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A total lunar eclipse is plausible to have an influence on the variation of some environmental physical parameters, specifically on the conditions of the sky brightness, humidity and temperature. During the eclipse on 14$^{th}$-15$^{th}$ April 2014, these parameters were measured through a photometer and a weather station. The obtained results allow the comparison, practically, of the optimal conditions for observational astronomy work in the Tatacoa desert and therefore to certify it as suitable perfect place to develop night sky astronomical observations. This investigation determined, to some extent, the suitability of this place to carry out astronomical work and research within the optical range. Thus, the changes recorded during the astronomical phenomenon allowed the classification of the sky based on the Bortle Scale, Comment: 14 pages, 7 figures, 4 tables. Accepted for publication in Revista Mexicana de Astronom\'ia y Astrof\'isica (Rev. Mex. Astron. Astrof\'is)

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.

Nowadays most of us do not look at the sky. Nevertheless, most people know “what star sign they belong to”. And yet the vast majority of people do not know what “belonging to a zodiac sign” actually means and have never seen their “sign” in the night sky. Indeed, hardly anyone ever glances at more than a few stars at night– for most people the issue simply never arises.

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 x 10^5 cd m^-2 if mV 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 mV is used instead. The photopic luminance for mV=22.0 mpsas is correspondingly comprised between 176 and 213 microcd m^-2 (AB), or 187 and 227 microcd 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., Comment: Version accepted for publication in Monthly Notices of the Royal Astronomical Society (2020). 5 figures, 1 table, 17 pages. Some misprints corrected in the web abstract

Long-term monitoring of the evolution of the artificial night sky brightness is a key tool for developing science-informed public policies and assessing the efficacy of light pollution mitigation measures. Detecting the underlying artificial brightness trend is a challenging task, since the typical night sky brightness signal shows a large variability with characteristic time scales ranging from seconds to years. In order to effectively isolate the weak signature of the effect of interest, determining the potential long term drifts of the radiance sensing systems is crucial. If these drifts can be adequately characterized, the raw measurements could be easily corrected for them and transformed to a consistent scale. In this short note we report on the progressive darkening of the signal recorded by SQM detectors belonging to several monitoring networks, permanently installed outdoors for periods ranging from several months to several years. The sensitivity drifts were estimated by means of parallel measurements made at the beginning and at the end of the evaluation periods using reference detectors of the same kind that were little or no exposed to weathering in the intervening time. Our preliminary results suggest that SQM detectors installed outdoors steadily increase their readings at an average rate of +0.034 magSQM/arcsec^2 per MWh/m^2 of exposure to solar horizontal global irradiation, that for our locations translates into approximately +0.05 to +0.06 magSQM/arcsec^2 per year., Comment: 5 pages, 1 figure. ArXiv identifier added, some minor misprints corrected

The article presents the results of the studies concerning the influence of a light source installed in luminaire of opal sphere type on the light pollution effect of the night sky. It is known from literature reports that the effect of light pollution is influenced by the spectral distribution of light. Although the influence of the spectral distribution has been widely studied from different perspectives, there is still a need to study this phenomenon—for example, from the point of view of the spectral reflection properties of the ground, on which the lanterns are installed. Hence, the above-mentioned aspect was considered in the authors’ investigations. The luminaire considered has been equipped with 20 different light sources, including the latest generation of lamps (light-emitting diodes, LEDs) as well as the conventional ones. With respect to these light sources, the measurements of light distribution and spectral distribution of emitted radiation of the luminaire were performed. Having these measurement data, the simulations were carried out using the DIALux software, and the calculations were made using the specially prepared calculation tool. On the basis of the results obtained in this way this was stated that the type of light source installed in the luminaire has a significant effect on the sky glow. An important factor affecting light pollution is not only the value of the luminous flux emitted upward but also the spectral characteristics of the emitted radiation, the impact of which is most noticeable. The conclusions from the studies indicate the next steps in the analysis of the light pollution effect. These steps will be focused on extended analysis of LEDs as modern and developed light sources.

Artificial lighting allows for a variety of activities to take place in the absence of sunlight, but also has an increasingly recognized range of negative social and health-related effects. For studies of urban ambient light at night (ALN), objective and standardized data on the amount of ALN experienced by people is often unavailable at the necessary intra-urban spatial scale. In this paper, we outline options for producing such data through (1) field observations acquired with a luminance meter mounted on a vehicle, (2) a 1-m resolution image mosaic produced from a dedicated aerial survey, and (3) a 50-m resolution image taken from the International Space Station. We produce two remote sensing-derived maps of ALN for a large urban area in Canada, and compare their spatial detail to the World Atlas of Artificial Night Sky Brightness, a publicly available alternative data source. Convergent validity with field observations suggests that both mapping approaches can be used to quantify the amount of light humans are exposed to at night, at different locations across a large urban area, and may thus aid in further studying the varied effects of artificial nighttime lighting.

This paper deals with the errors and uncertainties in skyglow measurements caused by the variation of sky's spectrum. It considers the theoretical spectral response of common instruments that are used for light pollution assessment. Various types of light sources were used in this investigation. This study calculates the spectral mismatch errors and the corresponding correction factors for each combination of instrument and light source. The calculation method is described and the results are presented in multiple figures. Calculated data show a big variation in potential errors that can be introduced when comparing readings of diverse instruments without considering the variation of sky's spectrum. This makes the spectral data of the sky a mandatory input to the dark sky assessment. Useful conclusions, related to instruments with better or worse behaviour, are derived from the calculations. The paper also includes suggestions on how to conduct multi-instrument measurements with or without spectral data.

The work continues the research started in 2017. In 2018 in addition to constant monitoring of the night sky glow, a series of experiments were carried out to register fast variations in the spatial intensity distribution of the night sky radiation in the spectral range of 400–900 nm by an optical instruments complex. The devices complex includes: A photometer assembled on the basis of SONY ICX285AL CCD matrix and a high-aperture lens Jupiter 3; Highly sensitive optical system created on the basis of the 3rd generation EPM102G-04-22C electron-optical converter (EOC) and the Baumer HXG40NIR camera based on CMOSIS CMV4000 1 matrix; Fast four-channel photometer with sensors based on silicon photomultipliers. The paper presents the results of experiments on the synchronous observation of fast optical phenomena in the Earth’s atmosphere. The number of events recorded simultaneously on multiple devices is given. We describe methods and algorithms for extracting events from data series.

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 $\mathrm {mag_{SQM}\, arcsec^{-2}}$ and the amplitude of the circalunar signal is found, indicating that for sites with a mean zenithal NSB brighter than 16.5 $\mathrm {mag_{SQM}\, arcsec^{-2}}$ 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 $\frac{1}{9}$ in the state capital of Linz (∼200 000 inhabitants) and $\frac{1}{3}$ 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.

Stars are ubiquitous; the Sun and Moon are singletons. The Sun and the Moon visually dominate the sky. They change in the amount of light they produce, either monthly or yearly. They also rhythmically change how they embrace the horizon, creating a measure of time and seasons. In contrast, the stars are many and their light is small. Their place in the sky is fixed and, ignoring precession, their relationship to the horizon is constant, always rising or setting at the same point. They are different in almost every way to the luminaries, in their multiplicity, light, fixed spatial relationship to each other and fixity in a landscape. These distinct characteristics mean that the stars are a catalyst for sky narratives quite different from those of the luminaries. The most easily recognisable stellar sky narratives are the constellation stories. The multiplicity of the stars produces a scattering of lights across the night sky according to a fixed pattern which, to the human mind - with its apophenia, the tendency to see patterns - results in the heavens becoming a vast storyboard of constellations and clusters. These stories are placed on bright stars, dim stars, coloured stars, dark gaps or voids, and milky hazes. Every spot of the dome of the heavens holds some culture's myth, some culture's cosmic narrative, and every visible place in the dome of the heavens has been claimed by most cultures. Their consistency of movement and fixedness in orientation to each other, however, also offer humanity something quite unique: a view of eternity.

Night vision system has become a critical component of modern warfare and the ability to see in nighttime conditions allows military maneuvers and a potential advantage to the forces equipped with this technology. These night vision systems rely on the very low light levels of night sky illumination to help image the targeted scene and its surroundings. Many research works have been undertaken to overcome issues in hardware implementation. In this paper, we contribute to enhance night vision sources by hybrid vision enhancement (HVE) system without affecting performance of hardware implementation. The proposed hybrid system consists of two algorithms such asoptimizedtone mapping (OTM) and adaptive gamma correction (AGC) algorithm. Normally, hybrid systems are not an area efficient, here we modify the tone mapping algorithm byoptimized filter design with the exponential basis. The differential evolution optimization algorithm is used to enhance the filter design. The proposed HVE system implementation is designed in Verilog language and synthesized with different FPGA device families in Xilinx tool. Simulation result shows that our proposed HVE system is able to enhance vision of wide dynamic range (WDR) images to good visual quality. The synthesis result shows that our proposed HVE system perform very efficient than existing system in terms of hardware utilization, maximum clock frequency, and power.

We present a simplified method using geographic analysis tools to predict the average artificial luminance over the hemisphere of the night sky, expressed as a ratio to the natural condition. The VIIRS Day/Night Band upward radiance data from the Suomi NPP orbiting satellite was used for input to the model. The method is based upon a relation between sky glow brightness and the distance from the observer to the source of upward radiance. This relationship was developed using a Garstang radiative transfer model with Day/Night Band data as input, then refined and calibrated with ground-based all-sky V-band photometric data taken under cloudless and low atmospheric aerosol conditions. An excellent correlation was found between observed sky quality and the predicted values from the remotely sensed data. Thematic maps of large regions of the earth showing predicted artificial V-band sky brightness may be quickly generated with modest computing resources. We have found a fast and accurate method based on previous work to model all-sky quality. We provide limitations to this method. The proposed model meets requirements needed by decision makers and land managers of an easy to interpret and understand metric of sky quality.

The concept of the System for the Observation of Daytime Asteroids (SODA system) has been developed, the purpose of which is to detect at least 95% of hazardous celestial bodies larger than 10 m in size that fly towards Earth from the Sun side. Spacecraft, equipped with the optimum version, which has three wide-angle optical telescopes of small aperture (20–30 cm) will be placed in a halo orbit around the L1 libration point of the Sun–Earth system. This will provide a warning on the hazardous object, approaching from the Sun side, and will allow one to determine the orbit and the point of body entering Earth atmosphere to a sufficient accuracy, at least a few hours before the body collides with Earth. The requirements to the system are considered, the results of a preliminary design of the set of instruments have been described, the areas of visibility are calculated, and the versions of data transmission modes have been proposed. It has been shown that, in cooperation with other (particularly ground-based) projects aimed to observing objects flying from the night sky side, it is possible to detect in advance all hazardous bodies in the near-Earth space larger than 10 m in size that approach Earth from almost any direction.

The knowledge of the emission function of a city is crucial for simulation of sky glow in its vicinity. The indirect methods to achieve this function from radiances measured over a part of the sky have been recently developed. In principle, such methods represent an ill-posed inverse problem. This paper deals with the theoretical feasibility study of various approaches to solving of given inverse problem. Particularly, it means testing of fitness of various stabilizing functionals within the Tikhonov’s regularization. Further, the L-curve and generalized cross validation methods were investigated as indicators of an optimal regularization parameter. At first, we created the theoretical model for calculation of a sky spectral radiance in the form of a functional of an emission spectral radiance. Consequently, all the mentioned approaches were examined in numerical experiments with synthetical data generated for the fictitious city and loaded by random errors. The results demonstrate that the second order Tikhonov’s regularization method together with regularization parameter choice by the L-curve maximum curvature criterion provide solutions which are in good agreement with the supposed model emission functions.

To understand the night sky radiance generated by the light emissions of urbanised areas, different researchers are currently proposing various theoretical approaches. The distribution of the radiant intensity as a function of the zenith angle is one of the most unknown properties on modelling skyglow. This is due to the collective effects of the artificial radiation emitted from the ground-based light sources. The emission function is a key property in characterising the sky brightness under arbitrary conditions, therefore it is required by modellers, environmental engineers, urban planners, light pollution researchers, and experimentalists who study the diffuse light of the night sky. As a matter of course, the emission function considers the public lighting system, which is in fact the main generator of the skyglow. Still, another class of light-emitting devices are gaining importance since their overuse and the urban sprawl of recent years. This paper will address the importance of the emission function in modelling skyglow and the factors involved in its characterization. On this subject, the author's intention is to organise, integrate, and evaluate previously published research in order to state the progress of current research toward clarifying this topic.

A new portable sky scanner designed for low-light-level detection at night is developed and employed in night sky brightness measurements in a rural region. The fast readout, adjustable sensitivity and linear response guaranteed in 5–6 orders of magnitude makes the device well suited for narrow-band photometry in both dark areas and bright urban and suburban environments. Quasi-monochromatic night-sky brightness data are advantageous in the accurate characterization of spectral power distribution of scattered and emitted light and, also allows for the possibility to retrieve light output patterns from whole-city light sources. The sky scanner can operate in both night and day regimes, taking advantage of the complementarity of both radiance data types. Due to its inherent very high sensitivity the photomultiplier tube could be used in night sky radiometry, while the spectrometer-equipped system component capable of detecting elevated intensities is used in daylight monitoring. Daylight is a source of information on atmospheric optical properties that in turn are necessary in processing night sky radiances. We believe that the sky scanner has the potential to revolutionize night-sky monitoring systems.

We present an analysis of the zenithal night sky brightness (henceforth: NSB) measurements at 26 locations in Eastern Austria focussing on the years 2015-2016, both during clear and cloudy to overcast nights. All measurements have been performed with 'Sky Quality Meters' (SQMs). For some of the locations, simultaneous aerosol content measurements are available, such that we were able to find a correlation between light pollution and air pollution at those stations. For all locations, we examined the circalunar periodicity of the NSB, seasonal variations as well as long-term trends in the recorded light pollution. For several remote locations, a darkening of the night sky due to clouds by up to 1 magnitude is recorded - indicating a very low level of light pollution -, while for the majority of the examined locations, a brightening of the night sky by up to a factor of 15 occurs due to clouds. We present suitable ways to plot and analyze huge long-term NSB datasets, such as mean-NSB histograms, circalunar, annual ('hourglass') and cumulative ('jellyfish') plots. We show that five of the examined locations reach sufficiently low levels of light pollution - with NSB values down to 21.8 mag$_{SQM}$/arcsec$^2$ - as to allow the establishment of dark sky reserves. Based on the 'hourglass' plots, we find a strong circalunar periodicity of the NSB in small towns and villages (< 5.000 inhabitants), with amplitudes of of up to 5 magnitudes. Using the 'jellyfish' plots, on the other hand, we demonstrate that the examined city skies brighten by up to 3 magnitudes under cloudy conditions, which strongly dominate in those cumulative data representations. The long-term development of the night sky brightness was evaluated based on the 2012-17 data for one of our sites, possibly indicating a slight (~2%) decrease of the mean zenithal NSB at the Vienna University Observatory., Accepted by JQSRT, 2018

Illumina is one of the most physically detailed artificial night sky brightness model to date. It has been in continuous development since 2005 [1]. In 2016–17, many improvements were made to the Illumina code including an overhead cloud scheme, an improved blocking scheme for subgrid obstacles (trees and buildings), and most importantly, a full hyperspectral modeling approach. Code optimization resulted in significant reduction in execution time enabling users to run the model on standard personal computers for some applications. After describing the new schemes introduced in the model, we give some examples of applications for a peri-urban and a rural site both located inside the International Dark Sky reserve of Mont-Megantic (QC, Canada).

Since prehistory, humans have looked to the stars and seen gods and monsters. But now there are new constellations in the night sky. Their invisible lines criss-cross the cosmos, linking stars of different ages, colours and brightness in a tangled network that seems at first to have no clear purpose. But unlike the familiar classical constellations, these are more than aesthetically pleasing patterns: they mark out the first family tree of the stars. For now this is just a tentative sketch of stellar heredity, but it is already providing intriguing insights. As the tree grows, it could reveal the origin of the sun and tell us how the galaxy grew. But as the two discussed the question, it' became clear that, in a manner of speaking, stars do reproduce.Deep within a star, nuclear fusion reactions forge light elements into heavier ones, which are then returned to space as the star reaches the end of its life.

Within the big city boundaries, artificial component of the sky glow increases every year. The main reasons are the expansion of the cities, the rapid growth of technical capabilities, inefficient lighting design without master-planning and lack of quality control of lighting projects. The data of astronomical observations confirm a significant brightness increasing in the lower atmosphere due to factors of terrestrial origin. The problem is mostly acute for observatories are located near major cities, which are struggling for the possibility of further research. Night sky background glow estimation is an actual direction for research in the modern world. The paper considers a model for calculating the sky brightness for the St. Petersburg city. According to the developed model observation position is located near the Pulkovo Observatory. The model is based on the Garstang’s method with use of Python programming language.

The mechanism in which multiple scattering influences the radiance of a night sky has been poorly quantified until recently, or even completely unknown from the theoretical point of view. In this paper, the relative contribution of higher-scattering radiances to the total sky radiance is treated analytically for all orders of scattering, showing that a fast and accurate numerical solution to the problem exists. Unlike a class of ray tracing codes in which CPU requirements increase tremendously with each new scattering mode, the solution developed here requires the same processor time for each scattering mode. This allows for rapid estimation of higher-scattering radiances and residual error that is otherwise unknown if these radiances remain undetermined. Such convergence testing is necessary to guarantee accuracy and the stability of the numerical predictions. The performance of the method developed here is demonstrated in a set of numerical experiments aiming to uncover the relative importance of higher-scattering radiances at different distances from a light source. We have shown, that multiple scattering effects are generally low if distance to the light source is below 30 km. At large distances the multiple scattering can become important at the dark sky elements situated opposite to the light source. However, the brightness at this part of sky is several orders of magnitude smaller than that of a glowing dome of light over a city, so we do not expect that a partial increase or even doubling the radiance of otherwise dark sky elements can noticeably affect astronomical observations or living organisms (including humans). Single scattering is an appropriate approximation to the sky radiance of a night sky in the vast majority of cases.

Given the global continuous rise, artificial light at night is often considered a driving force behind moth population declines. Although negative effects on individuals have been shown, there is no evidence for effects on population sizes to date. Therefore, we compared population trends of Dutch macromoth fauna over the period 1985–2015 between moth species that differ in phototaxis and adult circadian rhythm. We found that moth species that show positive phototaxis or are nocturnally active have stronger negative population trends than species that are not attracted to light or are diurnal species. Our results indicate that artificial light at night is an important factor in explaining declines in moth populations in regions with high artificial night sky brightness. Our study supports efforts to reduce the impacts of artificial light at night by promoting lamps that do not attract insects and reduce overall levels of illumination in rural areas to reverse declines of moth populations.

Mar Mezcua spends her days hunting invisible game. Lumbering giants, impossible to see with the naked eye, expertly camouflaged in the darkness of the night sky. She knows they're out there; she has seen their footprints, tracked their spoor. But for all the hours she has spent lying in wait for black holes, there is one breed she has never spotted. On paper, they are fairly unremarkable: average size, average mass. Black holes are not easy to study. They are so massive and compact that their gravity sucks in anything venturing too close. Even light cannot escape their gravitational clutches, so they reflect nothing, rendering them all but invisible. For the most part, the black holes found so far can be split into two camps. At the puny end are stellar mass black holes, formed by the explosive deaths of massive stars and typically weighing less than 100 times the mass of our sun

The night sky brightness at the RGN site (near the centre of Zagreb, Croatia) was monitored form January 2012. to December 2017. The gathered data show that the average night sky brightness in this period did not change significantly, apart from differences caused by yearly variations in meteorological parameters. The nightly minima, maxima and mean values of the sky brightness do change considerably due to changes in meteorological conditions, often being between 2 and 3 magnitudes. The seasonal probability curves and histograms are constructed and are used to obtain additional information on the light pollution at the RGN site. They reveal that the night sky brightness clutters around two peaks, at about 15.0 mag/arcsec2 and at about 18.2 mag/arcsec2. The tendency to slightly lower brightness values in spring and summer can also be seen in the data. Two peaks correspond to cloudy and clear nights respectively, the difference in brightness between them being about 3 magnitudes. A crude clear/cloudy criterion can be defined too: the minimum between two peaks is around 16.7 mag/arcsec2. The brightness values smaller than this are attributed to clear nights and vice-versa. Comparison with Vienna and Hong-Kong indicates that the light pollution of Zagreb is a few times larger., Comment: Submitted to The Mining Geological Petroleum Engineering Bulletin (https://www.scopus.com/sourceid/101730) February 27, 2018

Measuring the brightness of the night sky has become an increasingly important topic in recent years, as artificial lights and their scattering by the Earths atmosphere continue spreading around the globe. Several instruments and techniques have been developed for this task. We give an overview of these, and discuss their strengths and limitations. The different quantities that can and should be derived when measuring the night sky brightness are discussed, as well as the procedures that have been and still need to be defined in this context. We conclude that in many situations, calibrated consumer digital cameras with fisheye lenses provide the best relation between ease-of-use and wealth of obtainable information on the night sky. While they do not obtain full spectral information, they are able to sample the complete sky in a period of minutes, with colour information in three bands. This is important, as given the current global changes in lamp spectra, changes in sky radiance observed only with single band devices may lead to incorrect conclusions regarding long term changes in sky brightness. The acquisition of all-sky information is desirable, as zenith-only information does not provide an adequate characterization of a site. Nevertheless, zenith-only single-band one-channel devices such as the Sky Quality Meter continue to be a viable option for long-term studies of night sky brightness and for studies conducted from a moving platform. Accurate interpretation of such data requires some understanding of the colour composition of the sky light. We recommend supplementing long-term time series derived with such devices with periodic all-sky sampling by a calibrated camera system and calibrated luxmeters or luminance meters., 44 pages, 11 figures

Measuring the brightness of the night sky and determining the start of Fajr prayer times can be done using SQM. Observations were made at OIF UMSU with coordinates 3o 34' 55.06" N and 98o 43' 17.09" E. The sky brightness was measured using three SQMs mounted facing the zenith, eastern horizon, and western horizon. The night sky brightness values for SQM directed to the zenith, eastern horizon, and western horizon are 18.23 mpsas, 15.82 mpsas, and 15.47 mpsas. The beginning of fajr prayer time produced by SQM is after the beginning of fajr prayer time obtained using the Accurate Times concerning the Sun's altitude 18o below the horizon. The difference obtained by SQM directed to the zenith, eastern horizon, and western horizon is 29.5 minutes, 36.7 minutes, and 39.5 minutes. In other words, the beginning of Fajr prayer time used in Indonesia is earlier than it should be.

The winter solstice marks the astronomical moment when the sun is aligned over the Tropic of Capricorn. On December 21, those who live in the Northern Hemisphere had the shortest day and longest night of the year. This was accompanied in 2020 by a rare alignment of Jupiter and Saturn, which appeared as a singular bright point of light in the night sky for the first time since the Middle Ages. Although many cultures celebrate the winter solstice, the solstice is mostly overlooked in the United States, largely because of the multitude of other holidays around this time of the year. However, the shortest day and longest night seems like a metaphor of sorts for a year like no other in the memory of most-a fitting end and a pause. From the stillness, we can reflect in the space between the past and the future, reviewing the year behind us while appreciating the challenges to be faced in 2021.

Our love of looking up The night sky has wowed people since the dawn of time, but it is becoming increasingly difficult to get a good view, writes Chanda Prescod-Weinstein

All meteor showers dazzle the night sky, but the Perseids shower is special. Here's how to enjoy it this month, says Abigail Beall

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 kilometer 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 anaysis of several regions of the world, based on the data from the New world atlas of artificial night sky brightness (Falchi et al 2016, Sci. Adv. 2, e1600377) suggests that, as a rule of thumb, about one measurement per square kilometer could be sufficient for determining the zenithal night sky brightness of artificial origin at any point in a region to within 0.1 magV/arcsec2 (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., Accepted version, Monthly Notices of the Royal Astronomical Society

Light pollution is a topic gaining importance and acceptance in environmental discourse. This concept provides a framework for categorizing the adverse effects of nighttime lighting, which advocacy groups and regulatory efforts are increasingly utilizing. However, the ethical significance of the concept has, thus far, received little critical reflection. In this paper, I analyze the moral implications of framing issues in nighttime lighting via the concept of light pollution. First, the moral and political importance of problem framing is discussed. Next, the origins and contemporary understandings of light pollution are presented. Finally, the normative limitations and practical ambiguities of light pollution are discussed, with the aim of strengthening the framework through which decisions about urban nighttime lighting strategies are increasingly approached.

We develop a model and prototype for a lightweight roof oculus structure, which integrates two complementing cooling strategies. During the day the roof oculus takes the shape of a downdraft evaporative cooling chimney. A water mist sprays inside the chimney crown, cooling and densifying hot dry air and causing it to fall down the chimney into the indoor space by free convection. During the night, the oculus structure is opened by geometric dilation designed with actuation kinetics to expose a maximum surface of the concrete slab below to the night sky above. The slab then acts as thermal mass, “storing” coolness for the following hot day. The results of the analytical model demonstrate the ability to cool a space in 40°C desert climate to comfort conditions. A scaled prototype was built and demonstrates the operation to evaporative cooling and the structural opening for expanded radiant view factor.

We present the main features of TESS-W, the first version of a series of inexpensive but reliable photometers that will be used to measure night sky brightness. The bandpass is extended to the red with respect of that of the Sky Quality Meter (SQM). TESS-W connects to a router via WIFI and it sends automatically the brightness values to a data repository using Internet of Things protocols. The device includes an infrared sensor to estimate the cloud coverage. It is designed for fixed stations to monitor the evolution of the sky brightness. The photometer could also be used in local mode connected to a computer or tablet to gather data from a moving vehicle. The photometer is being developed within STARS4ALL project, a collective awareness platform for promoting dark skies in Europe, funded by the EU. We intend to extend the existing professional networks to a citizen-based network of photometers.

This paper discusses the feasibility of cooling using radiation under Hong Kong’s hot and humid climate. Three different designs of a passive radiative cooler were studied in this work. The three designs include non-vacuum, and vacuum with seven potassium chloride (KCl) IR-Pass windows as well as one system with a single KCl IR-Pass window. The coolers were examined during daytime and night time operation as well as under different sky conditions, such as clear, cloudy and partly cloudy. Investigation was mainly based on the temperature difference between the radiative cooler and ambient air. The experimental results showed that the passive radiative cooler with seven KCl windows and the cooler design without vacuum provided a satisfactory cooling effect at night (i.e. the ambient air temperature was reduced by about 6–7 °C), but the coolers could not produce a cooling effect during daytime under any of Hong Kong’s weather conditions. The same results were obtained for the passive radiative cooler with the single KCl window during daytime operation. However, the cooling capacity of the passive radiative cooler design without vacuum under a clear night sky achieved 38 W/m2.

Night sky radiant cooling is one of such promising natural techniques that can be worth a high recommendation. In this study, a novel design of night sky radiation heat exchanger is proposed, and i...

Light pollution is closely correlated with the meteorological factors, specifically cloudiness that is one of the major amplifiers of night sky radiances in urban regions. Although the decisive effects of cloud deck on artificial nighttime skyglow have been recognized experimentally, the radiative transfer modelling in a heterogeneous nocturnal environment illuminated from many light sources is a non-trivial problem that is difficult to solve both theoretically and numerically. A satisfactorily accurate evaluation of ground-reaching diffuse light is, however, an important issue as some optical properties (e.g. horizontal irradiance) are usually difficult to obtain with common instruments. Overcast sky represents a special class of situations in which clouds can act as amplifiers of the light pollution of the city. In this paper we proceeded with a simple two-stream approach to solve the scalar radiative transfer equation (RTE) under overcast conditions. The technique we are using allows for a rapid prediction of ground irradiances in densely populated regions assuming various emission functions. We have shown that the classical RTE concept can be adopted in determining the diffuse irradiance, while the model abilities are illustrated in a set of numerical experiments for low and high turbidity states.

The 197 radio astronomy dishes of the Square Kilometre Array (SKA) in South Africa, due for completion later this decade, may find itself threatened from above by tens of thousands of communications satellites beaming down radio signals. The rocket company SpaceX has already launched hundreds of Starlink satellites, the first "megaconstellation" intended to provide internet service to remote areas. The satellites have aroused the ire of optical astronomers because of the bright streaks they leave across telescopes9 fields of view. Now, radio astronomers are worried, too. Last week, SKA released an analysis of the impact that Starlink and other constellations would have on the array. The United Nations Office for Outer Space Affairs is also considering ways to keep satellites from polluting the night sky with light and radio signals and astronomers hope the International Telecommunication Union, a U.N. organization, will step in.

What does gazing up at the night sky have in common with the COVID‐19 pandemic? Even though no matter can travel faster than light, the speed of the latter is constant and finite, and hence when we look at the night sky, we see stars and galaxies in the way they were in the past, for the starlight that we see at any given point in time travelled for years before it reached us This phenomenon offers an apt analogy to the challenges that we are faced with today, when, amidst the COVID‐19 pandemic, we attempt to understand the gravity of the situation and to plan our responses to it by relying on the available numbers of confirmed cases and deaths linked to the virus Putting aside the fact that only a fraction of all cases is officially registered, this data, just like stars, is not indicative of the situation in the present, but rather offers a glimpse into the past

Light emitted or reflected up to the sky can interact with clouds or fog changing Night Sky Brightness (NSB). So the evaluation of NSB in any place can be affected by this meteorological features and needs to be analyzed. To evaluate this effect, data of NSB obtained with the Catalan Light Pollution Network (XCLCat) has been analyzed accurately and shows how the effect is completely different in urban and protected areas. The study, including for the first time independent cloud coverage data from ceilometer in combination with Sky Quality Meters (SQM), shows how in a city NSB increases dramatically and in a protected area the sky appears darker than in cloudless situation.

Traditional medicine scientists believed that sleeping under the stars and moonlight is not healthy because it brings about nose bleeds and respiratory problems. In Avicenna's view, the spirit and its tendency to the light are introduced as main etiology, which cannot explain star light as a proper etiology. In modern knowledge, it seems cosmic rays that reach our planet's atmosphere by electron cascade, play a key role. Internal organs' electrical charge distribution disturbance caused by these electrons can lead to irregular spasms in the muscular walls of arteries and other organs. These interactions may finally lead to circulation (epistaxis and hypertension) and respiratory (catarrh) problems.

Light pollution poses a growing threat to optical astronomy, in addition to its detrimental impacts on the natural environment, the intangible heritage of humankind related to the contemplation of the starry sky and, potentially, on human health. The computation of maps showing the spatial distribution of several light pollution related functions (e.g. the anthropogenic zenithal night sky brightness, or the average brightness of the celestial hemisphere) is a key tool for light pollution monitoring and control, providing the scientific rationale for the adoption of informed decisions on public lighting and astronomical site preservation. The calculation of such maps from satellite radiance data for wide regions of the planet with sub-kilometric spatial resolution often implies a huge amount of basic pixel operations, requiring in many cases extremely large computation times. In this paper we show that, using adequate geographical projections, a wide set of light pollution map calculations can be reframed in terms of two-dimensional convolutions that can be easily evaluated using conventional fast Fourier-transform (FFT) algorithms, with typical computation times smaller than 10^-6 s per output pixel., Author formatted text of the accepted version of the paper published in Journal of Quantitative Spectroscopy & Radiative Transfer 240 (2020) 106658