ueck 2011 - Andreić at al: Light Pollution in the Near Infrared 1 Light Pollution in the Near Infrared Ž. Andreić 1 , D. Andreić 2 and K. Pavlić 1 1 Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, Pierottijeva 6, 10 000 Zagreb, Croatia E-mail: [email protected], [email protected]2 Faculty of Veterinary Medicine, University of Zagreb, Heinzelova 55, 10 000 Zagreb, Croatia. E- mail: [email protected]
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Osnabrueck 2011 - Andreić at al: Light Pollution in the Near Infrared 1 Light Pollution in the Near Infrared Ž. Andreić 1, D. Andreić 2 and K. Pavlić 1.
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Osnabrueck 2011 - Andreić at al: Light Pollution in the Near Infrared 1
Light Pollution in the Near Infrared
Ž. Andreić1, D. Andreić2 and K. Pavlić1
1Faculty of Mining, Geology and Petroleum Engineering, University of Zagreb, Pierottijeva 6, 10 000 Zagreb, Croatia E-mail: [email protected], [email protected]
2Faculty of Veterinary Medicine, University of Zagreb, Heinzelova 55, 10 000 Zagreb, Croatia. E-mail: [email protected]
Osnabrueck 2011 - Andreić at al: Light Pollution in the Near Infrared 2
Overview
1. Introduction2. CCD and C-MOS cameras3. visible and infrared sky4. past and future5. conclusions
Osnabrueck 2011 - Andreić at al: Light Pollution in the Near Infrared 3
Introduction
Light pollution (LP) is usually conected to human vision, so only visible part of EM radiation (light) is considered in studies of LP.
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CCD cameras are sensitive to infra-red (IR) up to 1000 nm!
and there is "LP" in this spectral region too!
IR
C-MOS
CCD
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Modified DSLR camera with filters
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1.0
300 400 500 600 700 800 900 1000 1100
Wavelength (nm)
Re
lati
ve
sp
ec
tra
l s
en
sit
ivit
y
UV-IR cut
RG-830
no filter
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Light sources at the horizon can be hiden by a circular lens hood covering horizon up to 10o altitude.
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semi-rural sky, SQM-L: 20.2 at zenith, UV-IR cut
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same sky, RG830 (IR)
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Results
10%
20%
Visible Infrared
0 30 60 90 0 30 60 90
iso-photeeach
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Monitoring methods: modified DSLR + spectrograph
- Fast prismatic spectrograph
- covers 420-1100 nm
- wavelength calibration lamp integrated
- records natural sky spectrum in 5 min at ISO 1600 with a modified DSLR
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LP spectrum, same place
Ne comparison
Sky spectrum around zenith
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Results
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400 500 600 700 800 900 1000 1100
wavelength (nm)
inte
nsi
ty (
a.u
.)
Na 818,3 nmHP Nalamps
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HP-Na bulbs are the culprit!
HP-Na
sky
MH
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possible solutions
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400 500 600 700 800 900 1000 1100
wavelength (nm)
inte
nsi
ty (
a.u
.)
RG 850
custom interference filter?
H
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Past and future:
HP mercury
HP sodium
metal halide
Incandescent halogen
"white" LED
IRvisible
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Conclusions
1. There is strong LP in the near infrared, and it is produced by the same sources responsible for the LP in the visible part of the spectrum. Sodium bulbs produce very strong IR LP.
2. IR is not as crowded with LP spectral lines as visible part of the spectrum, good filtering is still possible.
3. Scattering of the IR light is not as effective as for the visible light, so the IR sky quality is little better. Also, natural sky brightness is higher in the IR, making LP less prominent.
4. Light cirrus clouds are often prominent in the IR, but are invisible in the visible light.
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Conclusions 2
5. New metal-halide (MH) lamps polute more than sodium HP lamps, both in the visible and in the IR .
6. LED sources polute only in the visible, but show a very worrysome excess of blue light, that should be filtered at the source at any cost.
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The speaker‘s attendance at this conference was sponsored by
the Alexander von Humboldt Foundation.
http://www.humboldt-foundation.de
Acknowledgements
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