Lighting in Sherbrooke, Quebéc

The Third International Conference on Artificial Light at Night just wrapped up today in Sherbrooke, Quebéc. Walking through the city this evening, I took a few photos of some street lights that caught my eye. Sherbrooke has made a major commitment to minimizing the city's effect on the nighttime environment, and one of the ways they do this is by replacing older lamps with newer fixtures that don't send light up into the environment. You can see this really well in the photo below, where the fixtures aren't visible from above, but by the reflection in the water you can see how bright they are:

Full cutoff lights reflecting from a river by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Of course, near a waterway the ideal light shines only on the path and not into the water... But I think it's a great photo for demonstrating how full cutoff lights work. In most cities, there would be two bright spots - one from the lamp and the second from the reflection.

The same lamps were on the bridge I was crossing over the river when I took the photo, and I was impressed that in addition to not producing any upward directed light, they also have very little glare. Compare the two photos below - which street would you rather drive on?

Low glare streetlamps by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Glaring streetlamps by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

In a few weeks, the Artificial Light at Night conference will start to fill up with pdfs and videos of the presentations. There will even be a video of me, talking about the Loss of the Night app!

Star trails over Milow, Germany

Blog reader JC Cabrejas passed on this image that he took while near the International Dark-Sky Reserve Westhavelland.

Polaris by JC Cabrejas is licensed under
a Creative Commons Attribution 4.0 International License.

You can read about how the image was made on his blog. I recently posted some all-sky images from the same region, including one time-lapse showing a set of twelve street lamps turning on and brightening the nearby environment.

LED color temperature

A new contact that works on lighting castles sent me the photo below. It compares the light provided by an incandescent lamp (left) to the "warmest" white LED that their group could find (right).

Image used with the permission of the
Prussian Palaces and Gardens Foundation Berlin-Brandenburg

The problem with the LEDs, from her perspective, is that the blue light component is too large, and the colors of the objects in the castles are not properly represented. LEDs can be adjusted to provide nearly any color that's desired, but their "luminous efficiency" is often worse than a very cold, blue-white LED. This is the main reason why so many LED street lights glare with such an ugly, cold light. But it doesn't have to be this way!

An overly narrow focus on the luminous efficiency of lamps misses the point about saving energy. For example, regardless of how high the luminous efficiency of the lamp in this photo is, it's not being used in an efficient and sustainable way:

Light on during the day by Christopher Kyba is licensed under
a Creative Commons Attribution 4.0 International License.

Some colleagues and I wrote an article about how a more common sense view of the "efficiency" of a lamp its energy use per year, not the efficiency with which it converts electricity into light causes a human visual response.

While making a decision about how to light a space, energy consumption is a very important consideration, but the people who will use the light should never be taken out of the equation! In Davis, California, the city decided to let citizens choose which lamps they liked after residents  had protested the installation 4,000 K LED streetlights. The public ended up choosing warmer 2,700 K lamps. In addition to being more liked (or at least more tolerated), warmer LED lamps also have a smaller impact on the night sky than the most efficient white LEDs.


When the Nobel prize was announced last year, I wrote:

"It's possible to imagine a future in which driverless cars run without headlamps ... pedestrian and cyclist lights provide more uniform lighting at greatly reduced light levels, and the sky above even large cities once again glitters with thousands of stars."

For that to come to pass, the focus of sustainable lighting is going to have to shift beyond luminous efficiency, and keep the users of light in the center of focus.

The night sky over Westhavelland, Germany

A few weeks ago I was in Sternenpark Westhavelland (International Dark-Sky Reserve Westhavelland) to try to measure the degree to which individual streetlights affect the night sky in a pristine area. The lamps are part of a biological and ecological field experiment of the Verlust der Nacht (Loss of the Night) project, funded by the German Ministry of Education and Research (BMBF).

Together with a colleague, we walked different distances from the lamps and then remotely the lights them off and on. In addition to measurements with a continuous logger, I took a few all-sky images. This one is from the middle of the field when the lights were off:

Verlust der Nacht field at night by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

You can download the full resolution version here. The sky is blue because it is lit by lunar twilight. The glow at the right (East) is a combination of the moon and the city of Berlin. The glow at top left (southeast) is the nearby town of Rathenow.

The next photo shows the view a few hundred meters from the field when the lights are turned on (the field is the bright glow at right):

Verlust der Nacht field lit at night by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Finally, this animation shows how the whole environment near the field changes as the lights turn on:

Verlust der Nacht field turning on by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

I think the lighting up of the nearby tree and grass is the most dramatic - just think of what a complete difference this is for the insects and birds that live there! Here's a higher resolution version.

UPDATE Nov 23, 2015: We have published a paper describing the field site and a few of the first experimental results. You can read about it for free at the journal Sustainability.

Sign up for our new monthly newsletter

We're starting a newsletter to remind project participants each month when the moon phase allows Loss of the Night app measurements to be taken. In the monthly mail, we'll also occasionally share news, such as announcements of new versions or project milestones that we've passed. You can sign up for the newsletter here, or just fill in the form below.

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The Loss of the Night app is two years old!

April 22 is the second anniversary of the Loss of the Night app! Since that time, tens of thousands of people have installed the app on their phone, and thousands of those people have used the app to make at least one observation of the night sky.

Here are some statistics from the first two years (for data up to April 18):

20,170 individual observations have been submitted from 9,825 unique devices from around the world (see map below). This number includes "demo mode" cases when people are just testing the app, and observations with clouds and sunlight or moonlight. Most devices have only ever observed once, but over 100 people have submitted ten or more observations.

App observations up to April 18. Black points are all observations,
red points are observations with no twilight, moonlight, or clouds
and at least 7 stars observed.

In the first few months, only about 10% of the submitted observations were suitable for analysis (no clouds, moonlight, twilight, and at least seven stars observed). This fraction has steadily increased over time, and is now close to 30% of the observations submitted. The number of good observations per month is also climbing, but slowly. The more participants we have, the quicker we'll be able to measure the average change in sky brightness worldwide, so tell your friends about the app!

Citizen scientists have searched for a total of 30,323 stars (under nighttime conditions). The star most commonly searched for so far is Capella (694 times), followed by Vega (593x) and Altair (554x). Since the new version was released, many of you are now submitting more than the minimum seven stars. We really appreciate it, because observing more stars leads to a more precise result.

The mean time to observe a star is 34 seconds, but the most frequently occurring time needed to make a decision is 11-15 seconds. Your data help us understand which are the "best" stars for us to ask you to look for. I hope that we will do one last update to the app's "star selection algorithm" in the next year or two, so the more stars you observe, the more you'll improve the app.

In addition to the naked eye observations which are the main purpose of the app, citizen scientists have also used the app to submitt 239 observations taken with Sky Quality Meters under nighttime conditions. Of these, 188 of which were taken with with no cloud cover.

Thank you to everyone who has taken part in this project to measure how Earth's night sky is changing. It wouldn't be possible without you! The next moon-free observing period starts around May 7. If you don't yet have the app, here are the links for downloading it for Android and iOS.

Minor bug report

Users at high latitudes (like Germany) may have noticed today that the app crashed after it acquired a GPS signal. The bug was caused by an expectation that the "next good time" to observe should be within 30 days, but during the summer at high latitudes the twilight extends past the time we thought people would be interested in observing.

The bug has been fixed, and in the next few hours the update should be available in the Play and App stores. We didn't notice the bug in testing, because our testing took place after the midsummer twilight was over last year.

Observers in Germany that are willing to stay up past midnight are able to observe from about May 7-18. If you live at a lower latitude, the bug probably didn't affect your phone.