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Author |
Wallner, S.; Kocifaj, M.; Komar, L.; Solano-Lamphar, H.A. |
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Title |
Night-sky imaging as a potential tool for characterization of total lumen output from small and medium-sized cities |
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Journal Article |
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2020 |
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Monthly Notices of the Royal Astronomical Society |
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494 |
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4 |
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5008-5017 |
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Skyglow |
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In this article, the asymptotic formula developed in past work and applied to predict skyglow due to distant sources was evolved, with the objective of characterizing small and medium-sized cities in the observer's surroundings. To enable this, a combination of theoretical computations and in situ measurements is needed, aiming to distinguish between dominant and smaller light-emitting sources, with the latter usually being camouflaged when measuring the night sky. Furthermore, for numerical modelling of skyglow, few of the most important parameters, specifically the amount of total lumens installed and radiated to the upward hemisphere, can be derived. Astronomical observatories, in particular, can profit from this concept, since they are usually situated far away from large cities but can still be surrounded by smaller villages and towns. We present a detailed description of how theoretical computations are combined with all-sky photometry in order to obtain the properties mentioned. Results are compared with satellite data, showing that, regarding approximations undertaken for processing, they are comparable, underlining the functionality of our approach. The idea of including in situ observations enables us to quantify the impact of small and medium-sized cities globally and independent of location, as long as measurements were conducted outside light domes. In addition, the presented work may be of major interest to the light-pollution community if conducting long-term observations of cities, since the quality of commonly used satellite data is going to decrease in the future, due to blindness in short wavelengths and upcoming conversions of public lighting systems to blue-enlightened LEDs. |
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0035-8711 |
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GFZ @ kyba @ |
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2911 |
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Bará, S.; Aubé, M.; Barentine, J.; Zamorano, J. |
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Title |
Magnitude to luminance conversions and visual brightness of the night sky |
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Journal Article |
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2020 |
Publication |
Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
MNRAS |
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493 |
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2 |
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2429–2437 |
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Skyglow; light pollution; atmospheric effects; techniques: photometric; methods: numerical; luminance |
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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 (mV, 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 mV = 0.00 mpsas is found to vary between 1.11–1.34 × 105 cd m−2 if mV is reported in the absolute (AB) magnitude scale, and between 1.18–1.43 × 105 cd m−2 if a Vega scale for mV is used instead. The photopic luminance for mV = 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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Departamento de Física Aplicada, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia; salva.bara(at)usc.gal |
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Oxford Academic |
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IDA @ john @ |
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2825 |
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Cavazzani, S.; Ortolani, S.; Bertolo, A.; Binotto, R.; Fiorentin, P.; Carraro, G.; Saviane, I.; Zitelli, V. |
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Title |
Sky Quality Meter and satellite correlation for night cloud-cover analysis at astronomical sites |
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Journal Article |
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2020 |
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Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
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493 |
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2 |
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2463-2471 |
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Skyglow |
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The analysis of night cloud cover is very important for astronomical observations in real time, considering a typical observation time of about 15 minutes, and to provide statistics. In this article, we use the Sky Quality Meter (SQM) for high-resolution temporal analysis of the La Silla and Asiago (Ekar Observatory) sky: 3 and 5 minutes respectively. We investigate the annual temporal evolution of the natural contributions of the sky at a site not influenced by artificial light at night (ALAN) and at one highly influenced. We also make a correlation between GOES and Aqua satellite data and ground-based SQM data to confirm the relationship between the SQM data and cloud cover. We develop an algorithm that allows the use of the SQM for night cloud detection and reach correlations with the nighttime cloud cover detected by the GOES and Aqua satellites of 97.2 per cent at La Silla and 94.6 per cent at Asiago. Our algorithm also classifies photometric (PN) and spectroscopic nights (SN). We measure 59.1 per cent PN and 21.7 per cent SN for a total percentage of clear nights of 80.8 per cent at La Silla in 2018. The respective Ekar Observatory values are 31.1 per cent PN, 24.0 per cent SN and 55.1 per cent of total clear night time. Application to the SQM network would involve the development of long-term statistics and large data forecasting models for site testing and real-time astronomical observation. |
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0035-8711 |
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GFZ @ kyba @ |
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2842 |
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Puschnig, J.; Wallner, S.; Posch, T. |
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Circalunar variations of the night sky brightness – an FFT perspective on the impact of light pollution |
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Journal Article |
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2020 |
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Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
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492 |
Issue |
2 |
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2622-2637 |
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Keywords |
Skyglow; Moonlight |
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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 2-yr 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 magSQMarcsec−2 and the amplitude of the circalunar signal is found, indicating that for sites with a mean zenithal NSB brighter than 16.5 magSQMarcsec−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 19 in the state capital of Linz (∼200 000 inhabitants) and 13 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. |
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GFZ @ kyba @ |
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2838 |
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Author |
Simoneau, A.; Aubé, M.; Bertolo, A. |
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Multispectral analysis of the night sky brightness and its origin for the Asiago Observatory, Italy |
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Journal Article |
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2020 |
Publication |
Monthly Notices of the Royal Astronomical Society |
Abbreviated Journal |
MNRAS |
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Volume |
491 |
Issue |
3 |
Pages |
4398-4405 |
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Skyglow; light pollution; numerical methods; Site testing; Italy; Observatories |
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Night protection has been a major concern for astronomers since the electrification of cities and is beginning to be recognized as a major environmental problem. In recent years, regulations have been put in place through the establishment of Dark Sky Reserves that impose stringent constraints on lighting practices for cities in protected areas. Astronomers from the Asiago Observatory, located in the Veneto region of Italy, would like to create an area of this nature around their facilities to improve and protect the quality of their astronomical observations. This study assesses the current state of the sky in the region through numerical modelling using the latest improvements to the ILLUMINA model and aims to identify the main contributing sources of artificial light. The explicit calculation of the contribution of private residential lighting helps to discern the origin of the light. We also present a new approach for extracting an estimate of the distribution of lamp technology in a region from images taken from the International Space Station. |
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Bishop’s University, 2600 rue College, Sherbrooke, Québec J1M 1Z7, Canada; alsimoneau(at)gmail.com |
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Oxford Academic |
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English |
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0035-8711 |
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IDA @ john @ |
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2790 |
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