The view from your app

Last night marked 167 years since the planet Neptune was first observed from the Berlin Observatory, within 1° of where Urbain Le Verrier had predicted it would be. I recently took a photo of the sky from the crossing of Friedrichstraße and Unter den Linden (which is close to the site of the original Berlin Observatory, but about about 2 km from the location where Neptune was observed). Here's the sky over Berlin today:

Night sky over central Berlin by Christopher Kyba
is licensed under a Creative Commons Attribution 3.0 Unported License.

For comparison, I used the same camera and same settings to take another image of the sky during a star party at Naturpark Westhavelland, 82 km from where the first image was taken. The sky over Berlin was probably only a little bit brighter than this when Neptune was discovered:

Night sky over Naturpark Westhavelland by Christopher Kyba
is licensed under a Creative Commons Attribution 3.0 Unported License.

By 1913 the Berlin Observatory was forced to move outside of the city for three reasons: increasing light pollution, air pollution (aerosols), and shaking of the instruments caused by the passing of the nearby S-bahn trains. Researchers still work the Leibniz-Institut für Astrophysik Potsdam (as the Berlin Observatory is known today), but they generally no longer make optical observations at the site due both to the skyglow of Berlin and our area's tendency to inclement weather.

Neptune is quite bright, so it should still be possible to observe it from the center of Berlin today with binoculars, as long as you know where to look. Thanks to Axel Schwope from Leibniz-Institut für Astrophysik Potsdam for telling me about the history of Berlin Observatory yesterday.

Urban Astronomy with the Loss of the Night App

I made a presentation about the loss of the night app at the 13th European Symposium for the Protection of the Night Sky, and I wanted to share two important slides here. The first shows what fraction of our app users live under bright, or very bright skies:

The "Cinzano pop" tables show what population of the given countries were estimated in 2001 to live under skies 9 times or 27 times brighter than natural. At the bottom, we see that contributors to GLOBE at Night and our app users are drawn from a population that is biased towards less polluted areas. This is a problem, because the app is designed for urban astronomy! It only has the ~1000 brightest stars in its database, all of which have a magnitude less than 5.  This means that more than 80% of all of our app users are making observations in areas that are too dark for the app to function properly!

There are three reasons why we don't have fainter stars in the app. First, we were on a tight money/time budget, so we just used the stars that were already in Google's Sky Map app. Second, if you are in an area with little skyglow, there are just so many stars in the sky that it's hard to tell which one the app is asking you to look for! Third, at some point the screen of the mobile phone will be bright enough that it will ruin your night vision and make it impossible to see the stars. Based on our testing, this isn't a problem in cities, but it would be in the countryside.

Does this mean that 80% of the data we have collected so far is useless? Far from it! Take a look at the next slide:

Here we compare two stars that are no so far away from each other in the Northern Hemisphere, Megrez in the Big Dipper and Edasich in Draco. You can see where the stars are relative to their constellations in the next two images:

Megrez is the central star of the Big Dipper.

Edasich is a part of a much larger constellation.

The two stars have a very similar brightness, but Megrez is part of the Big Dipper, probably the most familiar constellation in the Northern Hemisphere. Edasich, on the other hand, is part of Draco, a much more difficult constellation to observe. Because of this, our app users are able to make a decision about Megrez more quickly (20 seconds on average), and their decision is more accurate (nearly all of our app users should have been able to see both stars).

By using the app in an area without light pollution, you are helping us to understand which stars are easier to make quick, accurate decisions about, and which are harder. Once we have enough data about the 1000 stars in the database, we'll be able to preferentially assign easier stars to users. This will reduce the number of incorrect classifications, and will probably also make the app more fun. So use the app wherever you happen to be, but please tell your friends living in cities to try out the app!

The view from your app

Yesterday we saw some examples of bad street lighting from Spain. Today app user Andreas Hänel provides us with some good examples of decorative street lighting, from Puente la Reina, Spain. Until recently, Puente la Reina was overlit with lamps that produced a lot of glare, and sent much of their light into bedroom windows and into the sky. Now, you can see that the streets are well lit, but that the house facades are quite dark, and there is almost no glare from the decorative street lamps:

Good decorative street lighting, Puente la Reine by Andreas Hänel is licensed under a Creative Commons Attribution 3.0 Unported License.

In this photo from the Plaza Julián Mena, you can see an example of both poor and excellent decorative lighting:

Decorative street lighting in Plaza Julián Mena by Andreas Hänel is licensed under a Creative Commons Attribution 3.0 Unported License.

The lamp at top left wastes a large fraction of the light that it produces, by sending much of the light where it's not needed. The lamp at center right casts its light only downward, towards the ground. For comparison, here is the daytime view from Google street view. In Puente la Reina, before they changed the lighting many areas were extremely overlit. By directing the light better and using lower ground lighting levels, the town was able to cut its electricity consumption and energy bill drastically. The result is well lit streets, that are more attractive than they were before the lighting intervention.

The view from your app

App user Susana Malón Giménez showed the following images at the 13th European Symposium for the Protection of the Night Sky, and she gave me permission to post them here.

The first image shows badly glaring parking lot lighting:

Parking by Susana Malón Giménez is licensed under a Creative Commons Attribution 3.0 Unported License.

 
This type of lighting actually reduces your ability to see what's going on, which is not at all desirable in a parking lot!  The second image is titled no common sense:

No common sense by Susana Malón Giménez is licensed under a Creative Commons Attribution 3.0 Unported License.

The difficulty of the Spanish economy is awful for everyone in Spain. The only good news that I took from the visit is that Spanish cities are now very seriously confronting bad lighting. There were many talks which presented areas that were formerly over lit, where recent improvements in the lighting system have resulted in a massive energy savings. In many cases, the visibility in such areas has been greatly improved by removing glaring lights. You can see how this works in the following image:

Globo luminaria by Susana Malón Giménez is licensed under a Creative Commons Attribution 3.0 Unported License.

At first glance, did you see the two people under the lamps? Click to look at the full size image if you still can't see them. Globe lamps are often particularly bad for visibility, because they are not only glaring, but sometimes provide almost no light directly under them. Globe lamps are also particularly bad for the environment, because they shine more than half of their light upwards. It goes into trees where birds and bats live, and it goes into the sky, masking the Milky Way, and causing the sky to glow.

Later this week, I hope to present images of some of the the very good modernized lighting that we saw in Spain.

Kickstarter project for firefly documentary

I love fireflies. When we used to live in Philadelphia, crowds of people would gather on the edge of Clark Park in the early evenings in summer to watch them flashing. So I'm really looking forward to this new documentary about fireflies: Brilliant Darkness: Hotaru in the Night.

The film team has already gathered material, and now they need support to edit the film and do the voice over. You can help support the project by making a small donation at kickstarter. A $25 contribution gets you mentioned in the credits of the film and a free film download, and $50 gets you a DVD copy.

Crowdfunding only works if lots of people hear about the project, so if you love fireflies, let your friends know about the kickstarter campaign!

10,000 downloads!

I'm very pleased to say that the Loss of the Night app has now crossed 10,000 downloads, as reported by the Google Play page! The more users and observations we have, the more accurate the results will be, so please continue to spread word about the app. If you visit a friend with an android phone this weekend, you could both try using the app on your different phones, and see to what extent your observations agree with each other.

And if you happen to be on twitter, it would be great if you would re-tweet this tweet.

GLOBE at Night announces dates for 2014 campaign!

GLOBE at Night has announced the dates for the 2014 campaign:

This is the first year that the campaign will run all year long, so (depending on your latitude) you might be able to help out scientists like me with some summer stargazing! GLOBE at Night has been building a very useful time series of observations since 2006, and it's essential that it continue into the future. This spring, we published results showing that "citizen science provides valuable data for monitoring global night sky luminance". So please plan to take part in 2014!

For both the Loss of the Night app and GLOBE at Night, it's important the moon is set, and that's why the campaign only runs about 10 days per month. The GLOBE at Night dates are a bit conservative, but are a good guide for when the app will work. For example, in Berlin, we will have moon-free periods of astronomical darkness on January 17 (for 10 minutes), January 18 (1:14), and January 19 (2:19). With the app, you can try to make a measurement at any time. If the moon is out or twilight isn't over, then the app will warn you that it's "not dark enough".

The plan is that next year the Loss of the Night app data will be an official part of the GLOBE at Night campaign, so you should be able to see your observations on the GLOBE at Night interactive map. We're still sorting out the details, but I hope we'll have this ready in time for the campaign's start!