First results from the Loss of the Night app

Christopher Kyba, Annette Krop-Benesch, Franz HölkerFreie Universität Berlin / IGB

13th European Symposium 2013Pamplona, Spain

September 14, 2013

Background: GLOBE at Night

NELM

Kyba et al.Sci Rep (2013)

Problems with GaN

• Can’t identify constellations in the city

• Δm is fairly large for individual observations (~1.2 mag)

• Atmospheric correction?

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

Star selection

• From 10o to 45o from zenith

• Mag<5.2• Only ~1000

stars already in Google app

Star selection: Stage 1

Is star found?

Start: Identify brightest star in sky (mnew)

Assign user new star with

mnew

Identify new star in range

m+0.5<mnew<m+1

Yes

Proceed toStage 2

No

Star selection: Stage 2

New star:10% brighter

70% slightly fainter20% much fainter

Yes

No

Identify much brighter star

m-1.5<mnew<m-0.5

Assign user star with mnew

Is star found?

New star:50% much brighter

40% slightly brighter

10% slightly fainter

Unsure

Example Data

1

2

3

4

5

Ste

llar

mag

nit

ude

Time (minutes)

0

Dresden observations

1

2

3

4

5

Ste

llar

mag

nit

ude

Time (minutes)

not visible

0

Dresden observations

1

2

3

4

5

Ste

llar

mag

nit

ude

Time (minutes)

not visiblenot sure

0

Cinzano ~4.66Fit ~4.0 (0.9)

Global app usage

Data submission over time

April June August

1000

200

Data submission over time

April June August

Good

ob

serv

ati

on %

0

50

100

• Faintest stars in app have mag ~5• App is only designed for urban

astronomy!

Problem: Not enough urban data

Problem: Not enough urban data

Cinzano pop>9bn

– Germany: 25%– Greece: 47%– Japan: 63%– Spain: 57%– USA: 62%– EU: 38%

Cinzano pop>27bn

– 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%

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

• Need more urban users!• Expansion to 10 languages• Loss of the Night blog:

www.lossofthenight.blogspot.com• Search for additional funding

Going forward

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 ResearchBMBF-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!

Urban park in Berlin

1

2

3

4

5

Ste

llar

mag

nit

ude

Time (minutes)

not visiblenot sure

Maximum likelihood fitPr

obab

ility

531 NELM

1

0

Maximum likelihood fitPr

obab

ility

531 NELM

1

0

Citizen Science Works!

Observed sky brightness

Sternenhimmel

100x Sternenhimmel

Sky

brig

htne

ss