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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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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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2586-1247 |
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Call Number |
IDA @ john @ |
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2162 |
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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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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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Oxford Academic |
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English |
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English |
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0035-8711 |
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IDA @ john @ |
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2164 |
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Author |
Bará, S. |
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Title |
Black-body luminance and magnitudes per square arcsecond in the Johnson-Cousins BVR photometric bands |
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Journal Article |
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Year |
2019 |
Publication |
Photonics Letters of Poland |
Abbreviated Journal |
Photon. Lett. Pl. |
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Volume |
11 |
Issue |
3 |
Pages |
63 |
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Keywords |
Skyglow; night sky brightness; luminance; photometric |
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Abstract |
A relevant amount of light pollution studies deal with the unwanted visual effects of artificial light at night, including the anthropogenic luminance of the sky that hinders the observation of the celestial bodies which are a main target of ground-based astrophysical research, and a key asset of the intangible heritage of humankind. Most quantitative measurements and numerical models, however, evaluate the anthropogenic sky radiance in any of the standard Johnson-Cousins UBVRI photometric bands, generally in the V one. Since the Johnson-Cousins V band is not identical with the visual CIE V-lambda used to assess luminance, the conversion between these two photometric systems turns out to be spectrum-dependent. Given its interest for practical applications, in this Letter we provide the framework to perform this conversion and the transformation constants for black-body spectra of different absolute temperatures. |
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Dept. Física Aplicada, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia |
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Photonics Society of Poland |
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English |
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English |
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2080-2242 |
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no |
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Call Number |
IDA @ john @ |
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2685 |
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Author |
Bará, S., Lima, R.C. |
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Title |
Photons without borders: quantifying light pollution transfer between territories |
Type |
Journal Article |
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Year |
2018 |
Publication |
International Journal of Sustainable Lighting |
Abbreviated Journal |
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Volume |
20 |
Issue |
2 |
Pages |
51-61 |
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Keywords |
Skyglow |
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Abstract |
The light pollution levels experienced at any given site generally depend on a wide number of artificial light sources distributed throughout the surrounding territory. Since photons can travel long distances before being scattered by the atmosphere, any effective proposal for reducing local light pollution levels needs an accurate assessment of the relative weight of all intervening light sources, including those located tens or even hundreds of km away. In this paper we describe several ways of quantifying and visualizing these relative weights. Particular emphasis is made on the aggregate contribution of the municipalities, which are -in many regions of the world- the administrative bodies primarily responsible for the planning and maintenance of public outdoor lighting systems. |
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NC @ ehyde3 @ |
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2066 |
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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 |
Publication |
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Keywords |
Conservation; Spain; Galicia; Europe; national park |
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Abstract |
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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