1. First results from the Loss of the Night app Christopher Kyba, Annette Krop-Benesch, Franz Hölker Freie Universität Berlin / IGB 13 th European Symposium 2013 Pamplona, Spain September 14, 2013

2. Background: GLOBE at Night

3. NELM Kyba et al. Sci Rep (2013)

4. Problems with GaN Can’t identify constellations in the city Δ m is fairly large for individual observations (~1.2 mag) Atmospheric correction?

5. Solution: Verlust der Nacht app! Part of BMBF Wissen- schafts Jahr 2012 Programmed by Cosalux Based upon Google Sky program Lots of information about artificial light at night inside app

7. Star selection From 10 o to 45 o from zenith Mag<5.2 Only ~1000 stars already in Google app

8. Star selection: Stage 1 Is star found? Start: Identify brightest star in sky (m new ) Assign user new star with m new Identify new star in range m+0.5<m new <m+1 Identify new star in range m+0.5<m new <m+1 Yes Proceed to Stage 2 Proceed to Stage 2 No

9. Star selection: Stage 2 New star: 10% brighter 70% slightly fainter 20% much fainter New star: 10% brighter 70% slightly fainter 20% much fainter Yes No Identify much brighter star m-1.5<m new <m-0.5 Identify much brighter star m-1.5<m new <m-0.5 Assign user star with m new Is star found? New star: 50% much brighter 40% slightly brighter 10% slightly fainter New star: 50% much brighter 40% slightly brighter 10% slightly fainter Unsure

10. Example Data 1 2 3 4 5 Stellar magnitude Time (minutes) 0

11. Dresden observations 1 2 3 4 5 Stellar magnitude Time (minutes) not visible 0

12. Dresden observations 1 2 3 4 5 Stellar magnitude Time (minutes) not visible not sure 0 Cinzano ~4.66 Fit ~4.0 (0.9)

13. Global app usage

14. Data submission over time April June August 1000 200

15. Data submission over time April June August Good observation % 0 50 100

16. Faintest stars in app have mag ~5 App is only designed for urban astronomy! Problem: Not enough urban data

17. Cinzano pop>9b n –Germany: 25% –Greece: 47% –Japan: 63% –Spain: 57% –USA: 62% –EU: 38% Cinzano pop>27b n –Germany: 0% –Greece: 17% –Japan: 27% –Spain: 25% –USA: 30% –EU: 8% NELM<4NELM<4.8 App users: 21% GaN: 32% App users: 2% GaN: 6%

18. Which stars are best? Megrez (HR 4660) –mag 3.31 –20 seconds –Found 91% –Unsure 3% –Easier star Edasich (HR 5744) –mag 3.29 –31 seconds –Found 66% –Unsure 18% –Harder star Big Dipper Draco

19. Need more urban users! Expansion to 10 languages Loss of the Night blog: www.lossofthenight.blogspot.com Search for additional funding Going forward

20. Acknowledgements Title illustration: Light pollution It’s not pretty: Jeremy Stanley (Wikimedia Commons) The app and our project is funded through: Verlust der Nacht German Ministry of Education and Research BMBF-033L038A Thanks to Google for making Sky Map source code available, to GLOBE at Night for consulting in the app development, and to app testers!

21. Urban park in Berlin 1 2 3 4 5 Stellar magnitude Time (minutes) not visible not sure

22. Maximum likelihood fit Probability 5 3 1 NELM 1 0

23. Maximum likelihood fit Probability 5 3 1 NELM 1 0

26. Citizen Science Works! Observed sky brightness Sternenhimmel 100x Sternenhimmel Sky brightness