should be familiar with the famous satellite images of Earth at night. pic.twitter.com/l0Yasi7chg

— Christopher Kyba (@skyglowberlin) March 8, 2017

First: the satellite sees light heading up into space, not down to the ground. That's kind of an important difference...

— Christopher Kyba (@skyglowberlin) March 8, 2017

This is because the distance to the top of the atmosphere is way larger if you travel horizontally than if you head straight upward.

— Christopher Kyba (@skyglowberlin) March 8, 2017

This is huge, because a change in lamp design (for example to LED) can nearly completely eliminate horizontal light.

— Christopher Kyba (@skyglowberlin) March 8, 2017

But ONLY if you buy good LEDs & install correctly. There are plenty of crappy LEDs that still direct light upwards, and many are glaring. pic.twitter.com/vqt37z0msA

— Christopher Kyba (@skyglowberlin) March 8, 2017

The only satellite that observes night light globally (@NASANPP ) is COMPLETELY BLIND to blue light (<500 nm).

— Christopher Kyba (@skyglowberlin) March 8, 2017

That's a disaster for two reasons:
1) "White" LEDs have a lot of blue
2) The clear sky scatters blue light the best (i.e. the sky is blue) pic.twitter.com/8yQH019Mu1

— Christopher Kyba (@skyglowberlin) March 8, 2017

So we need to measure skyglow from the ground. Lots of scientists are doing this. The most common device is the "Sky Quality Meter" pic.twitter.com/irDoaag8UJ

— Christopher Kyba (@skyglowberlin) March 8, 2017

The SQM has spectral problems as well, particularly for LED switch as recently detailed by @pmisson et al.: https://t.co/0luP5fRQWV

— Christopher Kyba (@skyglowberlin) March 8, 2017

One problem is the color switch with LEDs, but let's leave that aside (eventually color stabilizes, and you can track changes again).

— Christopher Kyba (@skyglowberlin) March 8, 2017

Imagine if every single lamp in Berlin were changed (or turned off). I'd notice almost no difference in nearby Potsdam (~20 km distant)...

— Christopher Kyba (@skyglowberlin) March 8, 2017

So while records from professionally maintained stations are great, they only tell us about changes in a handful of places (say ~200).

— Christopher Kyba (@skyglowberlin) March 8, 2017

If we want to understand how skyglow is changing GLOBALLY, we need globally distributed observations. Here's where #citizenscience comes in.

— Christopher Kyba (@skyglowberlin) March 8, 2017

You don't need expensive instruments to take part, you just need eyes and an Internet connection to take part in @GLOBEatNight.

— Christopher Kyba (@skyglowberlin) March 8, 2017

.@GLOBEatNight works by getting people to say how many stars they can see, compared to several star charts. pic.twitter.com/st34VYvZzY

— Christopher Kyba (@skyglowberlin) March 8, 2017

Tens of thousands of people have taken part, but unfortunately participation is dropping right as we are switching globally to LEDs! pic.twitter.com/ffGe8dG2kP

— Christopher Kyba (@skyglowberlin) March 8, 2017

Each given individual @GLOBEatNight observation isn't very accurate. But the data are highly accurate in aggregate: https://t.co/g7ge6h9pAo pic.twitter.com/Knk2hRT2RD

— Christopher Kyba (@skyglowberlin) March 8, 2017

1) Make cities track #lightpollution as part of environmental monitoring.
2) Massive global monitoring by citizen scientists.

— Christopher Kyba (@skyglowberlin) March 8, 2017

It's also possible to improve accuracy of visual observations by using the Loss of the Night app, but only in cities https://t.co/kt14p5r0sf pic.twitter.com/QI0OjXP2Ap

— Christopher Kyba (@skyglowberlin) March 8, 2017

Thank you editors of Twitter for reading my submission. I hope it will be accepted for publication

(RT #FirstTweet https://t.co/hnEcFSCJHg)

— Christopher Kyba (@skyglowberlin) March 8, 2017