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
Outline Sky Luminance and Stellar Visibility High Dynamic Range Photography h Evaluation of HDR images Urban vs. Rural Night Sky Großmugl Experiment, Astronomy Day 2008 Georg Zotti 1
Sky Luminance and Stellar Visibility Human Vision Full Moon Sunset Instrument Vision Georg Zotti [after Weaver 1947, Garstang 1986, Cinzano 1997] 2
High Dynamic Range Photography Combination of several exposures Calibration with Luminance Meter Luminance Map Photographic hi Measurement System Georg Zotti 3
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/ PFS Tools for HDR processing 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 Georg Zotti 4
Evaluation of Zenith Luminance Series of HDR photos Averaged zenith area Georg Zotti 5 Tonemapped HDR images
Evaluation of Zenith Luminance cd/m² Sun alt. Georg Zotti 6
Evaluation of Zenith Luminance Georg Zotti 7
Results: Surburb Sky Full illumination Reduced illumination Georg Zotti 8
Results: Surburb Sky Full illumination Reduced illumination Georg Zotti 9
Results: City Border (average) Full illumination Reduced illumination Georg Zotti 10
Results: City Border (good night) Full illumination Reduced illumination Georg Zotti 11
Results: City Border / 20km from Vienna mag5.5 Großmugl near Vienna, mag6 Vienna Georg Zotti 12
Results: 20km from Vienna / Unpolluted Großmugl near Vienna, mag6.2 Pristine Sky (Mongolia) mag6.3 Vienna Georg Zotti 13
Results: 20km from Vienna / Unpolluted Großmugl near Vienna, mag6.2 Pristine Sky (Mongolia) mag6.3 Georg Zotti 14
A Rare View: Dark Clouds at Night! Georg Zotti 15
Astronomy Day, 2008-05-10, Großmugl 2 illuminated roads Georg Zotti 16
Astronomy Day, 2008-05-10, Großmugl 2 illuminated BLACK roads 1 illuminated road Georg Zotti 17
Astronomy Day, 2008-05-10, Großmugl 2 illuminated BLACK roads BLACK 1 illuminated road Lights off Georg Zotti 18
Astronomy Day, 2008-05-10, Großmugl Großmugl Lights off Vienna Georg Zotti 19
Astronomy Day, 2008-05-10, Großmugl Großmugl Lights off BLACK 1 illuminated road, 10 minutes after power-on Vienna Georg Zotti 20
Astronomy Day, 2008-05-10, Großmugl Großmugl Lights off BLACK BLACK 1 illuminated road, 10 minutes after power-on Back to normal Vienna Georg Zotti 21
Astronomy Day, 2008-05-10, Großmugl Großmugl Lights off BLACK BLACK 1 illuminated road, 10 minutes after power-on Back to normal Vienna Georg Zotti 22
Astronomy Day, 2008-05-10, Großmugl Großmugl Lights off Vienna Georg Zotti 23
Astronomy Day, 2008-05-10, Großmugl Großmugl Lights off BLACK Back to normal Vienna Georg Zotti 24
Open Questions Calibration: Reference photometer not sensitive enough for dark scene SQM sensitivity non-photopic SQM (older model) field of view difficult What is the best sky bi brightness unit? cd/m² mag/arcsec² Limiting visual magnitude Can we agree on a common colour scale? Georg Zotti 25
Street Luminaires at Kuffner Observatory Last Sunday Moon Street lamp Georg Zotti 26
Street Luminaires at Kuffner Observatory Last Sunday Moon Tuesday Street lamp Georg Zotti 27
Street Luminaires at Kuffner Observatory Last Sunday Moon Tuesday Street lamp Georg Zotti 28
Street Luminaires at Kuffner Observatory Georg Zotti 29
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 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 <gzotti@cg.tuwien.ac.at> Georg Zotti 30