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Author  |
Bará, S.; Rigueiro, I.; Lima, R.C. |
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Title |
Monitoring transition: Expected night sky brightness trends in different photometric bands |
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Journal Article |
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Year |
2019 |
Publication |
Journal of Quantitative Spectroscopy and Radiative Transfer |
Abbreviated Journal |
Journal of Quantitative Spectroscopy and Radiative Transfer |
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Volume |
239 |
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Pages |
106644 |
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Keywords |
Skyglow; Remote Sensing; Instrumentation |
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Abstract |
Several light pollution indicators are commonly used to monitor the effects of the transition from outdoor lighting systems based on traditional gas-discharge lamps to solid-state light sources. In this work we analyze a subset of these indicators, including the artificial zenithal night sky brightness in the visual photopic and scotopic bands, the brightness in the specific photometric band of the widely used Sky Quality Meter (SQM), and the top-of-atmosphere radiance detected by the VIIRS-DNB radiometer onboard the satellite Suomi-NPP. Using a single-scattering approximation in a layered atmosphere we quantitatively show that, depending on the transition scenarios, these indicators may show different, even opposite behaviors. This is mainly due to the combined effects of the changes in the sources' spectra and angular radiation patterns, the wavelength-dependent atmospheric propagation processes and the differences in the detector spectral sensitivity bands. It is suggested that the possible presence of this differential behavior should be taken into account when evaluating light pollution indicator datasets for assessing the outcomes of public policy decisions regarding the upgrading of outdoor lighting systems. |
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0022-4073 |
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GFZ @ kyba @ |
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2810 |
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Author |
Bará, S.; Rodríguez-Arós, Á.; Pérez, M.; Tosar, B.; Lima, R.; Sánchez de Miguel, A.; Zamorano, J. |
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Title |
Estimating the relative contribution of streetlights, vehicles, and residential lighting to the urban night sky brightness |
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Journal Article |
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Year |
2018 |
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Lighting Research & Technology |
Abbreviated Journal |
Lighting Res & Tech |
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October 2018 |
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Remote Sensing; traffic; Roadway lighting |
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Abstract |
Under stable atmospheric conditions the brightness of the urban sky varies throughout the night following the time course of the anthropogenic emissions of light. Different types of artificial light sources (e.g. streetlights, residential, and vehicle lights) have specific time signatures, and this feature makes it possible to estimate the amount of brightness contributed by each of them. Our approach is based on transforming the time representation of the zenithal night sky brightness into a modal expansion in terms of the time signatures of the different sources of light. The modal coefficients, and hence the absolute and relative contributions of each type of source, can be estimated by means of a linear least squares fit. A practical method for determining the time signatures of different contributing sources is also described, based on wide-field time-lapse photometry of the urban nightscape. Our preliminary results suggest that, besides the dominant streetlight contribution, artificial light leaking out of the windows of residential buildings may account for a significant share of the time-varying part of the zenithal night sky brightness at the measurement locations, whilst the contribution of the vehicle lights seems to be significantly smaller. |
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Área de Óptica, Dept. Física Aplicada, Facultade de Óptica e Optometría, Universidade de Santiago de Compostela, Santiago de Compostela 15782, Galicia, Spain. salva.bara(at)usc.es |
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SAGE |
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English |
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English |
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1477-1535 |
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GFZ @ kyba @ |
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2052 |
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Bará, S.; Tapia, C.; Zamorano, J. |
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Title |
Absolute Radiometric Calibration of TESS-W and SQM Night Sky Brightness Sensors |
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Journal Article |
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2019 |
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Sensors |
Abbreviated Journal |
Sensors |
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19 |
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6 |
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1336 |
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Instrumentation; calibration; SQM; TESS; photometer; sky brightness |
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We develop a general optical model and describe the absolute radiometric calibration of the readings provided by two widely-used night sky brightness sensors based on irradiance-to-frequency conversion. The calibration involves the precise determination of the overall spectral sensitivity of the devices and also the constant G relating the output frequency of the light-to-frequency converter chip to the actual band-weighted and field-of-view averaged spectral radiance incident on the detector (brightness). From these parameters, we show how to define a rigorous astronomical absolute photometric system in which the sensor measurements can be reported in units of magnitudes per square arcsecond with precise physical meaning. |
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Departmento Física Aplicada, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain; salva.bara(at)usc.es |
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MDPI |
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English |
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English |
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1424-8220 |
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Call Number |
IDA @ john @ |
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2263 |
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Author |
Bará, S.; Tilve, V.; Nievas, M.; Sanchez de Miguel, A.; Zamorano, J. |
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Title |
Zernike power spectra of clear and cloudy light-polluted urban night skies |
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Journal Article |
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Year |
2015 |
Publication |
Applied Optics |
Abbreviated Journal |
Appl. Opt. |
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54 |
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13 |
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4120-4129 |
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Skyglow; artificial ligh at night; light pollution; Zernike; power spectrum; atmospheric optics; imaging systems; image analysis |
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The Zernike power spectra of the all-sky night brightness distributions of clear and cloudy nights are computed using a modal projection approach. The results obtained in the B, V and R Johnson-Cousins' photometric bands during a one-year campaign of observations at a light-polluted urban site show that these spectra can be described by simple power laws with exponents close to -3 for clear nights and -2 for cloudy ones. The second-moment matrices of the Zernike coefficients show relevant correlations between modes. The multiplicative role of the cloud cover, that contributes to a significant increase of the brightness of the urban night sky in comparison with the values obtained in clear nights, is described in the Zernike space. |
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Area de Optica, Dept. Fisica Aplicada. Facultade de Fisica / Facultade de Optica e OptometrÃa Universidade de Santiago de Compostela Campus Sur, E-15782 Santiago de Compostela, Galicia, Spain; salva.bara@usc.es |
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Optical Society of America |
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English |
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English |
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Call Number |
IDA @ john @ |
Serial |
1156 |
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Author |
Bará, S.; Ulla, A. |
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Title |
Light Pollution in the Galician Atlantic Islands Maritime-Terrestrial National Park 2018 Report |
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Report |
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Year |
2018 |
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Keywords |
Conservation; Spain; Galicia; Europe; national park |
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The Galician Atlantic Islands Maritime-Terrestrial National Park (PNMTIAG), with the exception of the island of Cortegada, still has night skies of acceptable quality. However, the PNMTIAG islands are under strong photic pressures, both internal and external, that hinder the preservation of the basic features of the natural night, and call for an immediate action of all concerned stakeholders |
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USC Tragsa |
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Galician |
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Galician |
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IDA @ john @ |
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2187 |
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