Tuesday, December 9, 2014

Have astronauts photographed your city at night?

Back in July, I blogged about a new portal that helps you find photos of cities at night, and three related citizen science projects. I have some astounding news about the project that I just needed to share!

Citizen scientists have completed the initial classification of over 130,000 images in the Dark Skies of ISS project. This projects sorts images taken at night on the international space station as to whether the picture contains either stars, cities, the astronauts, etc, and how sharp the image is. To avoid errors, each image was categorized by multiple participants, so that's probably over half a million classifications in less than half a year!

In the Lost at Night project, citizens apply their lay knowledge of local and international geography to identify which cities are in specific photographs. Every photo is again categorized multiple times, and this has resulted in the discovery of almost 2,500 images of cities that researchers like me didn't know existed. Images from cities like San Jose (shown below), and also from places less well known to Americans and Europeans, like Chennai, Inda, or Da Nang, Vietnam.

San Jose from the International Space Station.
High resolution image available from NASA.

The citiesatnight team has released a preliminary set of these photos within a Google interface so that you can easily check if your city has been photographed. Please bear in mind that this is not a final product. If you find a city that has been misclassified, they would appreciate it if you would report it to them. Believe it or not, that link contains only the cities classified by citizen scientists. The Atlas of images put together by professional scientists and enthusiasts is actually smaller in terms of number of images, and I explained the best way to use it in July.

Finally, the citiesatnight team has also released seven examples of images that were georeferenced by volunteers. In the Night Cities project, participants match locations on the image with locations on Google Maps, allowing the photos to be overlaid on top of a map. A total of 128 cities have already been georeferenced.

Manhattan at night, georeferenced by citizen scientists at citiesatnight.org

The citiesatnight project has been an astonishing citizen science success story. The project was put together almost entirely through volunteer time, as far as I know it hasn't received any government financing. The International Dark-Sky Association recognized its leader Alejandro Sanchez de Miguel with an award this fall. If you know of other ways in which the project could be recognized, please nominate it!

Note to journalists and researchers: citiesatnight asks that you cite this paper if you use the images in your work.

Full disclosure: Alejandro is a close friend of mine. I played a limited role in the project, mainly by providing some minor advice and lots of encouragement.

Monday, December 8, 2014

Greenhouses at night

Last week I posted some photos showing examples of trees that seemed to be affected by the light from nearby street lamps. There hasn't been much research into what effect (if any) street light has on trees. But when it comes to higher light levels, we do know that plants respond to the light, and use it to grow.

Some greenhouses use artificial light to extend the growing time of plants beyond what is possible with local sunlight. When greenhouses don't bother to capture and redirect scattered light back towards the plants, this can have a really profound effect on the night sky. The image below was taken by my Dutch colleague Kamiel Spoelstra:

Skyglow from greenhouse by Kamiel Spoelstra is licensed under
a Creative Commons Attribution 4.0 International License.

Of the places where accurate measurements of sky brightness have been reported, the brightest skies I know of are near greenhouses in the Netherlands. When you look at satellite images of the Earth at night from the new VIIRS DNB instrument, greenhouses are "blindingly" obvious, because they are tens or even hundreds of times brighter than city centers. This is part of the reason the Netherlands appears so bright - it has a lot of greenhouses!

Northwestern Europe at night by VIIRS

My colleague Florian Tornow took the next two photos from a window on a recent flight to the Netherlands. The first shows a large area of greenhouses:

Greenhouse complex by Florian Tornow is licensed under
a Creative Commons Attribution 4.0 International License.

The second shows how bright they can be compared to the surroundings:

Lit greenhouses at night by Florian Tornow is licensed under
a Creative Commons Attribution 4.0 International License.

In some areas, greenhouse lights only turn on after midnight, because the glow from the greenhouses disturbs the nearby residents. I have heard that newly built greenhouses in the Netherlands are required to keep their artificial light in-house. With better design, instead of emitting light into the atmosphere the light can be redirected towards the plants, saving energy and reducing the impact on the nearby nighttime environment.

Update (December 10): After seeing this post, @RICE_MM shared the photo below on twitter, which was produced by Remi Boucher. It shows how a single greenhouse complex near the small town of Anson in Maine produces light roughly comparable to that of the whole city of Sherbrooke, Quebec (population ~150,000). The image also shows the area of the Mont-Mégantic International Dark-Sky Reserve.

Greenhouse and Sherbrooke by Remi Boucher.
Image and Data processing by NOAA's National Geophysical Data Center.

@RICE_MM also shared this post showing the change in the area from 2010 to 2012:

Wednesday, December 3, 2014

Artificial light and trees

Luciano Massetti, a colleague of mine from the Loss of the Night Network, recently took a series of photos in Florence that show trees near street lamps who's leaves still haven't fallen off:

LAN leaves 2 by Luciano Massetti is licensed under
a Creative Commons Attribution 4.0 International License.

LAN leaves 10 by Luciano Massetti is licensed under
a Creative Commons Attribution 4.0 International License.

LAN leaves 15 by Luciano Massetti is licensed under
a Creative Commons Attribution 4.0 International License.

LAN leaves 22 by Luciano Massetti is licensed under
a Creative Commons Attribution 4.0 International License.

LAN leaves 28 by Luciano Massetti is licensed under
a Creative Commons Attribution 4.0 International License.

At this year's Artificial Light at Night conference, Jonathan Bennie of Exeter University's Environmen and Sustainability Institute presented some intriguing data about a potential relationship between artificial light exposure and how early tree buds burst into leaves and how late leaves fall. His work, and related research by my IGB colleague Sibylle Schroer, isn't published yet, but it's starting to look like people's anecdotal observations that trees near street lamps behave differently isn't just a case of confirmation bias, it's a real phenomenon.

At this stage, there's very little information about which tree species are typically affected, or which types of lights have the strongest effect. Dr. Bennie is interested in pursuing this further, so if you've observed trees under lamps that are behaving differently than adjacent unlit trees, and if you are able to tell him the type of tree and type of lamp (e.g. high pressure sodium or LED), he'd like to hear from you. Photos of the effect are also useful, of course! You can find his contact information here.

If you liked this post, you might want to read the next one, which is about artificial light escaping from greenhouses at night. As always, if you have a photo related to artificial light that you'd like to share with the world, please send it to me along with your permission to publish it on the blog under a Creative Commons Attribution 4.0 International License as part of the "view from your app" photo series.

Tuesday, December 2, 2014

This Christmas, help every star shine a bit brighter

December 2 is Giving Tuesday, and the IDA board of directors has pledged to match the first $5,000 donations that come in today. I wanted to take a moment to encourage you to consider making a donation.

The International Dark-Sky Association (IDA) works together with communities, institutions, parks, and lighting designers to improve lighting worldwide. The IDA does this in a number of ways:
  • The IDA helps parks and communities preserve the resource of a natural night sky through its International Dark-Sky places program.
  • The Fixture Seal of Approval program makes it easy for communities to find lights that shine light where it is needed, and not into the sky.
  • In partnership with the Illuminating Engineering Society, the IDA developed a Model Lighting Ordinance that communities can adopt to regulate lighting.
  • Through partnerships with companies like Lowes, the IDA helps homeowners choose lamps that satisfy security needs while minimizing waste light and energy consumption.
  • The IDA honors individuals who have made outstanding contributions to the protection of the night sky.
  • The IDA helps educate everyone about the consequences of poorly designed lighting through education and outreach programs, such as this planetarium show.
The IDA is largely a member-funded organization, and it needs your help to continue this work. The best way for you to help is to become a member, but you can also help out by making a one-time donation. A donation in another person's name is a great stocking stuffer!

Better lighting doesn't only help keep the stars in the sky, it can also improve visibility and is more efficient. That means lower electricity bills for cities (lower taxes!), and reduced need for electricity production in the night (when solar plants can't operate). Bringing back the stars is a win for everyone!



Full disclosure: I am a member of the IDA board of directors. That means I'm literally asking you to take my money today!

Monday, December 1, 2014

Data not yet appearing on GLOBE at Night maps

We haven't yet updated the scripts that process Loss of the Night app data for the new data format that is produced by the new version of the app. Because of this, your observations might not appear on the GLOBE at Night map. You can check if your data was sent on the "User Data" page under "My Measurements". If it says "successfully sent", then we should have your data.

I will try to remember to post when we have new scripts up and running to generate the points for the map. Sorry for the inconvenience!

Tuesday, November 18, 2014

An example of user data with the new version of the app

I've been browsing the incoming Loss of the Night app data, and I wanted to share the details of a recently submitted observation.

One of the things that we changed in the new version of the Loss of the Night app (iOS, Android) was to give users more options to describe what stars look like. The original app had three options: visible, not visible, and unsure. In the new version*, we now ask users to distinguish whether the star is "clearly" or "barely" visible, and added a new option, "visible only with averted vision".

If you've used the app outside, you've probably noticed that sometimes you can't see a star when you look directly at it, but when you look off to the side it appears. This is because the very center of your eye is packed with color sensing cones for vision in daytime, rather than the rods we use to see at night. The cones aren't sensitive enough to see the star, but if you look just off to the side, your eye has enough rods to let you see it.

The plot below shows the observations that project contributor Matt Sidor took using the app on the outscirts of Davis, California a few nights ago. The filled in blue circles are stars that are clearly visible, the black stars are stars that were barely visible, filled in red circles were visible only with averted vision, and empty red circles were stars that were invisible.


Matt did a fantastic job! With 14 stars, he had almost perfect separation between the stars that he could see directly and the stars that he couldn't. The new classifications give us more information than was available in the old version, and should lead to more accurate estimations of the sky brightness.

The other thing the image shows is how the app now focuses much more carefully on stars close to the limiting magnitude. Compare the stars Matt was asked to see with older data from the original app version below:

The older version of the app was much less aggressive about testing stars near the limiting magnitude. We expect that by staying closer to the limit, user observations will be more accurate. When an observer makes a mistake (it happens!), the range over which the app tests grows in response. When you finish your observation, the app will let you know how accurate your measurement was. If you use the app over time, you can see if your accuracy improves as you get more practice!

* I'd like to acknowledge this recent paper by Andrew Crumey as the inspiration for us to move from 3 possible classifications to 5. In case you don't have access, a preprint is also available.

Monday, November 10, 2014

New version of the Loss of the Night app is released!

The updated version of the Loss of the Night app is now available for iOS and Android!


The app lets citizen scientists like you measure how bright the night sky is, by seeing which stars you are able to see. The more faint stars you can see, the more natural your sky is. Your results are then shared with the GLOBE at Night project, and will be used to track how the night sky is changing in response to widespread adoption of LED lights.

What's in the new version?
  • Improved feedback: We fit your data and tell you the estimated naked eye limiting magnitude, approximately how many stars are in your sky, and how consistent your observations were:

  • Smoother behavior: Phones that had problems with an unstable star field should now be fixed.
  • More customization: You can change font sizes and switch the screen brightness between a city/country mode. Pinch zooming will replace the zoom buttons.
  • Better night mode: Removal of gray backgrounds and replacing orange with red in many places.
  • Improved measurement technique: new options to tell us if the star is clearly or barely visible, or if you can only see it with averted vision
  • Better set of stars used: So the app is quicker and easier to use, and more accurate
  • Expanded language support: To Czech, Hebrew, Slovak, and Turkish
  • News about our project: Links to these blog posts on the news page
  • Calculation of next possible observing time: If the moon is up, the app will figure out when the next good (evening) observing time is for your location, and let you put it in your calendar
  • Feedback button: So you can tell us what we should do next! 
  • Faster GPS convergence

Thanks to everyone who gave us feedback on how to improve the app, to the translators, and to everyone who has used the app and provided us with data. This new version couldn't exist without you!

Now, we need your help once again to spread word about the app, because the project will only be a success if there are thousands of people taking data worldwide. So please post news about it on social media, tell your friends about the app, and give it a good rating in the app and play stores to help make it more visible!

If you'd like some more information, you can read our press release. Step-by-step guides for using the app are available for iOS and Android.