Sky Glow Research Articles

Embedding sustainability into the design of street lighting

Light pollution is an increasing problem and Artificial Light at Night (ALAN) affects nature in many ways. The Norwegian Road Authorities (SVV) initiated a collaboration with the Norwegian Institute for Bioeconomy (NIBIO) and the University of South-Eastern Norway (USN) to find measures that can help reduce the negative impacts of road lighting on the environment and nature. While USN has looked more generally at sustainable lighting design and ways to reduce the negative effects of road lighting, NIBIO has focused on how road lighting affects insects. We study how the light from roads contributes to light pollution, with the final aim to know more about what measures most effectively reduce the negative effects of road lighting. In this pilot study of light levels in two transects beside a road, the results show that the light levels decreased relatively fast as the distance to the light source increased. Thus, the direct light from the road lighting might not be the most prominent addition to the light pollution in the open landscape. On the other hand, the measurements showed some light influence from the road up to around 160 meters from the road, although the levels were low. While the light was below the detection limit, the light source was visible as a point source at a very large distance. This observation addresses the question of whether organisms are influenced by the average light energy per area, or the intensity of a source as observed from a distance (irradiance vs. radiance). Additional sources of light pollution may affect the result, such as unshielded private light sources and sky glow. This project aims to find measures that can help reduce the negative impacts of road lighting on the environment and nature. We study how the light from roads contributes to different components of light pollution, like skyglow, light trespass and luminance from the light source.

The effect of artificial light at night on a nocturnalprimate.

Anthropogenic disturbance is a major threat to biodiversity. An anthropogenic disturbance that is rarely addressed for nonhuman primates is the effect of artificial light at night (ALAN) which is defined by the spread of artificial lighting at night which eliminates natural darkness. Artificial light at night can result from streetlights, or indirectly from sky glow (artificial light that is scattered and reflected back to earth by the atmosphere). Research has demonstrated that artificial lighting causes changes in animal behavior, reproductive success, survivorship, as well as can alter the composition of the communities. The goal of this paper is to explore how the behavior of spectral tarsiers, Tarsius spectrumgurskyae, is modified in response to artificial light. We conducted this study at Tangkoko Nature Reserve on the easternmost tip of the northern arm of Sulawesi, Indonesia. The results of this study suggest that in response to artificial light tarsiers increase their time spent travelling and foraging, left their sleeping sites earlier and returned to them later thereby extending their daily activity time. The tarsiers also left their sleeping trees at lower heights, gave fewer vocalizations and fewer alarm calls each night in response to the additional artificial light. The tarsier's lengthened night might be leading to a change in interspecific competition for food as well as increase the ability of potential predators to locate the tarsiers. Additional research on the effect of ALAN on primates is clearly needed.

Uniform sky glow observed through the throat of a wormhole

Uniform sky glow observed through the throat of a wormhole

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'.

Does artificial light at night alter moth community composition?

Ecological studies investigating the effects of artificial light at night (ALAN) have primarily focused on single or a few species, and seldom on community-level dynamics. As ALAN is a potential cause of insect and biodiversity declines, community-level perspectives are essential. We empirically tested the hypothesis that moth species differentially respond to ALAN and that these responses can cause shifts in community composition. We sampled moths from prairie fragments in Colorado, USA. We tested whether local light sources, sky glow, site area and/or vegetation affected moth community diversity. We found that increased sky glow decreased moth abundance and species richness and shifted community composition. Increased sky glow shifted moth community composition when light and bait traps were combined; notably this result appears to be driven entirely by moths sampled at bait traps, which is an unbiased sampling technique. Our results show that ALAN has significant effects on moth communities and that local light sources have contrasting effects on moth community composition compared to sky glow. It is imperative that we better understand the contrasting effects of types of ALAN to comprehend the overall impacts of light pollution on biodiversity declines. This article is part of the theme issue 'Light pollution in complex ecological systems'.

UBVRI night sky brightness at Kottamia Astronomical Observatory

Photoelectric observations of night sky brightness (NSB) at different zenith distances and azimuths, covering all the sky, at the Egyptian Kottamia Astronomical observatory (KAO) site of coordinates ϕ = 29° 55.9′ N and λ = 31° 49.5′ E, were done using a fully automated photoelectric photometer (FAPP). The Bessel wide range system (UBVRI) is used for the first time to observe NSB for three consecutive nights (1–3 August, 2022) under good seeing conditions after the moon sets. The deduced results were taken in photons and converted into mag/arcsec2. The average zenith sky brightness for U, B, V, R and I filters are found to be 20.49, 20.38, 19.41, 18.60 and 17.94 mag/arcsec2 respectively. The average color indices (U–B), (B–V), (V–R) and (R–I), at the zenith are detected to be 0.11, 0.98, 0.81 and 0.66, respectively. We plotted the isophotes of the sky brightness at KAO in U, B, V, R and I colors (filters) and determined both the average atmospheric extinction and sky transparency through these UBVRI filters. The atmospheric and other meteorological conditions were taken into our consideration during the observational nights. The results of the current study illustrate the main impact of the new cities built around KAO on the sky glow over it, and which astronomical observations are affected.

Towards Material Digitization with a Dual-scale Optical System

Existing devices for measuring material appearance in spatially-varying samples are limited to a single scale, either micro or mesoscopic. This is a practical limitation when the material has a complex multi-scale structure. In this paper, we present a system and methods to digitize materials at two scales, designed to include high-resolution data in spatially-varying representations at larger scales. We design and build a hemispherical light dome able to digitize flat material samples up to 11x11cm. We estimate geometric properties, anisotropic reflectance and transmittance at the microscopic level using polarized directional lighting with a single orthogonal camera. Then, we propagate this structured information to the mesoscale, using a neural network trained with the data acquired by the device and image-to-image translation methods. To maximize the compatibility of our digitization, we leverage standard BSDF models commonly adopted in the industry. Through extensive experiments, we demonstrate the precision of our device and the quality of our digitization process using a set of challenging real-world material samples and validation scenes. Further, we demonstrate the optical resolution and potential of our device for acquiring more complex material representations by capturing microscopic attributes which affect the global appearance: we characterize the properties of textile materials such as the yarn twist or the shape of individual fly-out fibers. We also release the SEDDIDOME dataset of materials, including raw data captured by the machine and optimized parameteres.

Sensitivity studies of nighttime top-of-atmosphere radiances from artificial light sources using a 3-D radiative transfer model for nighttime aerosol retrievals

Abstract. By accounting for surface-based light source emissions and top-of-atmosphere (TOA) downward lunar fluxes, we adapted the spherical harmonics discrete ordinate method (SHDOM) 3-dimensional (3-D) radiative transfer model (RTM) to simulate nighttime 3-D TOA radiances as observed from the Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band (DNB) on board the Suomi-NPP satellite platform. Used previously for daytime 3-D applications, these new SHDOM enhancements allow for the study of the impacts of various observing conditions and aerosol properties on simulated VIIRS-DNB TOA radiances. Observations over Dakar, Senegal, selected for its bright city lights and a large range of aerosol optical depth (AOD), were investigated for potential applications and opportunities for using observed radiances containing VIIRS-DNB “bright pixels” from artificial light sources to conduct aerosol retrievals. We found that using the standard deviation (SD) of such bright pixels provided a more stable quantity for nighttime AOD retrievals than direct retrievals from TOA radiances. Further, both the mean TOA radiance and SD of TOA radiances over artificial sources are significantly impacted by satellite viewing angles. Light domes, the enhanced radiances adjacent to artificial light sources, are strong functions of aerosol properties and especially aerosol vertical distribution, which may be further utilized for retrieving aerosol layer height in future studies. Through inter-comparison with both day- and nighttime Aerosol Robotic Network (AERONET) data, the feasibility of retrieving nighttime AODs using 3-D RTM SHDOM over artificial light sources was demonstrated. Our study shows strong potential for using artificial light sources for nighttime AOD retrievals, while also highlighting larger uncertainties in quantifying surface light source emissions. This study underscores the need for surface light emission source characterizations as a key boundary condition, which is a complex task that requires enhanced input data and further research. We demonstrate how quality-controlled nighttime light data from the NASA's Black Marble product suite could serve as a primary input into estimations of surface light source emissions for nighttime aerosol retrievals.

Impact of urban air pollutants on the night sky brightness and color in Hohhot

This study investigated the impact of urban air pollutants on the brightness and color of the night sky in Hohhot, China. The study used correlation analysis to determine the relationship between air pollutant concentrations and night sky brightness. Observations were conducted using a charge-coupled device(CCD) camera and an unmanned aerial vehicle (UAV) to assess changes in night sky brightness, color, and their spatial distribution before and after the aggravation of air pollution. The results revealed that particulate matter (PM) had the strongest correlation with night sky brightness among urban air pollutants, while the correlation between gaseous pollutants (except O3) and night sky brightness needs to be cautiously interpreted. The CCD camera observations showed that the night sky shifted toward red as the concentration of urban air pollutants increased. Meanwhile, the UAV observations demonstrated that the brightness of the night sky decreased with height above ground, and the area of night sky glow increased with higher urban air pollutant concentrations. Based on the research findings, controlling air pollutant emissions may have a positive impact on reducing the level and area of light pollution in the night sky, and thus promote sustainable urban environment development.

Dark roads aid movement but increase mortality of a generalist herbivore in the American Southwest

AbstractRoad networks pose many well‐documented threats to wildlife, from fragmenting habitats and restricting movement to causing mortality through vehicle collisions. For large, wide‐ranging mammals, home range requirements and seasonal migrations often necessitate road crossings, posing threats to human safety, property, and animal survival. Artificial nightlight, emanating from light posts and urban sky glow, is ubiquitous on and around road networks worldwide; however, its effects on road crossing behavior and the associated mortality risk for wildlife are not well understood. By integrating the latest NASA nightlight products with GPS collar data collected from 67 mule deer (Odocoileus hemionus) over a 7‐year period (2012–2018), we used a resource‐selection framework to assess factors influencing seasonal crossing behavior and road mortality in Salt Lake City, Utah, an expanding metropolitan area in the United States. We found deer preferred to cross the road where surrounding artificial nightlight was lower in both summer and winter seasons, especially during crepuscular and nighttime periods. However, lower nightlight levels also increased the risk of road mortality. Areas with more shrub cover and lower speed limits increased the likelihood of crossing as well as lowered the risk of road mortality. There were five times as many mortality events in winter as in summer, likely because of the combination of deer preference for dark roads mixed with proximity to both higher speed roads and increased human activity. Better understanding how a pervasive and expanding environmental pollutant like artificial nightlight may attract or repel human‐tolerant wildlife species from roadways presents an opportunity to mitigate collision risk while improving population management strategies for this abundant, generalist herbivore and many other economically and ecologically important species.

Specifying Non-White Light Sources in Outdoor Applications to Reduce Light Pollution

ABSTRACT Anthropogenic (“human-generated”) light at night (ALAN) from outdoor lighting produces light pollution and as a result causes a range of deleterious responses in humans, plants, and animals. An emerging strategy to combat light pollution, especially sky glow, is to use “amber” LEDs in lieu of phosphor-converted white LEDs with high correlated color temperatures. Importantly, however, there is no standardized terminology or chromaticity designation that is applicable to “amber” LED lighting products for outdoor illumination. In this work, we propose a specification structure for light sources with nonstandard chromaticities to increase the precision of language used in the architectural lighting industry and demonstrate that light sources with well-defined chromaticity ranges outside of the ANSI C78.377–2017 quadrangles may be useful for reducing the portion of relative sky glow related to light source spectral power distribution. We encourage lighting standards development organizations to consider standardizing such a system.

Sky glow disrupts the orientation of Australian flatback turtles Natator depressus on nesting beaches

Sky glow disrupts the orientation of Australian flatback turtles Natator depressus on nesting beaches

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.

Amber is not yet the white knight for sustainable outdoor light

Non-white light (NWL), and specifically yellow-orange or amber light sources, are often posed as a solution for environmentally sensitive areas and for astronomical sky glow. Lighting requirements published by various institutions ranging from public advocacy groups to governmental regulators demonstrate little agreement on NWL spectral thresholds and metrics. A recent market and performance analysis of NWL policies and products found that current international guidelines are not aligned, the terminology currently used by the lighting industry is inconsistent, and NWL LED products would likely not meet performance requirements for luminaire efficacy or colour rendition set by existing certification bodies.

NIGHT TIME CLOUDS DETECTION ABOVE PERMATAPINTAR OBSERVATORY USING ALL-SKY IMAGERY

We proposed a method to detect clouds in a suburban class night sky for the larger purpose of astronomical site testing. A 'threshold criterion' approach was adopted to discriminate between the pixels representing the foreground clouds from the pixels representing the background sky in a single all-sky image. This method was developed based on all-sky images captured at the PERMATApintar Observatory (PpO) in Selangor (2°55'02" N, 101°47'17" E), where the night sky has been categorised as a suburban class night sky. The night sky conditions were divided into three categories depending on the cloud cover: clear, partially cloudy, and overcast skies. Samples of all-sky images for each night sky condition were selected and respective histogram images were generated. These samples were then used to inductively derive the threshold criterion based on the skewness and peak values of the image's histogram. This sky/cloud threshold will enable pixels representing foreground clouds to be discriminated from the pixels representing the background sky under each type of night sky conditions. Our work found that the night sky over PpO requires two thresholds to accurately distinguish between cloud and sky pixels due to the sky glow effect. The first threshold is based on the peak value of the image's histogram. If an image's histogram has a peak value ≥ 80, then the image is considered a clear sky. Otherwise, the image is considered cloudy or overcast sky if the peak value is < 80.

Correspondence: Obtrusive light, light pollution and sky glow: Areas for research, development and standardisation

Correspondence: Obtrusive light, light pollution and sky glow: Areas for research, development and standardisation

Optical space communication. Review

Features of information exchange between satellites and satellites with ground stations and in the opposite direction are considered. The influence of such atmospheric factors as fog, rain, snow, atmospheric turbulence, background noise, and sky glow on the quality of information signals is analyzed. The expediency of using transmitter frequencies, which lie in the area of windows of the Earth transparency and are in the infrared region of the spectrum, has been established. In particular, generators of such frequencies in the near-infrared region can be InGaAs laser diodes, which are light in the region of about 1550 nm, and in the far-infrared region – cascade lasers, which are able to generate radiation in the range of 3.5 to 24 μm. InGaAs photodiodes and HgCdTe detectors should be used as receivers of the mentioned frequencies.

Instrument assessment and atmospheric phenomena in relation to the night sky brightness time series

Several networks of Sky Quality Meters show long-term trends in measuring the night sky brightness. Causes of this variation could be ageing of the instruments and variations of the sky emission. The data from Ekar Observatory (Italy) are here considered.No significant ageing effect was detected on 9-year-old housing windows. A 9-year-old IR blocking filter shows a variation of its spectral transmittance up to 80%.No trend on the SQM output was found due to only the variation of the spectral distribution of the night sky emission. Together with ageing of the IR blocking filter, it causes a reduction of the SQM output of about 0.01magSQMarcsec-2 per year.Slow trend of the aerosol optical depth suggests the air near the considered site is changing towards less polluted conditions. It reduces scattering of the artificial light and consequently sky glow in the light polluted considered site.

The effect of natural and artificial light at night on nocturnal song in the diurnal willie wagtail

Artificial light at night (ALAN) has rapidly and drastically changed the global nocturnal environment. Evidence for the effect of ALAN on animal behaviour is mounting and animals are exposed to both point sources of light (street and other surrounding light sources) and broadscale illuminance in the form of skyglow. Research has typically taken a simplified approach to assessing the presence of ALAN, yet to fully understand the ecological impact requires consideration of the different scales and sources of light concurrently. Bird song has previously been well studied for its relationship with light, offering an opportunity to examine the relative impact of different sources of light on behaviour. In this study, we combine correlational and experimental approaches to examine how light at night affects the nocturnal song behaviour of the largely diurnal willie wagtail (Rhipidura leucophrys). Observations of willie wagtails across urban and rural locations in southeastern Australia demonstrated that nocturnal song behaviour increased with the intensity of moonlight in darker rural areas but decreased in areas with high sky glow. In addition, willie wagtails were half as likely to sing at night in the presence of localized light sources such as streetlights in urban and rural areas. Experimental introduction of streetlights to a previously dark area confirmed this relationship: willie wagtail song rates declined when lights were turned on and returned to their original rates following streetlight removal. Our findings show that scale, as well as intensity, are important when considering the impact of light at night as moonlight, sky glow, and localized sources of artificial light have different effects on nocturnal song behaviour.

Areas of ecological importance are exposed to risk from urban sky glow: Auckland, Aotearoa-New Zealand as a case study

Areas of ecological importance are exposed to risk from urban sky glow: Auckland, Aotearoa-New Zealand as a case study