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Author |
Bará, S. |
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Title |
Characterizing the zenithal night sky brightness in large territories: how many samples per square kilometre are needed? |
Type |
Journal Article |
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Year |
2017 |
Publication |
Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
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Volume  |
473 |
Issue |
3 |
Pages |
4164-4173 |
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Keywords |
Instrumentation; atmospheric effects; light pollution; numerical methods; photometry |
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Abstract |
A recurring question arises when trying to characterize, by means of measurements or theoretical calculations, the zenithal night sky brightness throughout a large territory: how many samples per square kilometre are needed? The optimum sampling distance should allow reconstructing, with sufficient accuracy, the continuous zenithal brightness map across the whole region, whilst at the same time avoiding unnecessary and redundant oversampling. This paper attempts to provide some tentative answers to this issue, using two complementary tools: the luminance structure function and the Nyquist–Shannon spatial sampling theorem. The analysis of several regions of the world, based on the data from the New world atlas of artificial night sky brightness, suggests that, as a rule of thumb, about one measurement per square kilometre could be sufficient for determining the zenithal night sky brightness of artificial origin at any point in a region to within ±0.1 magV arcsec–2 (in the root-mean-square sense) of its true value in the Johnson–Cousins V band. The exact reconstruction of the zenithal night sky brightness maps from samples taken at the Nyquist rate seems to be considerably more demanding. |
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Address |
1Departamento de Física Aplicada, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Galicia, Spain; salva.bara(at)usc.es |
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Publisher |
Oxford Academic |
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Language |
English |
Summary Language |
English |
Original Title |
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ISSN |
0035-8711 |
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no |
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Call Number |
IDA @ john @ |
Serial |
2164 |
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Author |
Bará, S.; Falchi, F.; Furgoni, R.; Lima, R.C. |
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Title |
Fast Fourier-transform calculation of artificial night sky brightness maps |
Type |
Journal Article |
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Year |
2020 |
Publication |
Journal of Quantitative Spectroscopy and Radiative Transfer |
Abbreviated Journal |
Journal of Quantitative Spectroscopy and Radiative Transfer |
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Volume |
240 |
Issue |
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Pages |
106658 |
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Keywords |
Skyglow; Light pollution; Atmospheric optics; Photometry; Radiometry; Fourier transforms |
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Abstract |
Light pollution poses a growing threat to optical astronomy, in addition to its detrimental impacts on the natural environment, the intangible heritage of humankind related to the contemplation of the starry sky and, potentially, on human health. The computation of maps showing the spatial distribution of several light pollution related functions (e.g. the anthropogenic zenithal night sky brightness, or the average brightness of the celestial hemisphere) is a key tool for light pollution monitoring and control, providing the scientific rationale for the adoption of informed decisions on public lighting and astronomical site preservation. The calculation of such maps from satellite radiance data for wide regions of the planet with sub-kilometric spatial resolution often implies a huge amount of basic pixel operations, requiring in many cases extremely large computation times. In this paper we show that, using adequate geographical projections, a wide set of light pollution map calculations can be reframed in terms of two-dimensional convolutions that can be easily evaluated using conventional fast Fourier-transform (FFT) algorithms, with typical computation times smaller than 10^-6 s per output pixel. |
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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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Publisher |
Elsevier |
Place of Publication |
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Language |
English |
Summary Language |
English |
Original Title |
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ISSN |
0022-4073 |
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no |
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Call Number |
IDA @ john @ |
Serial |
2782 |
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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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Publisher |
Elsevier |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
English |
Original Title |
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Series Editor |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0022-4073 |
ISBN |
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Notes |
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no |
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Call Number |
IDA @ john @ |
Serial |
2163 |
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Author |
Fiorentin, P.; Boscaro, F. |
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Title |
A method for measuring the light output of video advertising reproduced by LED billboards |
Type |
Journal Article |
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Year |
2019 |
Publication |
Measurement |
Abbreviated Journal |
Measurement |
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Volume |
138 |
Issue |
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Pages |
25-33 |
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Keywords |
Lighting; Energy; Instrumentation; Planning; Light-emitting diode displays; Photometry; Video recording; Image analysis; CCD image sensors; Luminance; Glare |
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Abstract |
Improving knowledge of the light output of digital billboards is important to better assess their effect on driver distraction when they are installed along roads. In this work the emission of an LED based billboard is measured when playing advertising video-clips. In particular the average and the maximum values of the luminance are evaluated. The same video-clips are also analyzed when shown on an LCD monitor, aiming at separating the variability of the videos and of the playing device. The results allow to evaluate an utilization factor of the billboard: the videos have an average luminance around 11% and a peak luminance of 35% of the maximum luminance obtainable from the billboard. The power consumption of the billboard is measured, aside the photometric analysis. The luminance of the device are found linearly dependent on both the power and the effective current absorbed by the device from the grid, with a discrepancy within 6%. It could be a useful information for billboard manufacturers to qualify their product when they do not own photometric instruments. |
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Address |
Department of Industrial Engineering, University of Padova, Padova, Italy; pietro.fiorentin(at)unipd.it |
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Publisher |
Elsevier |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
English |
Original Title |
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Series Editor |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
0263-2241 |
ISBN |
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Notes |
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Approved |
no |
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Call Number |
GFZ @ kyba @ |
Serial |
2214 |
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Author |
Cinzano, P.; Falchi, F. |
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Title |
A portable wide-field instrument for mapping night sky brightness automatically |
Type |
Journal Article |
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Year |
2003 |
Publication |
Memorie della Società Astronomica Italiana |
Abbreviated Journal |
Mem. S.A. It. |
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Volume |
74 |
Issue |
2 |
Pages |
458-459 |
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Keywords |
Instrumentation; all-sky; photometry; sky brightness |
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Abstract |
We present a portable automatic instrument for monitoring night sky brightness and atmospherical transparency in astronomical photometrical bands. Main requirements were: fast and automatic coverage of the entire sky, lightness, transportability and quick set-up in order to take measurements from more sites in the same night, easily available commercial components and software to be reproduced by any interested institution, included amateurs astronomers groups. |
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Address |
Istituto di Scienza e Tecnologia dell’Inquinamento Luminoso, Thiene, Italy |
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Corporate Author |
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Thesis |
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Publisher |
Società Astronomica Italiana |
Place of Publication |
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Editor |
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Language |
English |
Summary Language |
English |
Original Title |
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Series Editor |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1824-016X |
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Notes |
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Call Number |
IDA @ john @ |
Serial |
2243 |
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