Introducing the dark sky unit for multi-spectral measurement of the night sky quality with commercial digital cameras

Kollath, Zoltán; Cool, Andrew; Jechow, Andreas; Kolláth, Kornél; Száz, Dénes; Tong, Kai

doi:10.1016/j.jqsrt.2020.107162

Cited by 35 publications

(51 citation statements)

References 21 publications

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“…The SQM is designed to measure at the zenith and should be used with care in the context of biological studies (Longcore et al ., 2020). There are attempts to establish more intuitive units for the night sky brightness like the ‘natural sky unit’ and the ‘dark sky unit’ (see Kolláth et al ., 2020), but so far none of them has been standardised.…”

Section: Brief Overview Of Light Measurement Basicsmentioning

confidence: 99%

Assessing long‐term effects of artificial light at night on insects: what is missing and how to get there

Kalinkat

Grubisić

Jechow

et al. 2021

Insect Conserv Diversity

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1. Widespread and significant declines of insect population abundances and biomass are currently one of the most pressing issues in entomology, ecology and conservation biology. It has been suggested that artificial light at night is one major driver behind this trend.2. Recent advances in the gathering and analysis of long-term data sets of insect population and biomass trends, however, have mostly focused on the effects of climate change and agricultural intensification.3. We posit here that adequate assessment of artificial night at light that would be required to evaluate its role as a driver of insect declines is far from trivial. Currently its implementation into entomological monitoring programmes and long-running ecological experiments is hampered by several challenges that arise due to (i) its relatively late appearance as a biodiversity threat on the research agenda and (ii) the interdisciplinary nature of the research field where biologists, physicists and engineers still need to develop a set of standardised assessment methods that are both biologically meaningful and easy to implement.4. As more studies that address these challenges are urgently needed, this article aims to provide a short overview of the few existing studies that have attempted to investigate longer-term effects of artificial light at night on insect populations. 5. To improve the quality and relevance of studies addressing artificial light at night and its effect on insects, we present a set of best practise recommendations where this field needs to be heading in the coming years and how to achieve it.

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Section: Brief Overview Of Light Measurement Basicsmentioning

confidence: 99%

Assessing long‐term effects of artificial light at night on insects: what is missing and how to get there

Kalinkat

Grubisić

Jechow

et al. 2021

Insect Conserv Diversity

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“…Unfortunately, some of these metrics were not well defined, and most of them did not follow the requirements of SI traceability. To eliminate these problems, Kolláth et al (2020) provided a recommendation for a new unit. The definition is based on spectroradiometry, and it can be directly applied for digital camera measurements.…”

Section: Evaluation Of the Measurementsmentioning

confidence: 99%

Light Pollution Survey in Hungarian National Parks

Kollath¹,

Száz²,

Tong³

et al. 2021

Acta Universitatis de Carolo Eszterházy Nominatae. Sectio Biolo

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We have started a light pollution survey in the Hungarian national parks. We use a mobile laboratory consisting of digital cameras and robotic panorama heads to gather high-resolution panorama imaging radiometry. The same type of cameras with fish-eye lenses are used in fix monitoring stations. Parallel to the imaging radiometry, we measure the spectral distribution of the sky radiation. The spectroradiometry provides additional calibration check on the measurements and further information on the sources of light. The mobile laboratory provides an excellent spatial resolution at a given national park while the monitoring all-sky camera stations add the possibility to detect temporal changes in night sky quality. We developed new SI traceable metrics for the measurement of night sky quality. The RGB colour channels of the camera provide an optimal way to obtain multispectral radiance information. The selected metric is the band-averaged spectral radiance. Besides, we use a colour enhancement technique to find traces of different sources of night sky radiance. In the near future, we expect a large amount of high-quality data from the Hungarian national parks, which provide an outstanding possibility in light pollution related and atmospheric research. In the paper, we present the first results of the sky quality survey.

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“…This drawback can be solved without changing our device if we rotate the camera by 90 degrees and take two or multiple fish-eye images in the vertical plane [ 22 ]. The best way to achieve the highest precision and resolution at dark locations and under clear sky conditions is to use a robotic panorama head with a 24 mm or 35 mm rectilinear lens on a full-frame digital camera [ 23 ]. With this set-up, 28 individual images are enough to cover the whole sky and some of the ground and environment with high spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

“…Because of the short exposure time, the movement artefacts (like star trails) caused by the apparent rotation of the sky do not disturb the measurement. Astrometry-based corrections of the images can also be made during post-processing [ 23 ].…”

Section: Introductionmentioning

confidence: 99%

“…DSLR cameras are calibrated by astronomical or standard CIE photometry [ 24 ]. Previously, we have suggested a measurement method that is based on the calibration of DSLR cameras with known narrow-band light sources and a spectroradiometer with which the natural sky spectrum could be precisely determined [ 23 ]. We introduced the dark sky unit (dsu), which is a new SI-traceable unit (nW/m

/sr/nm) for measuring sky brightness and it can be separately determined for the three colour channels of the digital camera.…”

Section: Introductionmentioning

confidence: 99%

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The Colour of the Night Sky

et al. 2020

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The measurement of night sky quality has become an important task in night sky conservation. Modern measurement techniques involve mainly a calibrated digital camera or a spectroradiometer. However, panchromatic devices are still prevalent to this day, even in the absence of determining the spectral information of the night sky. In the case of multispectral measurements, colour information is currently presented in multiple ways. One of the most frequently used metrics is correlated colour temperature (CCT), which is not without its limitation for the purpose of describing especially the colour of natural night sky. Moreover, visually displaying the colour of the night sky in a quantitatively meaningful way has not attracted sufficient attention in the community of astronomy and light pollution research—most photographs of the night sky are post-processed in a way for aesthetic attractiveness rather than accurate representation of the night sky. The spectrum of the natural night sky varies in a wide range depending on solar activity and atmospheric properties. The most noticeable variation in the visible range is the variation of the atomic emission lines, primarily the green oxygen and orange sodium emission. Based on the accepted models of night sky emission, we created a random spectral database which represents the possible range of night sky radiance distribution. We used this spectral database as a learning set, to create a colour transformation between different colour spaces. The spectral sensitivity of some digital cameras is also used to determine an optimal transformation matrix from camera defined coordinates to real colours. The theoretical predictions were extended with actual spectral measurements in order to test the models and check the local constituents of night sky radiance. Here, we present an extended modelling of night sky colour and recommendations of its consistent measurement, as well as methods of visualising the colour of night sky in a consistent way, namely using the false colour enhancement.

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Introducing the dark sky unit for multi-spectral measurement of the night sky quality with commercial digital cameras

Cited by 35 publications

References 21 publications

Assessing long‐term effects of artificial light at night on insects: what is missing and how to get there

Assessing long‐term effects of artificial light at night on insects: what is missing and how to get there

Light Pollution Survey in Hungarian National Parks

The Colour of the Night Sky

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