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Author |
Bará, S. |
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Title |
Variations on a classical theme: On the formal relationship between magnitudes per square arcsecond and luminance |
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Journal Article |
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Year |
2017 |
Publication |
International Journal of Sustainable Lighting |
Abbreviated Journal |
Intl J of Sustainable Lighting |
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Volume |
19 |
Issue |
2 |
Pages |
77 |
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Keywords |
Instrumentation; skyglow; luminance; magnitude; sky brigthness; photometry |
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Abstract |
The formal link between magnitudes per square arcsecond and luminance is discussed in this paper. Directly related to the human visual system, luminance is defined in terms of the spectral radiance of the source, weighted by the CIE V(l) luminous efficiency function, and scaled by the 683 lm/W luminous efficacy constant. In consequence, any exact and spectrum-independent relationship between luminance and magnitudes per square arcsecond requires that the last ones be measured precisely in the CIE V(l) band. The luminance value corresponding to mVC=0 (zero-point of the CIE V(l) magnitude scale) depends on the reference source chosen for the definition of the magnitude system. Using absolute AB magnitudes, the zero point luminance of the CIE V(l) photometric band is 10.96 x 104 cd·m-2. |
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Address |
Departamento de Física Aplicada, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain; salva.bara(at)usc.es |
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English |
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English |
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ISSN |
2586-1247 |
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Call Number |
IDA @ john @ |
Serial |
2162 |
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Author |
Bará, S.; Escofet, J. |
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Title |
On lamps, walls, and eyes: The spectral radiance field and the evaluation of light pollution indoors |
Type |
Journal Article |
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Year |
2018 |
Publication |
Journal of Quantitative Spectroscopy and Radiative Transfer |
Abbreviated Journal |
J of Quant Spect and Rad Trans |
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Volume |
205 |
Issue |
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Pages |
267-277 |
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Keywords |
Instrumentation; Light pollution; Artificial light at night; Light field; Radiance field; Radiometry; Photometry |
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Abstract |
Light plays a key role in the regulation of different physiological processes, through several visual and non-visual retinal phototransduction channels whose basic features are being unveiled by recent research. The growing body of evidence on the significance of these effects has sparked a renewed interest in the determination of the light field at the entrance pupil of the eye in indoor spaces. Since photic interactions are strongly wavelength-dependent, a significant effort is being devoted to assess the relative merits of the spectra of the different types of light sources available for use at home and in the workplace. The spectral content of the light reaching the observer eyes in indoor spaces, however, does not depend exclusively on the sources: it is partially modulated by the spectral reflectance of the walls and surrounding surfaces, through the multiple reflections of the light beams along all possible paths from the source to the observer. This modulation can modify significantly the non-visual photic inputs that would be produced by the lamps alone, and opens the way for controlling—to a certain extent—the subject's exposure to different regions of the optical spectrum. In this work we evaluate the expected magnitude of this effect and we show that, for factorizable sources, the spectral modulation can be conveniently described in terms of a set of effective filter-like functions that provide useful insights for lighting design and light pollution assessment. The radiance field also provides a suitable bridge between indoor and outdoor light pollution studies. |
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Address |
Área de Óptica, Departamento de Física Aplicada, Universidade de Santiago de Compostela, Santiago de Compostela, Galicia, Spain; salva.bara(at)usc.es |
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Elsevier |
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English |
Summary Language |
English |
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0022-4073 |
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IDA @ john @ |
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2163 |
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Author |
Zeng, X.; Shao, X.; Qiu, S.; Ma, L.; Gao, C.; Li, C. |
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Title |
Stability Monitoring of the VIIRS Day/Night Band over Dome C with a Lunar Irradiance Model and BRDF Correction |
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Journal Article |
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Year |
2018 |
Publication |
Remote Sensing |
Abbreviated Journal |
Remote Sensing |
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Volume |
10 |
Issue |
2 |
Pages |
189 |
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Keywords |
Instrumentation; Remote Sensing |
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Abstract |
The unique feature of the Visible Infrared Imager Radiometer Suite (VIIRS) day/night band (DNB) is its ability to take quantitative measurements of low-light scenes at night. In order to monitor the stability of the high gain stage (HGS) of the DNB, nighttime observations over the Dome C site under moonlight are analyzed in this study. The Miller and Turner 2009 (MT2009) lunar irradiance model has been used to simulate lunar illumination over Dome C. However, the MT2009 model does not differentiate the waxing and waning lunar phases. In this paper, the MT-SWC (SeaWiFS Corrected) lunar irradiance model differentiating the waxing and waning lunar phases is derived by correcting the MT2009 model using lunar observations made by the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS). In addition, a top of atmosphere (TOA) bi-directional reflectance distribution function (BRDF) model during nighttime over Dome C is developed to remove the angular dependence from the nighttime TOA reflectance. The long-term stability monitoring of the DNB high-gain stage (HGS) reveals a lower reflectance factor in 2012 in comparison to the following years, which can be traced back to the change in relative spectral response (RSR) of National Oceanic & Atmospheric Administration’s (NOAA’s) Interface Data Processing Segment (IDPS) VIIRS DNB in April 2013. It also shows the radiometric stability of DNB data, with long-term stability of less than 1.58% over the periods from 2013 to 2016. This method can be used to monitor the radiometric stability of other low-light observing sensors using vicarious calibration sites under moonlight illumination. |
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2072-4292 |
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LoNNe @ kyba @ |
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1805 |
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Author |
Jechow, A.; Ribas, S.J.; Domingo, R.C.; Hölker, F.; Kolláth, Z.; Kyba, C.C.M. |
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Title |
Tracking the dynamics of skyglow with differential photometry using a digital camera with fisheye lens |
Type |
Journal Article |
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Year |
2018 |
Publication |
Journal of Quantitative Spectroscopy and Radiative Transfer |
Abbreviated Journal |
Journal of Quantitative Spectroscopy and Radiative Transfer |
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Volume |
209 |
Issue |
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Pages |
212-223 |
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Keywords |
Skyglow; Instrumentation |
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Abstract |
rtificial skyglow is dynamic due to changing atmospheric conditions and the switching on and off of artificial lights throughout the night. Street lights as well as the ornamental illumination of historical sites and buildings are sometimes switched off at a certain time to save energy. Ornamental lights in particular are often directed upwards, and can therefore have a major contribution towards brightening of the night sky. Here we use differential photometry to investigate the change in night sky brightness and illuminance during an automated regular switch-off of ornamental light in the town of Balaguer and an organized switch-off of all public lights in the village of Àger, both near Montsec Astronomical Park in Spain. The sites were observed during two nights with clear and cloudy conditions using a DSLR camera and a fisheye lens. A time series of images makes it possible to track changes in lighting conditions and sky brightness simultaneously. During the clear night, the ornamental lights in Balaguer contribute over 20% of the skyglow at zenith at the observational site. Furthermore, we are able to track very small changes in the ground illuminance on a cloudy night near Àger. |
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0022-4073 |
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LoNNe @ kyba @ |
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1807 |
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Author |
Tamir, R.; Lerner, A.; Haspel, C.; Dubinsky, Z.; Iluz, D. |
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Title |
The spectral and spatial distribution of light pollution in the waters of the northern Gulf of Aqaba (Eilat) |
Type |
Journal Article |
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Year |
2017 |
Publication |
Scientific Reports |
Abbreviated Journal |
Sci Rep |
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Volume |
7 |
Issue |
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Pages |
42329 |
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Keywords |
Measurement; Instrumentation; Remote Sensing |
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Abstract |
The urbanization of the shores of the Gulf of Aqaba has exposed the marine environment there, including unique fringing coral reefs, to strong anthropogenic light sources. Here we present the first in situ measurements of artificial nighttime light under water in such an ecosystem, with irradiance measured in 12 wavelength bands, at 19 measurement stations spread over 44 square km, and at 30 depths down to 30-m depth. At 1-m depth, we find downwelling irradiance values that vary from 4.6 x 10(-4) muW cm(-2) nm(-1) 500 m from the city to 1 x 10(-6) muW cm(-2) nm(-1) in the center of the gulf (9.5 km from the city) in the yellow channel (589-nm wavelength) and from 1.3 x 10(-4) muW cm(-2 )nm(-1) to 4.3 x 10(-5) muW cm(-2) nm(-1) in the blue channel (443-nm wavelength). Down to 10-m depth, we find downwelling irradiance values that vary from 1 x 10(-6) muW cm(-2 )nm(-1) to 4.6 x 10(-4) muW cm(-2) nm(-1) in the yellow channel and from 2.6 x 10(-5) muW cm(-2) nm(-1) to 1.3 x 10(-4) muW cm(-2) nm(-1) in the blue channel, and we even detected a signal at 30-m depth. This irradiance could influence such biological processes as the tuning of circadian clocks, the synchronization of coral spawning, recruitment and competition, vertical migration of demersal plankton, feeding patterns, and prey/predator visual interactions. |
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School of Agriculture and Environmental Studies, Beit Berl College, Kfar Saba, Israel |
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English |
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2045-2322 |
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Notes |
PMID:28186138; PMCID:PMC5301253 |
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Call Number |
GFZ @ kyba @ |
Serial |
1861 |
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