The new World atlas of artificial night sky brightness

Transcription

1 CieloBuio ISTIL The new World atlas of artificial night sky brightness Fabio Falchi, Pierantonio Cinzano, Dan Duriscoe,, Chris Kyba,, Chris Elvidge, Kim Baugh, Boris Portnov, Nataliya Rybnikova, Riccardo Furgoni Starlight, Beyond Light Pollution La Palma, Canary Islands, 1-8 July 2016

2 Comparison of the two atlases Satellite/Instrument Satellite Resolution Year (n. of nights) Coverage Ground night sky brightness data Upward function Computation WA 1 DMSP-OLS km 1996/97 (28 nights) Mosaic covering continents 70 Standard At sea level New Atlas NPP-VIIRS-DNB 750 m 2014 (6 months of nomoon nights) Complete from 75 N to 60 S 163 CCD 30,000+ SQM-L Three parameters Altitude

3 Pitfalls in comparing to old atlas Old atlas was calibrated with earl night measurements (this alone may give a 30% or more difference with the 1 a.m. of the new atlas) New high blue content lights (mainly LEDs) unterestimated by satellites, but very pollutant for our scotopic vision and detected by the SQMs. Not present in 1996/97. Different natural levels used in the two atlases Old atlas computed for sea level Different colour steps

4 Outlines of the Method The radiance data from VIIRS was divided in 60 tiles covering 75 N to 60 S The zenith brightness for each site was computed: considering the light sources in a radius of 195 km Taking into account for Earth curvature and altitude of terrain Using a standard US62 clean atmosphere with Garstang parameter K=1 (it corresponds to horizontal visibility of x=26 km, optical depth τ=0.3, vertical extinction at sea level of m=0.33 mag in the V band, m=0.21 mag at 1000m and m=0.15 mag at 2000 m) Using three different upward functions Searching for the best fit of the linear combination of the three maps to the night sky brightness data The calibrated final map was colour coded in two-fold steps from 1% of the natural brightness to 41 times or more the natural

5 Upward intensity function(s) Panel prepared by Dan Duriscoe

6 Upward intensity function(s) Panel prepared by Dan Duriscoe

7 Upward intensity function(s) Panel prepared by Dan Duriscoe

8 Upward intensity function(s) Panel prepared by Dan Duriscoe

9 Upward intensity function(s) Panel prepared by Dan Duriscoe

10 Upward intensity function(s) Panel prepared by Dan Duriscoe

11 Natural brightness The assumed value for the natural brightness is the median value of zenith sky luminance for mid-northern latitudes: 0.17 mcd m -2 or mag arcsec -2

12 Calibration with brightness measures

13 Calibration with brightness measures

14 Calibration with brightness measures

15 Calibration with brightness measures

16 Pitfalls in comparing to observations Predictions and observations may differ for several reasons: Natural brightness is highly variable ( µcd m -2 ) Measurements taken with wide field instruments includes stars and brighter than zenith portions of sky Proximity of non standard lights, such as gas-flares, volcanic eruptions, lights from fishing boats Non standard upward functions Screening by mountains Different atmospheric conditions than assumed for the model

17 The new World atlas of artificial night sky brightness

18 The new World atlas of artificial night sky brightness

19 Europe

20 Europe

21 Impact on visual observing 1500 km 950 km

22 Visual observing impact

23 Visual observing impact

24 Visual observing impact

25 Visual observing impact

26 Visual observing impact

27 Visual observing impact

28 Visual observing impact Natural sky (NPS CCD data)

29 Visual observing impact Natural sky (NPS CCD data)

30 Visual observing impact Sky polluted near horizon

31 Visual observing impact Sky polluted near horizon

32 Visual observing impact Degraded to Zenit

33 Visual observing impact Degraded to Zenit

34 Visual observing impact Natural sky lost

35 Visual observing impact Natural sky lost

36 Visual observing impact Milky Way invisible

37 Visual observing impact Milky Way invisible

38 Visual observing impact No dark adaption

39 Visual observing impact No dark adaption

40 World population living under sky Some statistics 14% 8% 9% Fraction of population living under skies: 22% 19% Natural sky Degraded toward the horizon degraded at zenith Natural sky lost Milky Way lost Cones active 28%

41 UE population living under sky 0% 0% 6% 21% 34% Natural sky Degraded toward the horizon degraded at zenith Natural sky lost Milky Way lost Cones active 39%

42 USA population living under sky 0% 0% 3% 20% 37% Natural sky Degraded toward the horizon degraded at zenith Natural sky lost Milky Way lost Cones active 40%

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47 Madrid Berlin

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50 North America

51 Asia

52 South Asia

53 Africa

54 Australia and New Zealand

55 Canary islands

56 Media coverage and Altmetric score

57 Video and interactive maps 4TYBVig

58 CieloBuio ISTIL Thank You! Starlight, Beyond Light Pollution La Palma, Canary Islands, 1-8 July 2016

59 World Atlas 1 coverage

60 World Atlas 1 coverage

61 VIIRS DNB spectral response

62 Hawaii