An enhanced version of the Gaia map of the brightness of the natural sky

The natural night sky brightness is a relevant input for monitoring the light pollution evolution at observatory sites, by subtracting it from the overall sky brightness determined by direct measurements. It is also instrumental for assessing the expected darkness of the pristine night skies. The natural brightness of the night sky is determined by the sum of the spectral radiances coming from astrophysical sources, including zodiacal light, and the atmospheric airglow. The resulting radiance is modified by absorption and scattering before it reaches the observer. Therefore, the natural night sky brightness is a function of the location, time, and atmospheric conditions. We present in this work the GAia Map of the Brightness Of the Natural Sky (GAMBONS), a model to map the natural night brightness of the sky in cloudless and moonless nights. Unlike previous maps, GAMBONS is based on the extra-atmospheric star radiance obtained from the Gaia catalogue. The Gaia-Data Release 2 (DR2) archive compiles astrometric and photometric information for more than 1.6 billion stars up to G = 21 mag. For the brightest stars, not included in Gaia-DR2, we have used the Hipparcos catalogue instead. After adding up to the star radiance the contributions of the diffuse galactic and extragalactic light, zodiacal light and airglow, and taking into account the effects of atmospheric attenuation and scattering, the radiance detected by ground-based observers can be estimated. This methodology can be applied to any photometric band, if appropriate transformations from the Gaia bands are available. In particular, we present the expected sky brightness for V (Johnson), and visual photopic and scotopic passbands.

We reanalyze the Imaging Photopolarimeter data from Pioneer 10 to study the zodiacal light in the B and R bands beyond Earth orbit, applying an improved method to subtract integrated star light (ISL) and diffuse Galactic light (DGL). We found that there exists a significant instrumental offset, making it difficult to examine the absolute sky brightness. Instead, we analyzed the differential brightness, i.e., the difference in sky brightness from the average at high ecliptic latitude, and compared with that expected from the model zodiacal light. At a heliocentric distance of r < 2 au, we found a fairly good correlation between the J-band model zodiacal light and the residual sky brightness after subtracting the ISL and DGL. The reflectances of the interplanetary dust derived from the correlation study are marginally consistent with previous works. The zodiacal light is not significantly detectable at r > 3 au, as previously reported. However, a clear discrepancy from the model is found at r = 2.94 au which indicates the existence of a local dust cloud produced by the collision of asteroids or dust trail from active asteroids (or main-belt comets). Our result confirms that the main component of the zodiacal light (smooth cloud) is consistent with the model even beyond the earth orbit, which justifies the detection of the extragalactic background light after subtracting the zodiacal light based on the model.

view Abstract Citations (89) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Upper limit on the extragalactic background light. Dube, R. R. ; Wickes, W. C. ; Wilkinson, D. T. Abstract An experiment to determine the brightness of the extragalactic background light at 5115 A is described. The separate contributions to the night sky brightness from several sources are eliminated or measured independently. Light from discrete sources (stars and resolved galaxies) is blocked from the photometer by a telescope focal-plane mask; the zodiacal light is measured using its Fraunhofer spectrum; airglow and atmospheric scattered light are determined by their zenith-angle dependence. The remaining sky brightness of 1.0 + or - 1.2 S(10) is attributed to the extragalactic background light plus a possible diffuse galactic component. An attempt to detect the latter by analysis of the galactic-latitude dependence of the sky brightness was inconclusive, so the result may be interpreted only as an upper limit on the extragalactic light of 3.4 S(10) at the 90% confidence level. Publication: The Astrophysical Journal Pub Date: September 1979 DOI: 10.1086/157292 Bibcode: 1979ApJ...232..333D Keywords: Background Radiation; Extraterrestrial Radiation; Galactic Evolution; Light (Visible Radiation); Airglow; Astronomical Photometry; Cosmology; Focal Plane Devices; Fraunhofer Lines; Sky Brightness; Zodiacal Light; Astrophysics; Background Radiation; Background Radiation:Cosmology full text sources ADS |

The light of the night sky consists of atmospheric components (airglow, light scattered in the atmosphere) and – even in the case of spaceborne observations – of zodiacal, galactic and extragalactic light. Although all components are of similar importance, investigations on zodiacal light have profitted most by the space age since their object of research, the interplanetary dust cloud, became accessible to direct in-situ measurements. Lunar samples and measurements by micrometeoroid detectors provide individual and eventually detailed information on impact events, which however are limited in number and therefore restricted in statistical significance. Zodiacal light investigations involve scattered light of many particles in large volume elements and therefore provide global information about physical properties and spatial distribution of interplanetary dust grains, however just in terms of average values. Therefore both sources of information are complementary and a synthesis can only be achieved by synoptic interpretation of zodiacal light, micrometeoroid, and meteoroid investigations also including dynamical aspects. Measurements of zodiacal light (and emission) from rockets, manned or non manned spacecraft, and deep space probes gained drastically in importance compared to ground based observations. On the other hand investigations on airglow have become more and more a topic of geophysics Caeronomy). They remain relevant however to astronomy as far as photometric features are concerned. These general trends continued in the last triennium and have influenced the activities of our commission.

The light of the night sky consists of atmospheric components (airglow, light scattered in the atmosphere) and - even in the case of spaceborne observations - of zodiacal, galactic and extragalactic light. Although all components are of similar importance, investigations on zodiacal light have profitted most by the space age since their object of research, the interplanetary dust cloud, became accessible to direct in-situ measurements. Lunar samples and measurements by micrometeoroid detectors provide individual and eventually detailed information on impact events, which however are limited in number and therefore restricted in statistical significance. Zodiacal light investigations involve scattered light of many particles in large volume elements and therefore provide global information about physical properties and spatial distribution of interplanetary dust grains, however just in terms of average values. Therefore both sources of information are complementary and a synthesis can only be achieved by synoptic interpretation of zodiacal light, micrometeoroid, and meteoroid investigations also including dynamical aspects. Measurements of zodiacal light (and emission) from rockets, manned or non manned spacecraft, and deep space probes gained drastically in importance compared to ground based observations. On the other hand investigations on airglow have become more and more a topic of geophysics (aeronomy). They remain relevant however to astronomy as far as photometric features are concerned. These general trends continued in the last triennium and have influenced the activities of our commission.

The brightness of the night sky at an astronomical site is one of the principal factors that determine the quality of available optical observing time. At any site the optical night sky is always brightened with airglow, zodiacal light, integrated starlight, diffuse Galactic light and extra-galactic light. Further brightening can be caused by scattered sunlight, aurorae, moonlight and artificial sources. Dome C exhibits many characteristics that are extremely favourable to optical and IR astronomy; however, at this stage few measurements have been made of the brightness of the optical night sky. Nigel is a fibre-fed UV/visible grating spectrograph with a thermoelectrically cooled 256 × 1024 pixel CCD camera, and is designed to measure the twilight and night sky brightness at Dome C from 250 nm to 900 nm. We present details of the design, calibration and installation of Nigel in the AASTINO laboratory at Dome C, together with a summary of the known properties of the Dome C sky.

The night sky brightness has an ecological impact, especially for nocturnal animals. Likewise, the shift from transition night to day and vice versa known as the fajr/dawn phase, has on impact on crepuscular animals. Continuous measurement are important in astronomy due to the impact of sky brightness. The sky brightness is slower to lighten at dawn and slower to darken at dusk which can be affected by light pollution sourced from human activities, meteorological, and natural factors (Moon phase and zodiacal light). Quantization of the sky brightness continuously in full days based on the function of light pollution, Sun position, and shadow length in the daytime are important to do. Analysis of the sky brightness at the limits of the beginning of dawn, the end of dusk, the sunrise/sunset, during mid-morning/evening, and the time of culmination are useful for testing the Islamic prayers time. Measurement of sky brightness in full days has been done using Sky Quality Meter photometer at coordinates 6˚50’42” southern latitude and 109˚37’55” eastern longitude for 25 days with 3 seconds retrieval resolution that installed neutral density variable and battery. Analysis of sky brightness data was carried out using Difference, Moving average, and Polynomial methods. This research concludes that the sky brightness during twilight shows relatively small variation, with the beginning of dawn identified at -15.301˚ of Sun elevation and the end of dusk at -18.853˚ of Sun elevation. The sky brightness profiles before and after 12 noon are asymmetrical. In the evening, the average difference in sky brightness at shadow lengths of 1 to 2 is 0.9 MPSAS with 0.39 standard deviation and the average shadow length of object during fluctuations is 1.36. The average difference in sky brightness at noon compared to midnight is 9.02 MPSAS.

The morning and evening twilight brightness are important to probe the properties of the upper atmosphere. We conducted a short survey of broad band twilight sky brightness measurements by using a portable photometer with 5 second resolution, in five places with different elevations. The darkest zenith sky brightness reached 22.9 MPASS. We found the complex twilight sky brightness variation and proposed 17 degree solar dip for Fajr prayer. The observable young crescent moon which has less than 24 hours in age has the sky brightness at the range of 8-16 magnitude/arcsec 2 . These correspond to telescope visual limiting magnitude of 2.9 to 9.3. The excellent quality of telescope is needed for this purpose to cope with very low contrast of young crescent moon. Keywords : twilight, sky brightness, fajr prayer, young crescent moon. 1. Introduction The sky brightness refers to the residual light that is present in the night sky during dark, moonless nights and becomes one of the parameters for observing location. It poses a major source of noise for ground-based astronomical observations, and good astronomical sites

We present the near-infrared observation of the zodiacal light with the IRTS (Infrared Telescope in Space), a small cryogenically cooled orbital infrared telescope. The observed spectra of the sky brightness at wavelengths from 1.4 μm to 4.0 μm are characterized by a smooth stellar-like spectrum at wavelengths shorter than 3.2 μm, and enhanced emission at the long wavelengths, which is attributed to thermal emission from interplanetary dust (IPD). The measured sky brightness has a clear dependence on the ecliptic latitude, implying that the zodiacal light is a dominant emission component of the near-infrared sky. The spectrum of the zodiacal light, itself, was obtained by subtracting other emission components. Although it is fairly close to the solar spectrum at wavelengths between 1.8 and 3.2 μm, it clearly shows a decrement in the scattering efficiency at the short-wavelength end. The zodiacal light at 1.4–3.2 μm is about twice as bright as that extrapolated from optical measurements. These results indicate that large dust is responsible for the near-infrared zodiacal light; they also suggest that the IPD that has a spectral reflectance similar to the S-type asteroids could be responsible for the near-infrared zodiacal light.

Anthropogenic sky glow (a result of light pollution) combines with the natural background brightness of the night sky when viewed by an observer on the earth’s surface. In order to measure the anthropogenic component accurately, the natural component must be identified and subtracted. A model of the moonless natural sky brightness in the V-band was constructed from existing data on the Zodiacal Light, an airglow model based on the van Rhijn function, and a model of integrated starlight (including diffuse galactic light) constructed from images made with the same equipment used for sky brightness observations. The model also incorporates effective extinction by the atmosphere and is improved at high zenith angles (>80°) by the addition of atmospheric diffuse light. The model may be projected onto local horizon coordinates for a given observation at a resolution of 0.05° over the hemisphere of the sky, allowing it to be accurately registered with data images obtained from any site. Zodiacal Light and integrated starlight models compare favorably with observations from remote dark sky sites, matching within ± 8 nL over 95% of the sky. The natural airglow may be only approximately modeled, errors of up to ± 25 nL are seen when the airglow is rapidly changing or has considerable character (banding); ± 8 nL precision may be expected under favorable conditions. When subtracted from all-sky brightness data images, the model significantly improves estimates of sky glow from anthropogenic sources, especially at sites that experience slight to moderate light pollution.

The mid-infrared spectrum of the zodiacal and exozodiacal light

The Diffuse Infrared Background Experiment (DIRBE) aboard the Cosmic Background Explorer (COBE)1 mapped the entire sky redundantly in 10 wavebands at 1.25, 2.2, 3.5, 4.9, 12, 25, 60, 100, 140, & 240 μm. The scattering or thermal emission from interplanetary dust contributes significantly to the sky brightness in all 10 wavebands, dominating most. The sky brightness is modulated in time due to the changing viewing aspect of the DIRBE line of sight through the interplanetary dust cloud. A three‐dimensional semi‐physical model for the distribution, emission, and scattering of interplanetary dust was optimized to match the time‐dependence of the sky brightness as observed by DIRBE. The method and results of this fitting procedure are described, as are the difficulties and some future prospects for disentangling the zodiacal light from other contributions to the diffuse infrared sky brightness.

ABSTRACTThe radiance of sky brightness differs principally with wavelength passband. Atmospheric scattering of sunlight causes the radiation in the near-infrared band. The Antarctic is a singular area of the planet, marked by an unparalleled climate and geographical conditions, including the coldest temperatures and driest climate on Earth, which leads it to be the best candidate site for observing in infrared bands. At present, there are still no measurements of night-sky brightness at DOME A. We have developed the Near-Infrared Sky Brightness Monitor (NISBM) in the J, H, and Ks bands for measurements at DOME A. The instruments were installed at DOME A in 2019 and early results of NIR sky brightness from 2019 January–April have been obtained. The variation of sky background brightness with solar elevation and scanning angle is analysed. The zenith sky flux intensity for the early night at DOME A in the J band is in the 600–1100 μJy arcsec−2 range, that in the H band is between 1100 and 2600 μJy arcsec−2, and that in the Ks band is in the range ∼200–900 μJy arcsec−2. This result shows that the sky brightness in J and H bands is close to that of Ali in China and Mauna Kea in the USA. The sky brightness in the Ks band is much better than that in Ali, China and Mauna Kea, USA. This shows that, from our early results, DOME A is a good site for astronomical observation in the Ks band.

We provide radiometric evidence of the relevance of nearby light sources on the artificial brightness of the night sky. To obtain the required data we developed a method based on the use of power-regulated urban lighting systems, which also provides relevant information on the propagation of light pollution at short distances from the sources. A controlled experiment was carried out in the Andalusian municipality of Añora (1526 inhab.) in which the radiant power of its regulated public outdoor lighting system was modified in a predefined way during the central part of the night while continuously recording the zenith sky brightness in the TESS-W photometric band from two separate locations inside the town. We determined that the power-regulated streetlight sources contribute a 60–62% to the total zenith sky brightness at these observing locations in clear and moonless nights when operated at their maximum power rating, being the remaining sky radiance due to constant local sources and sources from neighboring towns. These results, in combination with georeferenced information on the sources' location and properties, impose some constraints on the functional form of the effective point-spread functions (PSF) of the zenith sky brightness at short distances from the sources. For the conditions of our experiment we have found that the expected exponents of power-law PSFs are close to -1.

Measurements performed at San Benito Mountain during 1976-87 reveal that the zenith sky brightness in the V and B photometric bands is well correlated with the solar 10.7-cm radio flux, and thus with the intensity of the solar EUV radiation in the 100-625 A range. It is found that the brightness of the zenith sky decreases exponentially by about 0.4 mag in both V and B during at least the first half of the night. The results indicate that the level of solar EUV flux and the time of night must be taken into account when assessing the quality of a dark-sky site.