Friday, March 21, 2014

GLOBE at Night turns 8 years old!

The Loss of the Night app came about because of my research into the citizen science data from the GLOBE at Night project. The first GLOBE at Night data came in on March 22, 2006, so a few hours from now GLOBE at Night is going to turn 8 years old! Congratulations to Connie Walker, and everyone else on the GLOBE at Night team at NOAO!

The third GLOBE at Night campaign of 2014 begins tonight, and even if you prefer to use the Loss of the Night app or the Dark Sky Meter app, I hope that you will take a moment to take part in GLOBE at Night this month. The reason is that the time series for GLOBE at Night stretches back further, and observations taken using the same method are much easier to compare to each other. Since the original GLOBE at Night campaign began in March, additional observations from March each year are more important than those in any other month.

So if it's clear where you live, please take a few minutes to go outside and look up at the stars in the next ten days!

Wednesday, March 5, 2014

Skyglow over South Africa

Markus Pössel from the German Haus der Astronomie recently returned from South Africa, and realized that some of the photos he took nicely demonstrate the effect of skyglow. What's really great about the photos is that they not only have the same camera settings, he also set up the shot to be of the same part of the sky. He gave me permission to re-post the photos from his SciLogs post here.

He took three photos and overlaid them one above the other. The top photo shows the sky over Grahamstown (population 70,000). The middle photo has the same settings as the top, but was shot in Sutherland, near the South African Astronomical Observatory. The bottom photo is the same location as the middle photo, but with an exposure time twice as long to reveal more details.

Creative Commons License
An example of light pollution by Markus Pössel is licensed under a
Creative Commons Attribution-ShareAlike 4.0 International License.
The top two photos have identical camera settings,
the bottom photo had an exposure time that was twice as long.

The area of the sky that was photographed. The Southern
Cross is at the bottom. Constellation overlay via

You can get the full resolution version of the images at Markus's SciLogs post.

If you have a good image about skyglow or lighting, please send it to me, and I'll share it on the blog! You can see the entire light pollution photo series by clicking on the "view from your app" label below.

Monday, March 3, 2014

Multiple observations at the same location

I recently got a question via twitter:

Thanks for the question Aashay!

The answer is that multiple observations are extremely valuable to us, especially at this early stage. There are several reasons for this:
  • Observations from multiple people at the exact same time are very useful, because it helps us understand how different people perceive the night sky and how they interact with the app.
  • Observations from the same person at different times on a single night help us understand curfew effects (the sky over most cities gets darker as the night goes on).
  • Observations from the same person on different days at about the same time within the same month help us understand how consistent the app's results are with changing atmospheric conditions and clarity, as well as with the changing stars that it asks you for (there is some randomness built in). 
  • Observations from the same person several months apart are helpful for us because the stars change with the seasons. We are also trying to understand which stars are easier to decide upon and which are problematic, so the more stars you observe the better.
And finally, and most importantly, the main purpose of the app is to track long term changes in skyglow worldwide. For this to work, you need to sample the same location in a future year.

So please feel free to make observations as often as you like and observe as many stars as you like (going past 7 stars is helpful). But most of all, please plan to come back to the same location in the future and see if the sky has changed!

Wednesday, February 26, 2014

Passed 10,000 submitted observations!

The Loss of the Night app project passed an arbitrary (yet still exciting) milestone at the end of January: The 10,000th observation submitted to the GLOBE at Night server.  The number includes submissions with the test version of the app: we will probably cross 10,000 submissions by people running release 1.0.0 or higher tonight.

I promised to send a holographic postcard to the citizen scientist who submitted the complete observation closest to #10,000, but unfortunately the user is in Japan, and I think my (English) email informing the person that he or she has won a prize and asking for his or her mailing address may have been flagged as spam...  I am still trying to contact the contributor, but for now, let's celebrate observation #10,005, which was the second closest to #10,000.

Data from observation #10005

The observation was made inside of Luxembourg City, and was especially useful because 15 stars were observed instead of the minimum 7. Stars which were seen are marked in black, stars which were invisible are empty red circles, and stars that the user wasn't sure about are blue. The best fit for the naked eye limiting magnitude was 2.55 (solid line), with an estimated range of +/-0.6 over which the observer was likely to have trouble deciding whether the stars were visible or not.

In the next version of the app, we intend to provide instant feedback to you about what the naked eye limiting magnitude is at your site, and how consistent your results were. We will also do a much better job of sampling both sides of the estimated NELM, and we will get rid of most of the pesky stars that are hard to identify (did you hear that Draco?).

Locations where the app has been used.
Above is the most recent plot of all of the places on Earth that people have used the app (up to February 5). The black dots mark the 1208 places where the observations can be used for our analysis (no clouds, no twilight, no moonlight, and at least 7 stars observed), and the red dots show locations where this criteria wasn't met. It's fantastic that so many of you from around the world are contributing to the project, and I hope that we'll continue to increase add new citizen scientists as the year rolls on! Thank you for participation!

Thursday, February 20, 2014

Flashmob cancelled

Due to the poor weather forecast for tonight, we won't be holding a Flashmob for Science. The next event will take place in the USA, and I'll post information here when it's available. I hope that we will be able to hold a large event in Berlin this fall.

The 2nd GLOBE at Night period of 2014 has started, so if it's clear where you are tonight, then please go out and let us know how many stars you can see!

I am working on a grant application to improve the app, and because of that I will have very little time for posting in the next month. We have passed 10,000 submitted reports, and I hope that I will find some time to write about the two observations closest to #10,000 in the next weeks.

Friday, January 24, 2014

Great parking lot and terrible stair lighting

On a recent evening in Dresden, I noticed some great area lighting in a mall parking lot. As you can see below, the visibility in the parking lot is excellent.

In this closeup focused on the luminaires you can see that these types of lamps send almost no light directly up into the sky and are not at all glaring. Why isn't every parking lot in the world lit like this? Beats me...

Parking lot lighting (closeup) by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

Of course, it's impossible to tell by eye how bright it is. It's possible that these lamps are putting out more light than is necessary. It's also possible that they should have a warmer color. Regardless of whether these lamps were perfect or not, it's clear that they are excellent compared to the typical parking lot!

While I was visiting Dresden, I also noticed another example of how additional light can make your vision worse:

Dangerous lighting 1 by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

This lamp is intended to help people see, but it's right next to a stairway that is completely unlit due to bad positioning of the lamp! You can see how invisible the stairway is in these two photos from roughly the same angle:

Dangerous lighting 2 by Christopher Kyba is licensed
under a Creative Commons Attribution 4.0 International License.

In this case, you would actually be better of if the lamp wasn't there, and you were just navigating by artificial skyglow or moonlight.

Finally, a little contest. Comparing the last two photos, can you spot another lighting problem? Answer in the comments.

Monday, January 20, 2014

Nearing observation #10,000

Thanks to a big increase in the number of app users after releasing our expanded language version, we will reach observation number 10,000* in the next few days. To celebrate the milestone, I will send a holographic postcard showing Europe by day and night to the registered user who makes a complete observation (7 or more stars, no moon, no twilight, no clouds) with the observation number closest to 10,000.

This postcard could be yours!

The moon is away, GLOBE at Night 2014 has officially started, so get out and observe some stars tonight!

*This doesn't mean that we have 10,000 good data points, because most of these observations have in fact been submitted by people running the demo mode, using the app when it's partly cloudy, when the sun is not fully set, when the moon is up, or not making decisions on at least 7 stars. Depending on the month, about 10-20% of all observations fit the strictest requirements for analyzing the data.