Variations on a classical theme: On the formal relationship between magnitudes per square arcsecond and luminance

Bará, Salvador

doi:10.26607/ijsl.v19i2.77

Cited by 13 publications

(14 citation statements)

References 33 publications

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“…Note that for any given photometric band ( ) with a well specified reference radiance ( ), the first and third factors of equation (8) are constant, whereas the second one (the ratio of the V(λ) to S in-band radiances) depends on the spectral composition of the incident light, ( ). Only in the very particular case when the photometric band ( ) strictly coincides with the CIE visual one, V(λ), the second factor equals 1, and 0 turns out to be independent from the spectrum of the light (Bará, 2017). Then, the zero-point luminance 0 that determines the S-band mpsas to cd m -2 conversion is not a single value but must be calculated for each ( ) on a case by case basis.…”

Section: Transforming Magnitudes Per Square Arcsecond To Luminancesmentioning

confidence: 99%

“…In previous works we developed a consistent definition of an absolute mpsas system for the human visual system (Bará, 2017), and reported the conversion factors for determining the luminance of blackbody radiation of arbitrary temperature as a function of its mpsas brightness in the Johnson-Cousins B, V, and R photometric bands (Bará, 2019).…”

Section: Introductionmentioning

confidence: 99%

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Magnitude to luminance conversions and visual brightness of the night sky

Bará

Aubé

Barentine

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The visual brightness of the night sky is not a single-valued function of its brightness in other photometric bands, because the transformations between photometric systems depend on the spectral power distribution of the skyglow. We analyze the transformation between the night sky brightness in the Johnson-Cousins V band (m V , measured in magnitudes per square arcsecond, mpsas) and its visual luminance (L, in SI units cd m -2 ) for observers with photopic and scotopic adaptation, in terms of the spectral power distribution of the incident light. We calculate the zero-point luminances for a set of skyglow spectra recorded at different places in the world, including strongly light-polluted locations and sites with nearly pristine natural dark skies. The photopic skyglow luminance corresponding to m V =0.00 mpsas is found to vary between 1.11-1.34 x 10 5 cd m -2 if m V is reported in the absolute (AB) magnitude scale, and between 1.18-1.43 x 10 5 cd m -2 if a Vega scale for m V is used instead. The photopic luminance for m V =22.0 mpsas is correspondingly comprised between 176 and 213 µcd m -2 (AB), or 187 and 227 µcd m -2 (Vega). These constants tend to decrease for increasing correlated color temperatures (CCT). The photopic zero-point luminances are generally higher than the ones expected for blackbody radiation of comparable CCT. The scotopic-to-photopic luminance ratio (S/P) for our spectral dataset varies from 0.8 to 2.5. Under scotopic adaptation the dependence of the zero-point luminances with the CCT, and their values relative to blackbody radiation, are reversed with respect to photopic ones.

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Section: Transforming Magnitudes Per Square Arcsecond To Luminancesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Magnitude to luminance conversions and visual brightness of the night sky

Bará

Aubé

Barentine

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…To that end we resorted to the measurements recorded by the SQM-LE sensor run by the Servei Català per la Prevenció de la Contaminació Acústica i Lumínica de la respectively. Note that this introduces some error if the results are interpreted as true luminances in cd/m 2 , because the SQM and V photometric bands are not exactly the same [49][50]. The natural sky luminance was then subtracted from the total one recorded from the ship at each point of the route, allowing us to estimate the value of the artificial component as…”

Section: Predicted Sky Brightness and Data Processingmentioning

confidence: 99%

Light pollution offshore: Zenithal sky glow measurements in the mediterranean coastal waters

Ges

Bará

García-Gil

et al. 2018

Journal of Quantitative Spectroscopy and Radiative Transfer

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Light pollution is a worldwide phenomenon whose consequences for the natural environment and the human health are being intensively studied nowadays. Most published studies address issues related to light pollution inland. Coastal waters, however, are spaces of high environmental interest, due to their biodiversity richness and their economical significance. The elevated population density in coastal regions is accompanied by correspondingly large emissions of artificial light at night, whose role as an environmental stressor is increasingly being recognized. Characterizing the light pollution levels in coastal waters is a necessary step for protecting these areas. At the same time, the marine surface environment provides a stage free from obstacles for measuring the dependence of the skyglow on the distance to the light polluting sources, and validating (or rejecting) atmospheric light propagation models. In this work we present a proof-of-concept of a gimbal measurement system that can be used for zenithal skyglow measurements on board both small boats and large vessels under actual navigation conditions. We report the results obtained in the summer of 2016 along two measurement routes in the Mediterranean waters offshore Barcelona, travelling 9 and 31.7 km away from the coast. The atmospheric conditions in both routes were different from the ones assumed for the calculation of recently published models of the anthropogenic sky brightness. They were closer in the first route, whose results approach better the theoretical predictions. The results obtained in the second route, conducted under a clearer atmosphere, showed systematic differences that can be traced back to two expected phenomena, which are a consequence of the smaller aerosol content: the reduction of the anthropogenic sky glow at short distances from the sources, and the slower decay rate of brightness with distance, which gives rise to a relative excess of brightness at large distances from the coastline.

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“…We do so using two models. The first one, describing the lunar (Bará, 2016(Bará, , 2017, using Equation 1. Despite the fact that this formula is widely used to estimate luminances from SQM magnitudes, it was originally derived by Garstang (1986) for Johnson V-band magnitudes, and is thus just an approximation.…”

Section: Synthetic Models Of Ground Illumination By the Moon And Totamentioning

confidence: 99%

Circalunar variations of the night sky brightness – an FFT perspective on the impact of light pollution

Puschnig

Wallner

Posch

2019

Monthly Notices of the Royal Astronomical Society

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Circa-monthly activity conducted by moonlight is observed in many species on Earth. Given the vast amount of artificial light at night (ALAN) that pollutes large areas around the globe, the synchronization to the circalunar cycle is often strongly perturbed. Using two-year data from a network of 23 photometers (Sky Quality Meters; SQM) in Austria (latitude ∼48°), we quantify how light pollution impacts the recognition of the circalunar periodicity. We do so via frequency analysis of nightly mean sky brightnesses using Fast Fourier Transforms. A very tight linear relation between the mean zenithal night sky brightness (NSB) given in mag SQM arcsec −2 and the amplitude of the circalunar signal is found, indicating that for sites with a mean zenithal NSB brighter than 16.5 mag SQM arcsec −2 the lunar rhythm practically vanishes. This finding implies that the circalunar rhythm is still detectable (within the broad bandpass of the SQM) at most places around the globe, but its amplitude against the light polluted sky is strongly reduced. We find that the circalunar contrast in zenith is reduced compared to ALAN-free sites by factors of 1 /9 in the state capital of Linz (∼200,000 inhabitants) and 1 /3 in small towns, e.g. Freistadt and Mattighofen, with less than 10,000 inhabitants. Only two of our sites, both situated in national parks (Bodinggraben and Zöblboden), show natural circalunar amplitudes. At our urban sites we further detect a strong seasonal signal that is linked to the amplification of anthropogenic skyglow during the winter months due to climatological conditions. Impact of moonlight on animals, plants and humansThe Moon's synodic period of 29.5 days is its orbital time around the Earth required to show the exact same lunar phase, i.e. for example the time span between two consecutive full moons. The corresponding circalunar oscillation of the Moon's illumination impacts many types of life on Earth, in particular in the context of reproduction cycles. Scientific work on this topic dates back to the early 20 th century (e.g. Fox and Gardiner (1924)) and it was likely already recognized by fishermen in the antiquity -due to practical implications -that the size of (edible) gonads of sea urchins varies over the lunar month (Raible et al., 2017).

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Variations on a classical theme: On the formal relationship between magnitudes per square arcsecond and luminance

Cited by 13 publications

References 33 publications

Magnitude to luminance conversions and visual brightness of the night sky

Magnitude to luminance conversions and visual brightness of the night sky

Light pollution offshore: Zenithal sky glow measurements in the mediterranean coastal waters

Circalunar variations of the night sky brightness – an FFT perspective on the impact of light pollution

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