Monday, November 14, 2016

Four super activities for tonight's "Supermoon"

Tonight is the night of the "supermoon", meaning the moon happens to be close to it's "perigee" (the closest it gets to the Earth) at the same time as it is full. As it happens, tonight's supermoon is an especially good match between moment of fullness and perigee: the last time the full moon was this close to Earth was in 1948, and the next time it will be this close is in 2034.

When the moon is closer, it appears ever-so-slightly larger than normal. This makes some people roll their eyes at all the attention, but I think anything that gets people out to experience the night should be celebrated! With that in mind, here are four things you can do to celebrate tonight's moon (the first 3 are great for kids):

1) Watch the moonrise

When the moon is near the horizon, an optical illusion makes it look bigger than usual. This makes every moonrise special, but the experience is most exciting when the moon is big and full. One fun activity, especially for kids, is to bend over and look at the moon upside down through your legs. For many people, this destroys the illusion, so you can switch back and forth between having a big and small moon.

You can look up the moonrise time at your location here. For observers at high Northern latitudes where night is already falling, the moon will appear quite red, because the blue light is scattered by the atmosphere.

2) See how well you can see with only ~0.2 lux.

Once the moon has risen high in the sky a few hours later in the evening, go out into an area that's as free as possible from artificial light. A big (unlit) park or sports field will work in a city, and an open field works best in the country, but a back yard will do in a pinch. You'll probably find that you can see better than you can on a typical urban street, even though lit patches under streetlights are usually 100-500 times brighter than full moonlight. The reason for this is that the moon lights the landscape uniformly, and most importantly without glare. A recent paper argues that even older pedestrians need only 1 lux to avoid stumbling, and this experience shows to what extent we could reduce energy use and light pollution if we improved urban lighting to make it more uniform.

3) Test whether you can see color and read text under full moonlight

Before you head out the the park, grab a colorful magazine and take it with you. Many people can read text and see colors in full moonlight, but a lot of people incorrectly believe that the moon isn't bright enough. Who in your family can read the easiest? Can you tell what all colors are, or just some of them? Speaking of colors, use something to block out the moon and look at the sky around it. Many people experience the sky as shining blue near the moon.

4) Take moonlit landscape photos

If you have a camera with a programmable shutter speed, you can take absolutely wild photos by moonlight. All you need is a tripod or stable surface to rest your camera on (here's a moon landscape photography tutorial in case you want to get really serious). Once the moon is high up in the sky, take a photo of the landscape, and you'll end up with a fully lit scene, but with stars shining in the blue sky!

An example of one of my favorite moonlit photos is below (although this was far from full moon, and the exposure was kept short because the moon was in the photo, so the sky doesn't appear blue):

Moonrise over Nationalpark Müritz by Alejandro Sánchez de Miguel is licensed
under the Creative Commons Attribution 3.0 Unported License.

If it's cloudy or raining where you are, you could try for two other phenomena. One of the hardest things there is to photograph is a moonbow: a rainbow lit by moonlight:

Moonbow, Kula, Hawaii by Arne-kaiser is licensed
under the Creative Commons Attribution-Share Alike 4.0 International license.

Finally, if it's overcast where you are, I'm still waiting for someone to answer my challenge of taking a landscape photo on an overcast night in an area without significant light pollution. Maybe tonight will be the night!

Thursday, September 8, 2016

Second community App experiment!

It's high time for another community experiment using the Loss of the Night app!

Last year we examined how stars come out during twilight, which is also useful for understanding the different times at which stars come out for people. This time, we're going to try seeing how much variation there is in an individual observation due to the random set of stars selected by the app.

To take part, you should make an app observation with 8 stars (quit once you've reached 8 stars). Then, start the app again, and do a second 8 star observation. To make sure that we don't see changes due to city lights going off, both observations should be completed within a single 30 minute period.

Both times you run the app it will probably start with the same first and second stars, but the rest of the stars are likely to be different. Since you are the same observer looking at the same sky, your data will help us understand how much of the variation in observations is due to the design of the app itself, rather than differences in sky brightness.

You can do this on as many evenings as you want to from September 22 until about October 6. I'll present the results in an app newsletter email and here on the blog towards the end of year.

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.

Wednesday, April 27, 2016

Model of exponential growth in skyglow at one location

Andrej Mohar produced a video modeling skyglow changes from 1950-2040 at Matajur mountain on the border of Slovenia and Italy:

The simulation is based on a calibrated all-sky image taken at the site, with an estimate of 5% annual growth in skyglow (which is a pretty reasonable assumption for the later half of the 20th century). But there's no reason that skyglow must continue growing at such a rate! If we get smart about how, where, and when we light, we could recover the starry skies that many of us remember from our childhood.

Wednesday, March 16, 2016

VdN App and MySkyAtNight wishlist

How can we improve the app?

Your feedback helps us improve the app. We don't currently have funding for further development, but hopefully that will change in the future, and we can do one final change to the method, and then fix it for a long period. If you have more suggestions for how to improve the app, please let me know in the comments.

Things to change/improve in a future version of the app

Star search

  • Further improve star selection based on app data (preferentially use easier stars)
  • Make more use of "pointing stars"
  • Allow search to start with Venus or Jupiter
  • Allow the user to change the sensor settings (speed and/or damping)
  • When screen is frozen, allow navigation by sliding finger 
  • Option in settings to not lock screen when star is found
  • Shaking the phone unlocks the locked circle (goes back to arrow) 
  • Try to work out that the user is standing on a balcony, and don't suggest stars in that direction 
  • Allow the user to adjust the number of stars displayed on the screen to match a given skyglow level? (we don't want to do this, as this could potentially cause biased observations)


  • Add reminder: "never use the app alone" at start up
  • Improve clarity that data will be transferred by requiring opt-in to send the data once the observation is finished, and follow up with a second reminder that the location will be made public, require second opt-in for data to be sent
  • Figure out what causes the occasional crash on startup
  • Strategies for classifying areas with NELM>5
  • Interface to allow advanced users to submit what their estimate of the limiting magnitude is
  • New "constellation mode". Highlights a single constellation, and the user has to click on a star to declare it visible (turns from dot to star) and click a second time to declare it invisible (turns from star to empty circle or x), click third time for "just at visible limit"
    •  Or extend this mode to cover several hundred stars over the whole sky, and the observer can just pick which ones she wants to label?
  • Manual way to calibrate the compass to remove azimuth error 
    • Add a compass-free option in "settings" menu for places with weird magnetic fields
  • Investigate behavior of auto brightness on Android (does it turn to full on app startup for some phones?)
  • Allow "SQM only" install for phones without gyroscope/compass 
  • Add button to "send again" on the data page (for data points that don't get sent - and return a debugging message if it can't be sent?)


  • Badges - you've observed 7 stars, you've repeated an observation at the same location ~1 year later, you've done 10 observations, 5 times in a single city, 5 locations, etc...
  • Guide users to locations that we particularly need measurements (e.g. repeat measurements from previous years).
  • Incorporate SciStarter API to allow participants to track their contributions across various citizen science projects.
  • Incentivize good data: Have a friendly competition where the best quality and quantity is rewarded (with a visit to the closest telescope and a personal lecture from an astronomer). Reward observations in particularly important locations
  • Welcoming email to new participants
  • Option to have your observation results emailed to you after each session
    • Option to share your observation on social media after the session
  • Add option to user settings that data is visible on the public map. Make the user choose which setting they prefer when they conclude their first observation.

Extra features

  • Check the clock using GPS and warn the user if their phone's clock is off by more than 2 minutes (and then exit app). Prevents records having a false time
  • Allow option of displaying user's location on a map to make sure it is correct
  • A "talking" tutorial that tells you how to find the stars, asks you to turn in different directions, etc.
  • Video tutorial
  • Allow observing below 45 degrees and making maps of the stellar visibility on the full sky dome (expert mode)
  • Find a way to calibrate the compass within the app (on Android, iOS already has this)
  • Incorporate My Sky at Night into the app itself
  • Port to WindowsPhone and Blackberry


  • Start looking for GPS location on app start up, verify again before star search
    • Especially for SQM report, GPS should run in the background while typing value
  • Reduce the size/thickness of the circle during the star search on Android
  • Better messaging in "Not dark enough" menu during high latitude summer 
  • Allow users to add SQM serial number, and SQM-L or SQM
  • Remove names of unused stars & constellations, to make it easier on the translators 

My Sky at Night

  • Allow users to customize font size and color, and background color
  • Minor bug fixes:
    • Duplicate observations
    • Display of transmission instead of acquisition time (e.g. observation 40417) 

Now it's your turn. What other changes should we make to the app?

Wednesday, March 2, 2016

Globe at Night turns 10!

The Globe at Night project turned 10 years old this month! Citizen scientists have contributed tens of thousands of data points over the last 10 years:

Clear-sky moon-free Globe at Night observations, 2006- Feb 2016.
Explore the data yourself at!
In its early years Globe at Night wasn't a year-round campaign, so for time series analyses March is the most important month for new Globe at Night observations. So if you have clear skies between now and March 10, take a moment to look for Orion, and let Globe at Night know how many stars you can see by filling out this form (available in 28 languages).

Wednesday, February 24, 2016

The new version of the Android app is out

The Android version of the Loss of the Night app has been updated (new version is 2.1.5). The main changes with this update were to target the boundary between averted vision and not visible (it was incorrectly set to target the boundary between visible and averted in the last version), and to deal with the (rare) problem that some phones sometimes reported incorrect GPS positions.

The solution we introduced to solve the GPS problem may unfortunately prevent some phones from using the smoother gyroscope function that was introduced with the second version of the app. If you notice that the display of the stars seems jittery, try immediately quitting the star search and starting it again. If that doesn't work, please contact me to let me know what model of phone and which version of Android you are using. While we do not currently have funding to do further development, your input could help us figure it out more quickly in the case we do find additional funding.

Monday, January 11, 2016

Do you want to translate the Loss of the Night app into your language?

I currently have offers to translate the Loss of the Night citizen science app into 3 additional languages. When I have at least 5 additional languages, I can arrange a new release. Please let me know if you are interested in helping by volunteering to translating two XML files and the text for the play and app stores into your native language. You can expect the job to take about four hours of translation time, plus about 20 minutes verifying that the translation works correctly in the app.

The app is already translated into: Arabic, Catalan, Chinese, Czech, French, German, Hebrew, Italian, Japanese, Polish, Romanian, Slovak, Spanish, and Turkish. If you are interested volunteering a new translation, please send an email to Christopher Kyba.

Wednesday, January 6, 2016

Top 5 posts of 2015

Here's the top five most read posts from this blog last year:

1) A brief introduction to the project - Hurrah for brevity!

2) The Globe at Night revisit project - Help us re-sample locations to see how the sky has changed.

3) Effect of a single floodlamp in a natural area - If you haven't seen the photo yet, check it out now!

4) Citizens push back on LED lighting - Want good lights? Talk to city hall!

5) Amazing new photos from the International Space Station - High-res photos of cities at night.

Thanks for reading! The current moon-free period runs until about the 10th. Help us track how the sky brightness were you live is changing with our app, Globe at Night, or the Dark Sky Meter app! Once you've made an observation, you can view it at My Sky at Night.