Help measure how the night sky is changing

On March 14 and September 12 2015, you can join thousands of people around the world in measuring how bright the night sky is where you live. The results from this experiment will help scientists to understand how the night sky is changing over time, as cities switch to LED street lighting. All you need is a place that’s not too close to any street lamps where you have a view of a good portion of the night sky, and clear skies on that night.

View of the Orion Constellation at three different levels of skyglow. Which one looks like your night sky?. Credits: Christopher Kyba

View of the Orion Constellation at three different levels of skyglow. Which one looks like your night sky?. Credits: Christopher Kyba

There are three ways to take part:

1. Globe at Night

In Globe at Night, citizen scientists compare the visibility of the stars in constellations like Orion to a set of star charts (see above). You can either print the charts out in advance and report online later, or use their webapp on your smartphone. Globe at Night information is available in 26 languages.

2. Loss of the Night app

The loss of the Night app directs you to specific stars in the sky, and asks whether you can see them with your own eyes or not. The faintest star that you are able to see tells us how bright the sky is. The app runs in 15 languages, and detailed instructions on how to use the app in iOS or Android are available on the project blog.

3. Dark Sky Meter app

The Dark Sky Meter app uses the iPhone’s camera to directly measure how bright the night sky is. You first take a dark image with the phone in your pocket to calibrate the camera, then point the phone straight up into the sky and take a second photo. The app is available in a lite and full version. Click for more information and maps of observations.

What to do if it’s cloudy

If it’s cloudy on March 14 you can try again on any night up until March 20. The reason for the International Nights of Skyglow Observation is to synchronize as much data at the same time of year as possible. You can actually take part in all three of these experiments all year long (any time that the moon is not up). Try observing again as the year goes on, and find out what time of year is best to go stargazing where you live!

Does this really work?

Random people without any specialized training looking up at the sky… is this really science? It is, and it has a special name: Citizen Science! Truth be told, each individual observation from these campaigns is not particularly reliable on its own. But by averaging the results of thousands of observers, very precise measurements of the rate of change of skyglow are possible.

Why March 14?

This year, March 14 has a special significance. If you are able to, make your observation at 9:26pm, and you’ll be a part of “Super π day” (3/14/15 9:26)!

Additional information

Artificial light allows us to extend our activity into the night both indoors and outdoors, but it unfortunately comes with some negative side effects, such as less sleep. Light that shines outdoors produces skyglow, as seen in the photos below:

Credits: Andreas Hänel

Credits: Andreas Hänel

The image on the right shows the Milky Way inside of the Westhavelland International Dark-Sky Reserve. Above the park, thousands of stars shine brightly against a dark background. At the horizon, however, lights from cities like Berlin spoil the view. The photo on the left was taken with the same camera, lens, and settings in a backyard garden on the outskirts of Osnabrück, Germany. Far fewer stars are visible because of the artificial glow of the sky. As one moves closer to a city, the Milky Way disappears, and eventually only the very brightest stars, planets, and the moon can be seen at night.

Solid state lighting like LEDs is going to change how the sky glows, but for the moment, we don’t know whether it’s going to get brighter or darker. There are reasons to be optimistic: solid state lighting can be more easily directed, allowing cities to shine light where it is needed. Ideally, poorly designed lamps shining directly into bedroom windows and up into the sky should be a thing of the past. However, LED lighting often has a large blue component. Blue light is more likely to be scattered by the atmosphere, so it could make the sky brighter. The only way we can find out what’s going on globally is with the help of people like you! By repeating the same measurement in future years, together we will be able to measure the rate at which the sky is getting brighter or darker.


Credit: Copyright Photo Phil Dera.

Credit: Copyright Photo Phil Dera.

Christopher Kyba studies the ecological impact of artificial light in the nighttime environment at the German Research Center for Geoscience (GFZ) in Potsdam. His work mainly focuses on quantifying the flux of light emitted upward by cities (using aerial or satellite observations), and the light that is returned back to Earth as skyglow. One of his current research interests is in examining observations made by citizen scientists in order to understand how skyglow is changing with the introduction of LED lamps.

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12 thoughts on “Help measure how the night sky is changing

  1. I would think it might also be useful to have a digital photo of the sky with a specific ISO, shutter speed, f-stop and perhaps a lens length. Something like: ISO 100, shutter 1/60 sec, f-4.5, lens length 35mm or whatever values would make the most sense. (Similar to #3 above but with a DSLR camera or equivalent.) Would this be useful? Perhaps not because of the variation in cameras?

    • Hi Dan,

      It’s possible to measure sky brightness in that way. In fact, the very best documentation of the night sky is taken by the US National Parks Service with a digital camera mounted on a robotic stage.

      But when it comes to citizen observations, you are correct that the calibration is a difficult problem. I don’t doubt that someone could devise a project to do this, but it’s a lot easier to find participants worldwide when nothing more than an internet connection is needed (as in Globe at Night’s case).

      There is, however, a project to let people track changes in local lighting using any digital cameras. You can find out more here: http://guaix.fis.ucm.es/sites/guaix.fis.ucm.es.splpr/files/timeline/TimeLine_EN_vb.pdf

  2. Have you been in contact with Dr. Daniel Duriscoe of the U.S.National Park Service. He has been making scientific measurements and analyzing same at the national parks in the U.S. His data may be useful to your study. He may want to collaborate as well.

  3. Hmm… I think my first post didn’t take for some reason. I was suggesting that you contact Dr. Daniel Duriscoe of the US National Park Service. He has been doing night sky research for 15 years.

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