Friday, May 27, 2016

Skyglow surveys with an SQM and the Loss of the Night app

I was just looking through the Loss of the Night app data, and noticed that a project participant used the app and an SQM to do a skyglow survey of the island of Öland, Sweden:

Öland skyglow survey is licensed under a
Creative Commons Attribution 4.0 International License.
Link to the interactive map at

I reached out to Jörgen Tannerstedt, in order to get the story behind the map. Here's what he told me:

The story behind the measurements is that we last year started a project called "Dark sky Öland" in the local astronomical society on the Island of Öland, Grönhögens Astronomiska Förening (GAF). We are a rather small astronomical society, with fewer than 30 members, but we like our island and the darkness that we've got, and we want to protect it for the future and make others aware of it. There are also some plans/thoughts of applying to IDA and try to make some part of the island a dark sky park or reserve. The southern part of Öland is a world heritage site, and perhaps one could try to make that to a light protected area as well.

"Night over the lake" is copyright Jörgen Tannerstedt.
Used with permission.

As a first step in this project we bought a SQM-LU meter to start measuring the sky brightness all over the island. I guess I´m the most active member in our society, so I got the meter in my hands and have brought it with me most of the time when I´m out shooting. I take mostly astroscape images from the island, some of them can be seen here.
I recently got myself a telescope, and had it just set up before we lost the dark nights here up in the north. So now we just want the summer to end and get the darkness back :P August 10th is the first night with astronomical darkness again after the summer break for the island.
"Stargazing" is copyright Jörgen Tannerstedt.
Used with permission.

So far I have measured over a hundred different locations on the island, several locations multiple times and I will continue doing this during the autumn. There are still several good locations left, and I also want to measure in and close to villages to see how much influence they have, and how much light is spread to the nearby surrounding.

It´s rather recent that I discovered the Loss of the Night app, and it has made things so much easier for documenting the measurements. I really like the ease of use, and that the observations are automatically GPS tagged.

Our measurements will be used to evaluate how good and dark the sky is, and serve as a "before" value to see if it gets better or worse in the future. For example, the area near the bridge to the mainland is under heavy construction, and a lot of new houses are being built with road and street lights etc.

The measurements are also going to be used in a guidebook that another member, Lars Magnusson, is working on. In the guidebook, we will include a lot of good locations for astronomers that want to come to the island and experience our dark skies. We will also include information about the different locations, availability, public toilets, photos etc. Hopefully will we have a first version ready this autumn

When shooting from the southern cape of the island, the camera can easily pick up light from cities the other side of the sea, like Gdansk/Gdynia area in Poland. For example, in this picture the light pollution out to the right under the central parts of the Milky Way are from Gdansk/Gdynia, about 250 km away.

If anyone would like to come and visit the island we have the astronomical darkness back again august 10th, and then later in the beginning of september with the new moon, we have our yearly star party "Sagittarius". It's a rater small party with some spontaneous lectures during the daytime and most often a geological excursion and then stargazing all night :D It's always nice to meet others with the same interest. During summertime, there are a lot of tourists here, from Germany, the Netherlands, and Belgium. We've even got a hotel here that is named "Drei Jahreszeiten*". The winter is not that fun, and pretty windy here, so I understand they skipped that season :D But so far I haven't heard anything about any astrotourists.

* "Three seasons"

My hat goes off to Jörgen and the other members of GAF for documenting, sharing, and especially working to preserve your natural starry skies on the island of Öland! Hopefully your book will lead to a few extra astrotourists to fill up the Drei Jahreszeiten hotel!

While it's nowhere near as organized as what GAF is doing, I have taken advantage of my trips to the state of Mecklenburg-Vorpommern in Germany with some similar goals in mind. I also hope this area will someday be home to one or more recognized International Dark Sky Places, where the communities have recognized the value of the night sky as a natural resource, and agreed to work together to protect it. Here's my map:

Skyglow survey MVP is licensed under a
Creative Commons Attribution 4.0 International License.
Link to the interactive map at

If you have an SQM, this method of surveying is a wonderful way to contribute to environmental monitoring of Earth's night! The data are shared with everyone around the world, and they contribute to a permanent archive of the skyglow conditions at the site. If you are planning on founding an International Dark Sky Park or Reserve, this allows you to document the conditions at your site transparently, and future visitors will be able to verify your results and contribute to monitoring changes in the sky condition.

Please note that the best way to do an SQM measurement is to average the result of 4 measurements with your body oriented in the four different compass directions. This is the recommendation from the Loss of the Night Network, and we have found that it considerably reduces the size of the uncertainty compared to taking just a single measurement. Here is the full text of the recommendation from the LoNNe report:

Recommendation #1: When making observations with a handheld SQM-L, you should average the result of four observations, rotating your body after each observation to a different compass direction. If the SQM-L is being affected by stray light, this may minimize or reveal the effect. If the four observations are not self-consistent (maximum range about 0.2 magSQM/arcsec2), then it is probably not a good location, and the data should not be recorded. This technique has been suggested by Andreas Hänel in the past, and we advise all handheld SQM-L users to adopt it.

Wednesday, May 25, 2016

Good Morning Twitter!

Together with Tatjana Scheffler, I recently published a paper where we looked at what time German Twitter users wake up, and how it varies throughout the year. Here's a really short explanation.

What we did

Dr. Scheffler collected and saved (nearly) all the German language tweets for an entire year. She then selected all the tweets that included the German phrase for "good morning" (Guten Morgen). We then analyzed the data to find what time each morning the phrase really starts to take off, and called that the "onset of twitter activity" (i.e. what time people woke up).

What we found

The data can be best explained visually. Here is a plot of what time the sun rises (in Frankfurt) throughout the year. Winter is near the middle, and the "fall back" and "spring ahead" of Daylight Savings Time are shown as dashed lines. We don't change the clocks on this plot, to make it easier to see how wake times relate to the sun.

Now here's what wake times look like on weekdays:

Throughout the year, the typical* wake time on a weekday is around 5:50 am (in local time). You can see that there are a few weekdays that look very different from typical. Those are holidays, and the bunch in the middle are the days between Christmas and New Years.

Now here's what it looks like on Saturdays:

And here's Sundays:

You can see that during the late fall winter, and early spring, the wake up times on weekends are closely related to the time that the sun comes up. But then Daylight Savings Time comes and the relationships break down. Here's what it looks like with all the data together:

The gap between the blue compared to the black and red lines shows you how badly people are punishing themselves by using an alarm clock. About 80% of people in Europe use alarm clocks, which means that they aren't getting a full night's sleep. But what can we do about it?

Take a look at the difference between the blue and red lines. You can see that at the end of March, they're almost reaching each other. If they were to touch, it would mean that millions of people would manage to wake up fully rested without needing an alarm clock.

The plot shows that Daylight Savings Time lasts too long. If it started later in the spring and ended earlier in the summer (or if it was eliminated altogether), millions more people would get a good nights sleep. We would be healthier, feel better, be less likely to be involved in car crashes, and our entire society would be more productive. High school and university students would benefit in particular, because they need to sleep in the latest. Schools would have fewer disciplinary problems, students would fall asleep less often in class, and because they are alert, they would learn more.

If you'd like to read our full paper, it's freely available online. If you'd like to have a laugh and hear more about how terrible Daylight Savings Time is, here's John Oliver asking how it's still a thing:

* This might seem a bit early, and it is. It's related to the method we chose to select a single time. Long story short, some people wake up earlier than this, most people wake up later, but the time shown here is the most stable measure for start of twitter activity.

Wednesday, May 18, 2016

A tale of two lamps

This photo is taken from the bridge over the Warschauer Strasse S Bahn station in Berlin (daytime street view). Good lamps aren't visible from the side or above.

Lamp comparison by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Unfortunately most lamps aren't good lamps, as you can see in the original:

Warschauer Strasse railway at night by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

It's pretty likely that the brightly lit area under the "good" lamps is overlit, because it's so much brighter than the other lit areas. So actually these lamps aren't really ideal either. But it demonstrates the point that there is no need to waste energy and destroy the night by shining light in directions that aren't at all useful.

Monday, May 16, 2016

Night lights and prosperity don't always go hand in hand

North Korea is famously dark compared to South Korea and China at night, and images like the one below are often used to demonstrate the consequences of its "unenlightened" policies.

Photo ISS043-E-247811 from the International Space Station ISS.
See more like this at Cities at Night.

I certainly wouldn't want to live in North Korea, but is it an absolute truth that bright lights indicate prosperity, and lack of bright lights poverty and backwardness? The border between Germany, Belgium, and The Netherlands would suggest otherwise:

The border of The Netherlands, Belgium, and Germany at night.
Image from an International Astronomical Union press release.

The area of Germany shown in the photo is part of the Ruhrgebiet, home to 8.5 million people and one of the most industrialized areas in Europe. Nevertheless, the comparison of Germany to Belgium and The Netherlands is nearly as visually striking as that between North and South Korea. This is at least partly due to German lighting policy: Germany rarely lights its Autobahns (highways), and cities and towns are conservatively lit, often intentionally not following the European (DIN) norms for street lighting.

Last year we published a paper that examined the differences in lighting between cities and towns in the USA and Germany. American towns of 10,000 emit on average three times more light per capita than German towns, and cities of 100,000 emit more than five times more light per capita.

Total light emission from cities in Germany and the USA compared to community population.
Figure 5 from "High-Resolution Imagery of Earth at Night: New Sources, Opportunities and Challenges".

Germany uses far less light than its neighbors and the USA. Despite this, it is a prosperous country that is highly visited by tourists. It has low crime rates (the burglary rate is only 1/3 of that in the brightly lit Netherlands and just over half that of Belgium) and low rates of death due to traffic (about 1/3 less per 1 billion vehicle kilometers than USA or Belgium).

So if bright lights aren't needed to attract tourists, reduce crime, or make driving safer, then why do so many cities have such bright lights? Now that's a $100 billion question.

Note: Thanks to Alejandro Sanchez de Miguel for sharing the two ISS images with me.

Update: If you liked this post and want to learn more, check out this blog's "view from your app" photo series, that often highlights how good lighting is about more than how bright lights are. Some other blog highlights are about what a single floodlight can do to a natural area, the promise and peril of LED lighting, and citizens push back on LED lighting.

Tuesday, May 10, 2016

Look what happened when Circle K improved its canopy lighting

Mike Weasner recently took some photos of a change in lighting at a Circle K gas station near Arizona's Oracle State Park, which is designated an International Dark Sky Park by the IDA. By installing the lights within the canopy rather than below it, the gas station kept its pumps well lit while eliminating the glare of the old lamps. The new design also greatly reduces the artificial skyglow produced by the site, because light emitted towards the horizon is the most likely to be scattered back to Earth before it reaches space, and because Circle K chose a warm looking LED with 3000 K instead of an LED with a higher fraction of blue light.

Improved Circle K lighting by Mike Weasner is licensed under
a Creative Commons Attribution 4.0 International License.

Local businesses and Chambers of Commerce are usually very supportive of efforts to create dark sky parks, because they tend to bring in a lot of additional visitors into the area. As you can see from Mike's photos, being near a Dark Sky Place doesn't mean giving up artificial light, it just means using it more wisely.

Thursday, May 5, 2016

Sometimes lamps make it hard to see

When you ask the question "why do we have outdoor lighting" the reason most people come up with first is for safety". But it often happens that lamps actually make vision worse than it would be if it wasn't there, as we've seen on the blog before. Lighting can be especially tricky near staircases.

I'm currently in Montsec, Spain, for the 4th LoNNe Intercomparison Campaign. We are staying in a wonderful hotel in a region that is brightly lit with stars. On the days that the hotel has kept the lamps off for us, this staircase has been easy to climb with adapted eyes under starlight:

But on the first night we were here, it looked like this in the night:

The light flashed through the stairs, and made it very difficult to see. The culprit was this old-timey style lamp mounted near a doorway below:

If the lamp was better shielded so that it didn't shine sideways (and upwards), the guests at the hotel would have a safer and easier trip up to their rooms at night.

Creative Commons License
The three photos above by Christopher Kyba are licensed under a Creative Commons Attribution 4.0 International License.