1. Sky Brightness Measurements with a Digital Camera: The Effect of a Small Nearby Village (Großmugl) on Night Sky Brightness Georg Zotti Wiener Arbeitsgemeinschaft für Astronomie & Österreichischer Astronomischer Verein

2. Georg Zotti 1 Outline Sky Luminance and Stellar Visibility High Dynamic Range Photography Evaluation of HDR images Urban vs. Rural Night Sky Großmugl Experiment, Astronomy Day 2008

3. Georg Zotti 2 Sky Luminance and Stellar Visibility Instrument Vision Human Vision [after Weaver 1947, Garstang 1986, Cinzano 1997] Full Moon Sunset

4. Georg Zotti 3 High Dynamic Range Photography Combination of several exposures Calibration with Luminance Meter  Luminance Map  Photographic Measurement System

5. Georg Zotti 4 Our System Camera: Digital SLR All-Sky Fisheye only with Full-Size Chip DSLRs RAW image format! Free Software: Dcraw for RAW image processing http://cybercom.net/~dcoffin/dcraw/ http://cybercom.net/~dcoffin/dcraw/ PFS Tools for HDR processing http://www.mpi-inf.mpg.de/resources/pfstools/ http://www.mpi-inf.mpg.de/resources/pfstools/ Extensible via GNU Octave Calibration: PFS Tools, from EXIF data (approximative) Minolta LS-110 for daylight range Sky Quality Meter for night sky measurements

6. Georg Zotti 5 Evaluation of Zenith Luminance Series of HDR photos Averaged zenith area  Tonemapped HDR images

7. Georg Zotti 6 Evaluation of Zenith Luminance cd/m² Sun alt.

8. Georg Zotti 7 Results: Surburb Sky Full illuminationReduced illumination

9. Georg Zotti 8 Results: Surburb Sky Full illuminationReduced illumination

10. Georg Zotti 9 Results: City Border (average) Full illuminationReduced illumination

11. Georg Zotti 10 Results: City Border (good night) Full illuminationReduced illumination

12. Georg Zotti 11 Results: City Border / 20km from Vienna mag5.5Großmugl near Vienna, mag6 Vienna

13. Georg Zotti 12 Results: 20km from Vienna / Unpolluted Großmugl near Vienna, mag6.2Pristine Sky (Mongolia) mag6.3 Vienna

14. Georg Zotti 13 Results: 20km from Vienna / Unpolluted Großmugl near Vienna, mag6.2Pristine Sky (Mongolia) mag6.3

15. A Rare View: Dark Clouds at Night! Georg Zotti 14

16. Astronomy Day, 2008-05-10, Großmugl Georg Zotti 15 2 illuminated roads 1 illuminated road Lights off BLACK

17. Astronomy Day, 2008-05-10, Großmugl Georg Zotti 16 Lights off 1 illuminated road, 10 minutes after power-on Back to „normal“ BLACK Vienna Großmugl

18. Astronomy Day, 2008-05-10, Großmugl Georg Zotti 17 Lights off Back to „normal“ BLACK Vienna Großmugl

19. Open Questions Calibration: Reference photometer not sensitive enough for dark scene SQM sensitivity non-photopic What is the „best“ sky brightness unit? cd/m² mag/arcsec² Limiting visual magnitude Can we agree on a common colour scale? Georg Zotti 18

20. Street Luminaires at Kuffner Observatory Georg Zotti 19 Last Sunday Street lamp Moon Tuesday

21. Georg Zotti 20 Conclusions All-Sky Luminance Measurement System Calibrated HDR Imaging System Simple extensions to PFS Tools  False-Colour Plots For “technical” astronomers: mag/arcsec² For visual star watching: limiting visual magnitudes Addition of PFS base units: cd/m² Light Pollution in rural areas ruins esp. horizon sky Effect of road light reduction clearly visible Thank you for Your Attention Georg Zotti