Artificial Sky Research Articles

Correction: Artificial skies: why insects get stuck circling lights at night.

Correction: Artificial skies: why insects get stuck circling lights at night.

Artificial skies: why insects get stuck circling lights at night

Artificial skies: why insects get stuck circling lights at night

“He would Thunder from an Artificial Sky, as Salmoneus”: Constantine Komnenodoukas’ Patronage of a ‘Persian’ soufa in Naupaktos (ca. 1220)

Abstract Around 1220, Constantine Komnenodoukas undertook the construction of an unconventional building in Naupaktos, Greece, referred to as a ‘Persian’ soufa. Information on this construction is contained in a letter written by the city’s metropolitan, John Apokaukos, who maintained an adversarial rapport with him. The soufa is described as a rectangular structure with two levels. In the higher one, reserved for Constantine and his retinue, a throne shaped as an episcopal throne was placed. Conversely, the lower level accommodated more humble guests who could only listen to him thundering like Salmoneus from an artificial sky. This architectural venture served as a symbolic manifestation of Constantine’s secular authority, deliberately positioned in contrast to the ecclesiastical figure of the bishop. Noteworthy is Constantine’s deliberate appropriation of ideas, forms, and language acquired during his sojourn in Asia Minor several years before. The resulting structure stands as a singular manifestation, representing a distinctive historical juncture influenced by the personality of Constantine Komnenodoukas, wherein elements of both Byzantine and Islamic art are combined.

Evaluating the benefits of dark and quiet skies in an age of satellite mega-constellations

In an age of proliferating satellite constellations and congested Earth orbits, what is the status and value of dark and quiet skies? Satellite mega-constellations such as Starlink are illuminating the night sky with unnatural light and making astronomical observations—both professional and recreational—increasingly difficult. Radio frequency interference (RFI) from these constellations also adds obtrusive “noise,” impacting sensitive astronomical observations in the radio portion of the electromagnetic spectrum. Scientists predict that the growing commercial space sector will add more than 100,000 satellites to Earth's orbit by the end of the decade, raising concerns from numerous scientists as to the future of dark skies. Astronomy, in particular, is inevitably affected by the impending disappearance of dark and quiet skies, which are necessary conditions for many aspects of scientific research. This topic has also gained attention, at both the international level and national level, within the United States. Nonetheless, contributions to the conversation of mitigating light/noise pollution predominantly focus on the likely adverse effects of artificial sky brightening from satellites. A holistic discussion is also warranted on the benefits of existing night skies and their significance for society.This paper addresses the positive value of dark skies and the significance of protecting astronomy through current governing and analogous frameworks. First, this paper evaluates dark skies’ application under existing international and national law and policy, highlighting lacunae in governance and outlining convoluted issues for Earth-based science (astronomy) versus the lawful use of space (satellites). U.S. space law is used as a case study given the extensive history of the United States in space, comprehensive U.S. space political infrastructures, and the burgeoning domestic satellite mega-constellation industry. Second, relevant ethical values are identified to clarify inherent moral considerations that can guide policymaking and serve to establish practical measures and approaches to balance the conflicting interests of astronomers and satellite operators. Significantly, this paper contributes to the topic by explaining how the advent of technological change creates new conflicts on Earth and expounds on how and why these issues are lacking or are inadequate under current international frameworks. Moreover, this work explores key ethical values on this topic for informing public policy on dark and quiet skies and highlights some mechanisms for resolving these conflicts. In conclusion, the recession of dark skies is already occurring, and the likely impacts require transparency, good will, and interdisciplinary compromise between scientists, policymakers, and the space industry.

Nearby night lighting, rather than sky glow, is associated with habitat selection by a top predator in human-dominated landscapes.

Artificial light at night (ALAN) is increasing in extent and intensity across the globe. It has been shown to interfere with animal sensory systems, orientation and distribution, with the potential to cause significant ecological impacts. We analysed the locations of 102 mountain lions (Puma concolor) in a light-polluted region in California. We modelled their distribution relative to environmental and human-disturbance variables, including upward radiance (nearby lights), zenith brightness (sky glow) and natural illumination from moonlight. We found that mountain lion probability of presence was highly related to upward radiance, that is, related to lights within approximately 500 m. Despite a general pattern of avoidance of locations with high upward radiance, there were large differences in degree of avoidance among individuals. The amount of light from artificial sky glow was not influential when included together with upward radiance in the models, and illumination from moonlight was not influential at all. Our results suggest that changes in visibility associated with lunar cycles and sky glow are less important for mountain lions in their selection of light landscapes than avoiding potential interactions with humans represented by the presence of nearby lights on the ground. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Global erosion of terrestrial environmental space by artificial light at night

Artificial light at night (ALAN) disrupts natural light cycles, with biological impacts that span from behaviour of individual organisms to ecosystem functions, and across bacteria, fungi, plants and animals. Global consequences have almost invariably been inferred from the geographic distribution of ALAN. How ALAN is distributed in environmental space, and the extent to which combinations of environmental conditions with natural light cycles have been lost, is also key. Globally (between 60°N and 56°S), we ordinated four bioclimatic variables at 1.61 * 1.21 km resolution to map the position and density of terrestrial pixels within nighttime environmental space. We then used the Black Marble Nighttime Lights product to determine where direct ALAN emissions were present in environmental space in 2012 and how these had expanded in environmental space by 2022. Finally, we used the World Atlas of Artificial Sky Brightness to determine the proportion of environmental space that is unaffected by ALAN across its spatial distribution. We found that by 2012 direct ALAN emissions occurred across 71.9 % of possible nighttime terrestrial environmental conditions, with temperate nighttime environments and highly modified habitats disproportionately impacted. From 2012 to 2022 direct ALAN emissions primarily grew within 34.4 % of environmental space where it was already present, with this growth concentrated in tropical environments. Additionally considering skyglow, just 13.2 % of environmental space now only experiences natural light cycles throughout its distribution. With opportunities to maintain much of environmental space under such cycles fast disappearing, the removal, reduction and amelioration of ALAN from areas of environmental space in which it is already widespread is critical.

The use of polarized light in the zonal orientation of the sandhopper Talitrus saltator (Montagu)

It is well known that the celestial polarization is used as a compass cue by many species of insects and crustaceans. Although it has been shown that the sandhopper Talitrus saltator perceives polarized light and possesses an arrangement of the rhabdomeres that could allow e-vector interpretation and utilization, T. saltator does not use the e-vector of the skylight polarization as a compass cue when making excursions along the sea–land axis of sandy shores. We performed tests in confined conditions to clarify if skylight polarization is somehow involved in the zonal recovery of T. saltator. We observed the directional responses of sandhoppers in a transparent bowl under an artificial sky (an opaline Plexiglas dome). The bowl was covered by a blue gelatin filter with a grey filter (control condition) and a linear polarizing filter (experimental conditions) positioned under the blue one in such a way as to occupy half of the upper surface of the Plexiglas bowl so as to create a linear polarization gradient. Our experiments confirm that T. saltator perceives polarized light and highlight that this visual capability determines the perception, or perhaps the increase, of the radiance and/or spectral gradient and their use as compass cues in the zonal orientation. Moreover, our findings confirm that the radiance gradient is used as a chronometric compass orienting reference in the absence of other celestial orienting cues.

Lighting of pedestrian and pedestrian-driving routes in a housing estate as a source of light pollution

This paper is devoted to the extremely important issue of lighting pedestrian and pedestrian-driving routes within a housing estate. Both aspects are discussed with regard to the safety of route users and the potential impact on the natural environment through the phenomenon of light pollution. It was found that most of the outdated high-pressure sodium lamps present in the analysed Podwawelskie housing estate in Kraków do not fulfil their basic purpose, which is to sufficiently illuminate the ground below. Nevertheless, the light of these lamps does not make a noticeable contribution to the basic form of light pollution, which is the city's sky glow. It has been suggested that it would be best to replace these types of lamps with LED lighting, which has already been partly done. The LED lamps provide lighting that is sufficient to ensure the safety of residents. However, their improper installation may cause glare for pedestrians or residents of neighbouring houses. Additionally, their light reflected from an excessively bright pavement makes a significant contribution to the artificial sky glow. Solutions are proposed that minimise the negative impact of this lighting on the environment while ensuring comfort for the residents of the estate, which is in line with the principles of sustainable development.

Majority of artificially lit Earth surface associated with the non-urban population

Key to understanding the negative impacts of artificial light at night (ALAN) on human health and the natural environment is its relationship with human density. ALAN has often primarily been considered an urban issue, however although over half of the population is urbanized, the 46 % that are not inhabit a dispersed array of smaller settlements. Here, we determine the global relationships between two dimensions of ALAN, namely direct emissions (radiance) and skyglow, and human density, and how these relationships vary across continents. We correct the Visible Infrared Imaging Radiometer Suite Day/Night Band (VIIRS DNB) product for albedo, skyglow, airglow, the aurora and permanent snow and ice to represent upward radiance overland at 1.61 ∗ 2.12 km resolution from artificial sources only. For skyglow we use the World Atlas of Artificial Sky Brightness. Globally (between 59°N and 55°S), direct emissions were detected over 26.5 % and skyglow over 46.9 % of land area. Over half of all cumulative direct emissions (54.9 %) were emitted at low levels by the non-urban population, whilst these populations experienced the negative impacts of over two-thirds of all cumulative skyglow (69.8 %). This emphasises the extent of ALAN outside of urban areas, and its similarity in this regard to a number of other forms of pollution. Although powerful sources of rural direct emissions (e.g., industry, recreation) are important contributors of light pollution, cumulatively they only contributed 10 % to total direct emissions. The relationship between each dimension of ALAN and population density varied across continents, driven by powerful rural emissions, non-urban populations and urban design. These relationships reflect the unique socio-economic and geographical make-up of each region and inform on where best to target light pollution mitigation strategies, not only in urban areas but also in rural ones.

Peculiarities of the environmental light pollution in Chernivtsi Region

Introduction. Every year industrial development and economic growth make light pollution worsen on a global scale. It is a well-known fact that artificial outdoor lighting causes destruction of wildlife habitat, impacts circadian rhythms of all living beings, disrupts animal behavior and leads to medical disorders of humans. Over the last decade scientists switched their focus from artificial sky glow over large cities to light pollution of rural landscapes, protected areas and roadways. 
 The purpose of this paper consists in assessing night-time light emissions over Chernivtsi Region as well as over city of Chernivtsi using satellite measurements.
 Methods. Measurements of night-time light emissions were obtained with the help of GIS web application Radiance Light Trends and the light trends analysis tool. The application allows examination of changes in light pollution across selected areas since 1992 and performs time-series analysis with fitting an exponential curve into the data set.
 Results. The trend in light emissions observed by satellites for Chernivtsi Region indicated brightening at the rate of 2.45 % per year from 1992 to 2014, and 2.93 % per year from 2014 to 2021. The marked increase in the intensity of atmospheric light pollution over Chernivtsi Region is largely attributable to urban expansion of district centers, national & international routes and resort complexes. At the same time, the spatial pattern of the light environment over city of Chernivtsi indicated a nearly constant level of aggregate annual light radiance for the last 8 years. A large irregularly shaped "light spot" was detected on the territory of the Prut-Siret interfluve. It crosses the region from the northwest to the southeast and covers the regional center with its suburbs and the national highway H-10. The night light radiance constitutes 47.49∙10-9 mW/cm2 sr in the center of the spot and more than 1∙10-9 mW/cm2 sr at its edges. The highest level of light pollution in Chernivtsi Region was registered in January, and the lowest – in March. Night-time light emission over two most illuminated highways remains relatively constant regardless of the season.
 Conclusion. The study highlights that despite low population and low economic activity, rural landscapes demonstrate a trend towards increasing brightness of the night sky. The findings provide a quantitative reference for light pollution management in the region and for further research in the area.

Point spread functions for mapping artificial night sky luminance over large territories

ABSTRACT Knowledge of the night sky radiance over a large region may be valuable information for identifying sites suitable for astronomical observations or for assessing the impact of artificial light at night on ecosystems. Measuring the sky radiance can be a complex endeavour, depending on the desired temporal and spatial resolution. Likewise, the modelling of artificial night sky radiance for multiple points of a region can represent a significant amount of computing time depending on the complexity of the model used. The use of the convolution of a point spread function with the geographical distribution of light sources has been suggested in order to model the sky radiance over large territories of hundreds of kilometres in size. We determined how the point spread function is sensitive to the main driving parameters of the artificial night sky radiance, such as the wavelength, the ground reflectance, the obstacle properties, the upward light output ratio, and the aerosol optical depth using the Illumina v2 model. The obtained functions were then used to model the artificial night sky brightness of the Mont-Mégantic International Dark Sky Reserve for winter and summer conditions. The results were compared with the New World Atlas of artificial night sky brightness, the Illumina v2 model, and in situ Sky Quality Camera measurements. We found that the New World Atlas overestimates the artificial sky brightness by 55 per cent, whereas the Illumina model underestimates it by 48 per cent. This may be due to varying atmospheric conditions and the fact that the model accounts only for public light sources.

The New Method To Calibrate Iso/cie General Skies modelled In Artificial Skies

Recently sky luminance distributions under fifteen ISO/CIE sky types were standardised in relative terms, i.e. all elementary sky luminance are normalised by the zenith luminance in nature. However, these standard sky luminance patterns can be characterised also in their physical units, see in CIE215:20014 which can be reduced by suitable intensity scales to simulate the very high natural sky luminance in laboratory under artificial sky domes. For the design of the electric illumination system of the artificial sky the appropriate zenith luminance for each sky type has to be derived respecting the indicatrix and gradation functions of each sky type. Thus, the sky patterns simulated in the artificial sky can be calibrated either by luminance measurements or by analysing fish-eye photos taken from the sky centre showing the smoothness and gradual changes of homogeneous sky type luminance patterns. The sky luminance images can be utilised to proceed with the adjustment or dimming of the LED electrical system to the final calibration check containing zenith luminance and exterior illuminance in the second calibration step.

Comparative Study on Computer Simulation of Solar Shading Performance with Heliodon and Artificial Sky

Current technological advancement and the requirement for sustainability-driven practices has birthed increased demands for accuracy in performance and assessment of energy consumption in the built environment. Energy-efficient and sustainable building projects are to large extents dependent on achieving functional solar shading and sufficient daylighting in building interiors. Hence, the understanding and adequate evaluation of the sun and its dynamic influence on buildings right at the early stage of planning and design is essential for the development of performance-driven building designs. In this study, the performance simulation results of Integrated Environmental Solutions <Virtual Environment> software program modules are examined for accuracy in executing performance analysis of solar shading. This study assesses the shading prediction of Suncast; a virtual solar shading calculation tool, and RadianceIES for measuring daylight availability in a tropical climate region. The evaluation of shading performance with Suncast was validated through physical experiment by comparing the results obtained therein with shading analysis outcomes generated on a scale model with the aid of a heliodon. Likewise, RadianceIES daylighting simulations were compared with measurements realised from an artificial sky simulator. The results were further subjected to correlation tests to determine the relationship between simulation and physical experiment results. The computational evaluation approach presented more efficient means of conducting the performance simulations over the physical experiment methods which were limited by mechanical design of the components. Suncast and RadianceIES simulation results presented comparable equivalence with measurement output acquired from the heliodon and artificial sky respectively, with minimal variations in accuracy. Thus, demonstrating the ability of the computational simulation program in accurately predicting solar shading and daylight performance in buildings, this could benefit architects in the proper and efficient design of shading devices for building facades at early design stages.

How are the Mediterranean islands polluted by artificial light at night?

The Mediterranean is considered as a World Biodiversity Hotspot because of the significant reservoir of endemics, which are threatened with destruction. Island ecosystems have special importance for biodiversity conservation in this region. However, most of them are under strong anthropogenic influences: recreational pressures, infrastructure development, fires etc. At the same time, new types of anthropogenic pressures have developed, one of which is the preponderance of artificial light at night (ALAN) and sky glow. This factor has not been perceived as dangerous for people and biodiversity until recently. However, the latest researches show the opposite conclusion: ALAN has a significant influence on reproduction, navigation, behavior, foraging, habitat selection, communication, and social interactions of all living organisms. Therefore, we have estimated the level of light pollution on the fifteen biggest islands of the Mediterranean using tools available from Google Earth Pro, and the New World Atlas of Artificial Sky Brightness in the form of a kmz layer created by Falchi et al. (2016). In addition, islands or their parts without ecological light pollution have been selected. The obtained results argue that light pollution is extremely high on these larger islands; there are no areas with zero-level of ecological light pollution. As well it has been found that the level of light pollution of these islands correlates with their human population density. Nevertheless, there are 49 small islands or their parts with “pristine” skies, and their total area is 118.67 km2. Also, four dark sky refugia (Western (313,593 km2), Adriatic (331 km2), Aegean (12,448 km2), and Eastern (841,195 km2)) were highlighted within the territory of the Mediterranean Sea. That is 46,61% of its total area. Special attention has been paid to protected areas of the region in the context of combating light pollution, as well as the potential for astro-tourism development. Recommendations for changing of the current ALAN-related situation are given.

On Methodology for Designing Architectural Lighting of Production Site Interior Part 111: Results and Conclusions

This is the final, third part, on the presentation of Chapter 4 and the results of the Vladimir Voronov thesis [1], successfully defended at the Moscow Architectural Institute in 1985 and devoted to the author’s method of designing architectural lighting for industrial interiors with three main upper lantern types of natural daylight and artificial lighting. The method was developed on the basis of longterm analytical calculations and numerous experiments conducted according to all the laws of statistics in natural conditions and in the camera “Mirror-type artificial sky” created by the author using planar and volumetric (on mock-ups) light modelling with careful measurement of lighting parameters characterizing various states, qualities and options for luminance composition, light saturation of the interior space, contrast of lighting, etc. The conclusions of the dissertation give a general picture of the research work performed, the main meaning of which is the belief that the design of lighting in industrial (and in any other) interiors is not limited to providing elementary normalized lighting parameters, but is a complex, sophisticated, and creative task of architectural design where the light – natural and artificial – is the main “actor”, providing functional and aesthetic qualities to the interior.

Restoring the night sky darkness at Observatorio del Teide: First application of the model Illumina version 2

ABSTRACT The propagation of artificial light into real environments is complex. To perform its numerical modelling with accuracy, one must consider hyperspectral properties of the lighting devices and their geographic positions, the hyperspectral properties of the ground reflectance, the size and distribution of small-scale obstacles, the blocking effect of topography, the lamps angular photometry and the atmospheric transfer function (aerosols and molecules). A detailed radiative transfer model can be used to evaluate how a particular change in the lighting infrastructure may affect the sky radiance. In this paper, we use the new version (v2) of the Illumina model to evaluate a night sky restoration plan for the Teide Observatory located on the island of Tenerife, Spain. In the past decades, the sky darkness was severely degraded by growing light pollution on the Tenerife Island. In this work, we use the contribution maps giving the effect of each pixel of the territory to the artificial sky radiance. We exploit the hyperspectral capabilities of Illumina v2 and show how the contribution maps can be integrated over regions or municipalities according to the Johnson–Cousins photometric bands spectral sensitivities. The sky brightness reductions per municipality after a complete shutdown and a conversion to light-emitting diodes are calculated in the Johnson–Cousins B, V, R bands. We found that the conversion of the lighting infrastructure of Tenerife with LED (1800 and 2700 K), according to the conversion strategy in force, would result in a zenith V-band sky brightness reduction of ≈0.3 mag arcsec−2.

Night sky brightness simulation over Montsec protected area

Night sky brightness over Montsec Observatory (north-east of Spain) has been computed and checked against measurements using Illumina numerical model [2]. In a previous publication [20] the methodology was validated and light pollution received in the observatory coming from a unique city was computed. Here we present a simulation that includes all the sources that has a significant impact over the quality of the night sky in this area. The decision of which sources should be included in the simulations was taken following the methodology explained by [6]: using a point spread function (PSF) as a simple approach to estimate which sources are brightening the sky dome over the observer. An ad hoc PSF derived with Illumina was used with the purpose of avoiding to have to rely on already existing empirical PSF. The resulting PSF can be used in any location with similar atmospheric conditions. Differences in the spectrum of the lamps can be accounted easily by adjusting a spectrum scale factor. Illumina simulates the artificial sky brightness received (W/sr/m2) by an observer from any direction. Adding the natural sky brightness allows to compare the simulations to measurements taken with different instrumentation. In our case simulations were checked against ASTMON, SQC and SQM measurements. They show a good agreement both in absolute values and in geographical patterns for the three filters studied, B, V and R. The methodology presented opens many possibilities, such as increasing the reliability of the maps that point out the light pollution main contributors for any location, and reducing the amount of time needed to perform an accurate simulation of the night sky brightness.

Is Artificial Light at Night Dangerous for the Balkan Strict Protected Areas at Present?

The Balkan Peninsula has rich biodiversity with a large number of endemic species; therefore, a part of its territory has been recognized as a World Biodiversity Hotspot. Despite nature conservation efforts and development of nature conservation networks in countries of the region, anthropogenic influence on natural and semi natural ecosystems is increasing. Moreover, new types of disturbance and pollution arise, and one of the more recent being artificial light at night (ALAN) which has serious consequences on reproduction, navigation, foraging, habitat selection, communication, trophic and social interactions of the biota. We have estimated the level of ecological light pollution in the strict protected areas of the Republic of Serbia, the Republic of Bulgaria, and Montenegro using available Google Earth Pro tools, and the New World Atlas of Artificial Sky Brightness (2016) in the form of a kmz layer. The research has covered 13 National Parks, 11 Nature Parks and 55 Reserves. Our results showed widespread incursion of ALAN within strict protected areas in the studied region that has also been noted for some other countries and regions too. However, the level of light pollution is lower here, than in the most part of Continental Europe, and there are a few areas in each country where the night sky above National and Natural Parks is almost dark. These territories have a special value for nature conservation; therefore, it is important to save the dark night sky there.

Efficient circadian daylighting: A proposed equation, experimental validation, and the consequent importance of room surface reflectance

With the increasing understanding of light's non-visual impact on human circadian system, applying circadian daylighting in buildings becomes attractive. The successful adoption of circadian daylighting requires a considerable amount of light incident at the eyes without causing discomfort glare. Therefore, developing daylighting strategies that can efficiently provide indirect corneal illuminance is a promising approach.An equation is proposed to establish the dependence of daylight-enabled corneal illuminance, especially its indirect component, on room surface reflectance and window-to-wall ratio (WWR). The accuracy of the equation is validated in an artificial sky lab which mimics a fixed overcast sky condition. Experiments using scaled room models with various combinations of interior surface reflectance, WWRs, testing locations and measurement directions prove that the proposed equation is accurate. The results suggest that room surface reflectance plays a dominant role in maximizing indirect corneal illuminance. This is further confirmed by performing a Radiance lighting simulation analysis on daylight-enabled morning-hour Circadian Stimulus in a classroom, which supports the proposed equation as well. This work concludes that the proposed equation can provide quick estimation in circadian daylighting design and that high room surface reflectance is the key to achieve efficient and quality circadian daylighting.

Sky radiance and spectral gradient are orienting cues for the sandhopper Talitrus saltator (Crustacea, Amphipoda).

The sandhopper Talitrus saltator relies on both the sun and the moon compasses to return to the belt of damp sand on the beach in which it lives buried during the day. In addition to the sun, the gradient of radiance and the spectral distribution across the sky could provide directional information that T. saltator can potentially use to orient itself during the day even when the sun is not visible (e.g. cloudy sky). The scope of this work was (1) to determine the intensity levels of sky radiance that the sandhoppers use in their zonal recovery and (2) to investigate whether this species relies on the celestial spectral gradient in its zonal recovery. Sandhoppers were tested in the laboratory under artificial radiance or spectral gradients. Our results show that under an artificial sky simulating the natural radiance gradient on a cloudless day, sandhoppers orientated toward the correct seaward direction of their home beach; however, individuals lost their ability to use the intensity gradient as an orientation cue when the radiance was attenuated by at least 40%. Sandhoppers were also able to head in the correct seaward direction of their home beach at any time of the day by using the spectral gradient as their only source of visual orientation reference.