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Light pollution is one of the most rapidly increasing types of environmental degradation. To limit this pollution several effective practices have been defined: shields on lighting fixtures to prevent direct upward light; no over lighting, i.e. avoid using higher lighting levels than strictly needed for the task, constraining illumination to the area where and when it is needed. Nevertheless, even after the best control of the light distribution is reached and when the proper quantity of light is used, upward light emission remains, due to reflections from the lit surfaces and atmospheric scatter. The environmental impact of this "residual light pollution" cannot be neglected and should be limited too. We propose a new way to limit the effects of this residual light pollution on wildlife, human health and stellar visibility. We performed analysis of the spectra of common types of lamps for external use, including the new LEDs. We evaluated their emissions relative to the spectral response functions of human eye photoreceptors, in the photopic, scotopic and melatonin suppressing bands finding that the amount of pollution is strongly dependent on the spectral characteristics of the lamps, with the more environmentally friendly lamps being low pressure sodium, followed by high pressure sodium. Most polluting are the lamps with a strong blue emission, like white LEDs. Migration from the now widely used sodium lamps to white lamps (Metal Halide and LEDs) would produce an increase of pollution in the scotopic and melatonin suppression bands of more than five times the present levels, supposing the same photopic installed flux. This increase will exacerbate known and possible unknown effects of light pollution on human health, environment and on starry sky visibility. We present quantitative criteria to evaluate the lamps based on their spectral emissions and we suggest regulatory limits.

Light pollution is a worldwide problem that has a range of adverse effects on human health and natural ecosystems. Using data from the New World Atlas of Artificial Night Sky Brightness, VIIRS-recorded radiance and Gross Domestic Product (GDP) data, we compared light pollution levels, and the light flux to the population size and GDP at the State and County levels in the USA and at Regional (NUTS2) and Province (NUTS3) levels in Europe. We found 6800-fold differences between the most and least polluted regions in Europe, 120-fold differences in their light flux per capita, and 267-fold differences in flux per GDP unit. Yet, we found even greater differences between US counties: 200,000-fold differences in sky pollution, 16,000-fold differences in light flux per capita, and 40,000-fold differences in light flux per GDP unit. These findings may inform policy-makers, helping to reduce energy waste and adverse environmental, cultural and health consequences associated with light pollution.

Artificial lights raise night sky luminance, creating the most visible effect of light pollution-artificial skyglow. Despite the increasing interest among scientists in fields such as ecology, astronomy, health care, and land-use planning, light pollution lacks a current quantification of its magnitude on a global scale. To overcome this, we present the world atlas of artificial sky luminance, computed with our light pollution propagation software using new high-resolution satellite data and new precision sky brightness measurements. This atlas shows that more than 80% of the world and more than 99% of the U.S. and European populations live under light-polluted skies. The Milky Way is hidden from more than one-third of humanity, including 60% of Europeans and nearly 80% of North Americans. Moreover, 23% of the world's land surfaces between 75{\deg}N and 60{\deg}S, 88% of Europe, and almost half of the United States experience light-polluted nights., Comment: 26 pages, 19 figures, 3 tables

We apply the sky brightness modelling technique introduced and developed by Roy Garstang to high-resolution DMSP-OLS satellite measurements of upward artificial light flux and to GTOPO30 digital elevation data in order to predict the brightness distribution of the night sky at a given site in the primary astronomical photometric bands for a range of atmospheric aerosol contents. This method, based on global data and accounting for elevation, Earth curvature and mountain screening, allows the evaluation of sky glow conditions over the entire sky for any site in the World, to evaluate its evolution, to disentangle the contribution of individual sources in the surrounding territory, and to identify main contributing sources. Sky brightness, naked eye stellar visibility and telescope limiting magnitude are produced as 3-dimensional arrays whose axes are the position on the sky and the atmospheric clarity. We compared our results to available measurements., Comment: 14 pages, 12 figures, accepted for publication in MNRAS, 17 june 2004

We present the first World Atlas of the zenith artificial night sky brightness at sea level. Based on radiance calibrated high resolution DMSP satellite data and on accurate modelling of light propagation in the atmosphere, it provides a nearly global picture of how mankind is proceeding to envelope itself in a luminous fog. Comparing the Atlas with the U.S. Department of Energy (DOE) population density database we determined the fraction of population who are living under a sky of given brightness. About two thirds of the World population and 99% of the population in US (excluding Alaska and Hawaii) and EU live in areas where the night sky is above the threshold set for polluted status. Assuming average eye functionality, about one fifth of the World population, more than two thirds of the US population and more than one half of the EU population have already lost naked eye visibility of the Milky Way. Finally, about one tenth of the World population, more than 40% of the US population and one sixth of the EU population no longer view the heavens with the eye adapted to night vision because the sky brightness., Comment: 24 pages, 11 size-reduced PostScript figures, 3 statistical tables, accepted for publication in Monthly Notices of the Royal Astronomical Society, high-resolution original maps will be available soon from http://www.lightpollution.it/dmsp/ as zipped TIFF files

We extend the method introduced by Cinzano et al. (2000a) to map the artificial sky brightness in large territories from DMSP satellite data, in order to map the naked eye star visibility and telescopic limiting magnitudes. For these purposes we take into account the altitude of each land area from GTOPO30 world elevation data, the natural sky brightness in the chosen sky direction, based on Garstang modelling, the eye capability with naked eye or a telescope, based on the Schaefer (1990) and Garstang (2000b) approach, and the stellar extinction in the visual photometric band. For near zenith sky directions we also take into account screening by terrain elevation. Maps of naked eye star visibility and telescopic limiting magnitudes are useful to quantify the capability of the population to perceive our Universe, to evaluate the future evolution, to make cross correlations with statistical parameters and to recognize areas where astronomical observations or popularisation can still acceptably be made. We present, as an application, maps of naked eye star visibility and total sky brightness in V band in Europe at the zenith with a resolution of approximately 1 km., Comment: 15 pages, 8 size-reduced PostScript figures, accepted for publication in Monthly Notices of the Royal Astronomical Society, high-resolution original maps will be available as zipped TIFF files from http://www.pd.astro.it/cinzano/page93.html

We present a method to map the artificial sky brightness across large territories in astronomical photometric bands with a resolution of approximately 1 km. This is useful to quantify the situation of night sky pollution, to recognize potential astronomical sites and to allow future monitoring of trends. The artificial sky brightness present in the chosen direction at a given position on the Earth's surface is obtained by the integration of the contributions produced by every surface area in the surrounding. Each contribution is computed based on detailed models for the propagation in the atmosphere of the upward light flux emitted by the area. The light flux is measured with top of atmosphere radiometric observations made by the Defense Meteorological Satellite Program (DMSP) Operational Linescan System. We applied the described method to Europe obtaining the maps of artificial sky brightness in V and B bands., Comment: 17 pages, 14 PostScript figures, mn.sty, accepted for publication in Monthly Notices of the Royal Astronomical Society

We present the map of the artificial sky brightness in Europe in V band with a resolution of approximately 1 km. The aim is to understand the state of night sky pollution in Europe, to quantify the present situation and to allow future monitoring of trends. The artificial sky brightness in each site at a given position on the sky is obtained by integration of the contributions produced by every surface area in the surroundings of the site. Each contribution is computed taking into account based on detailed models the propagation in the atmosphere of the upward light flux emitted by the area and measured by the Operational Linescan System of DMSP satellites. The modelling technique, introduced and developed by Garstang and also applied by Cinzano, takes into account the extinction along light paths, a double scattering of light from atmospheric molecules and aerosols, Earth curvature and allows to associate the predictions to the aerosol content of the atmosphere., Comment: 8 pages, 6 PostScript figures, paspconf.sty, to appear in IAU-UN Symposium 196 "The Protection of the Astronomical Sky"

We present a project to map the artificial sky brightness in Europe in the main astronomical photometrical bands with a resolution better than 3 km. The aim is to understand the state of night sky pollution in Europe, to quantify the present situation and to allow future monitoring of trends. The artificial sky brightness in each site at a given position on the sky is obtained by the integration of the contributions produced by every surface area in the surroundings of the site. Each contribution is computed taking in account the propagation in the atmosphere of the upward light flux emitted by the area and measured from DMSP satellites. The project is a long term study in which we plan to take in account successively of many different details in order to improve the maps. We present, as a preliminary result, a map of the V-band artificial sky brightness in Italy in 1998 and we compare it with the map obtained 27 years earlier by Bertiau, Treanor and De Graeve. Predictions for the artificial sky brightness within the next 27 years are also shown., Comment: 9 pages, 3 PostScript figures, memsait.sty; poster presented at the XLIII Meeting of Italian Astron. Soc.; Proceedings will be in Mem. Soc. Astron. It