Abstract: We present here observations of the polarisation of four auroral lines in the auroral oval and in the polar cusp using a new ground polarimeter called Petit Cru. Our results confirm the already known polarisation of the red line, and show for the first time that the three other lines observed here (namely 557.7 nm, 391.4 nm and 427.8 nm) are polarised as well up to a few percent. We show that in several circumstances, this polarisation is linked to the local magnetic activity and to the state of the ionosphere through the electron density measured with EISCAT. However, we also show that the contribution of light pollution from nearby cities via scattering can not be ignored and can play an important role in polarisation measurements. This series of observations questions the geophysical origin of the polarisation. It also leaves open its relation to the magnetic field orientation and to the state of both the upper atmosphere and the troposphere.
Keywords: Skyglow; Polarization; Aurora
Abstract: Accelerating coastal development is increasing the exposure of marine ecosystems to nighttime light pollution, but is anthropogenic light reaching the seafloor in sufficient quantities to have ecological impacts? Using a combination of mapping, and radiative transfer modelling utilising in situ measurements of optical seawater properties, we quantified artificial light exposure at the sea surface, beneath the sea surface, and at the sea floor of an urbanised temperate estuary bordered by an LED lit city. Up to 76% of the three-dimensional seafloor area was exposed to biologically important light pollution. Exposure to green wavelengths was highest, while exposure to red wavelengths was nominal. We conclude that light pollution from coastal cities is likely having deleterious impacts on seafloor ecosystems which provide vital ecosystem services. A comprehensive understanding of these impacts is urgently needed.
Keywords: Ecology; Skyglow; Remote Sensing
Abstract: Light pollution generated by the excessive use of artificial light at night is an environmental and ecological concern. Artificial light at night is diffused far from the sources, for long distances by scattering in the atmosphere (skyglow), thus affecting the night sky and the biodiversity of rural and natural areas. The characterization of the level and variability of light pollution has become an important issue for several disciplines.
This study analyzes light pollution in urban, rural and remote sites in Tuscany (Italy) by monitoring night sky brightness. Night sky brightness (NSB) data collected from 2016 to 2019 were analyzed to assess annual and seasonal variability at each site and between sites. The relationship between night sky brightness and moonlight and weather conditions were also analyzed. Trend analysis was also performed to evaluate the degradation of the quality of the measurement with time due to dirty accumulation on the sensor shield.
NSB in Tuscany during moonless nights ranged between 17.3 and 21.8 mpsas. The monthly cycle of moonlight is the main driver of night sky brightness variability in the remote site (21.8 mpsas on moonless nights and 18.5 mpsas on full moon nights) with a slight, but significant darkening effect during rainy conditions (22.3 mpsas). In urban sites, moonlight cycle is almost completely masked by weather conditions, as it can be seen from the analysis of seasonal variability, lunar monthly cycle analysis and weather condition analysis. Average night sky brightness on rainy days might reach 15.4 mpsas (approximately 436 times brighter than the natural background), an intensity that is even higher than average night sky brightness in full moonlight at the same site (16.6 mpsas). Light pollution can reach levels that might affect nocturnal species, and therefore the study of long term variability of light pollution is important for ecological studies.
This study analyzes light pollution in urban, rural and remote sites in Tuscany (Italy) by monitoring night sky brightness. Night sky brightness (NSB) data collected from 2016 to 2019 were analyzed to assess annual and seasonal variability at each site and between sites. The relationship between night sky brightness and moonlight and weather conditions were also analyzed. Trend analysis was also performed to evaluate the degradation of the quality of the measurement with time due to dirty accumulation on the sensor shield.
NSB in Tuscany during moonless nights ranged between 17.3 and 21.8 mpsas. The monthly cycle of moonlight is the main driver of night sky brightness variability in the remote site (21.8 mpsas on moonless nights and 18.5 mpsas on full moon nights) with a slight, but significant darkening effect during rainy conditions (22.3 mpsas). In urban sites, moonlight cycle is almost completely masked by weather conditions, as it can be seen from the analysis of seasonal variability, lunar monthly cycle analysis and weather condition analysis. Average night sky brightness on rainy days might reach 15.4 mpsas (approximately 436 times brighter than the natural background), an intensity that is even higher than average night sky brightness in full moonlight at the same site (16.6 mpsas). Light pollution can reach levels that might affect nocturnal species, and therefore the study of long term variability of light pollution is important for ecological studies.
Keywords: Skyglow
Abstract: This work presents the possibility of using the extremely popular compact digital cameras of smartphones or action cameras to perform sky photometry. The newest generation of these devices allows to save raw images. They are not as good as digital single-lens reflex camera, in particular in terms of sensitivity, noise and pixel depth (10 bit versus 12 bit or more), but they have the advantage of being extremely widespread on the population and relatively cheap. These economical digital compact cameras work with an electronic shutter, it overcomes the consumption of mechanics and allows to gather images for long time. The work uses a simple calibration method to transfer raw data from the proprietary RGB color space to the standard CIE 1931 color space. It allows the measurement of sky luminance in cd m−2 with an expected uncertainty of about 20%. Furthermore, the colorimetric calibration allows to know the correlated color temperature of a portion of the sky, it can help the identification of the kind of polluting sources. Aiming at better clarifying the performances of calibrated digital compact cameras, a comparison with a calibrated DSLR camera is presented in outdoor situations showing a good agreement both for luminance and color temperature measurements.
Keywords: Skyglow; Instrumentation
Abstract: Künstliches Licht kann als eine der größten technischen Errungenschaften der Menschheit angesehen werden, die erhebliche Veränderungen bzw. Fortschritte der Arbeits- und Lebensweisen ermöglichen. Mit künstlicher Beleuchtung wird aber auch der natürliche Rhythmus von Tag und Nacht verändert und damit das Gesamtgefüge des Naturhaushaltes und der Nachtlandschaft transformiert. Ein natürlich dunkler Nachthimmel ist in Deutschland selten geworden. Licht-glocken über urbanen Gebieten sind weit weg von ihrem Entstehungsort in unbeleuchteten Gebieten noch sichtbar und lassen Sterne und die Milchstraße unkenntlich werden. Nicht nur das direkte elektrische Licht erleuchtet unsere Umwelt, sondern auch der nach oben abgestrahlte und reflektierte Teil des Lichts. Schichten der Atmosphäre, Staub oder Wassertropfen reflektieren und streuen das Licht. Dieser auch als Skyglow bezeichnete Effekt bewirkt eine zusätzliche Erhellung. Neben dieser künstlich erhöhten Himmelshelligkeit kann Licht auch die direkte Umgebung ungewollt aufhellen oder durch Blendung das Sehen einschränken. Licht ist ein wichtiger externer Zeitgeber für die innere Uhr der Lebewesen, an dessen natürlichen Rhythmus sich Menschen, Tiere und Pflanzen über Jahrhunderte angepasst haben. So wird vermutet, dass die permanent und periodisch veränderten Lichtverhältnisse durch zunehmende künstliche Beleuchtung negative Auswirkungen auf die menschliche Gesundheit haben und ebenso zu ökologischen Beeinträchtigungen führen.All diese nichtintendierten Wirkungen der künstlichen Beleuchtung werden unter dem Sammelbegriff Lichtverschmutzung verstanden. Lichtverschmutzung ist hier definiert als unerwünschte Wirkung künstlicher Beleuchtung im Außenbereich, also das Licht, das räumlich (Richtung und Fläche), zeitlich (Tages- und Jahreszeit, Dauer, Periodizität) oder in der Intensität oder spektralen Zusammensetzung (z.B. Ultraviolett- oder Blauanteil) über den reinen Beleuchtungszweck hinaus nicht beabsichtigte Auswirkungen hat (Kuechly et al. 2018). Mit dem vorliegenden Bericht werden der wissenschaftliche Erkenntnis-stand im Hinblick auf Umfang und Trends der Lichtverschmutzung sowie ihre wirtschaftlichen und soziokulturellen, humanmedizinischen und ökologischen Wirkungen zusammengefasst. Auf Basis dieser Erkenntnisse und aktueller beleuchtungstechnologischer und lichtplanerischer Möglichkeiten werden Handlungsoptionen abgeleitet, die eine Verringerung der Lichtverschmutzung bei gleichzeitiger Berücksichtigung der nutzbringenden Ziele der Beleuchtung unterstützen können.
Keywords: Review; Skyglow; Ecology; Human Health; Lighting; Public Safety; Remote Sensing