Abstract: Since the invention of electric lighting in the nineteenth century, the steadily increasing use of artificial light at night in outdoor spaces has grown to threaten the integrity of dark night skies and nocturnal terrestrial spaces. The conservation community has gradually come to accept the need to protect natural nighttime darkness, which finds expression in dark sky parks and similar protected areas. As these places begin to reap tangible economic benefits in the form of sustainable ‘astrotourism,’ the movement to actively protect them gains strength. The International Dark-Sky Association designates Dark Sky Parks and Reserves under a comparative ranking scheme that assigns night sky quality tiers according to a combination of objective and subjective characteristics, but shortcomings in the consistency of these ratings exist that undermine the consistency and reputation of the designation program. Here we consider potential changes to the qualification regime to make the ratings system more robust for the benefit of future designations.

Abstract: In this paper we review new available indicators useful to quantify and monitor light pollution, defined as the alteration of the natural quantity of light in the night environment due to introduction of manmade light. With the introduction of recent radiative transfer methods for the computation of light pollution propagation, several new indicators become available. These indicators represent a primary step in light pollution quantification, beyond the bare evaluation of the night sky brightness, which is an observational effect integrated along the line of sight and thus lacking the three-dimensional information.

Abstract: Light pollution is a form of environmental degradation in which excessive artificial outdoor lighting, such as street lamps, neon signs, and illuminated signboards, affects the natural environment and the ecosystem. Poorly designed outdoor lighting not only wastes energy, money, and valuable Earth resources, but also robs us of our beautiful night sky. Effects of light pollution on the night sky can be evaluated by the skyglow caused by these artificial lighting sources, through measurements of the night sky brightness (NSB). The Hong Kong Night Sky Brightness Monitoring Network (NSN) was established to monitor in detail the conditions of light pollution in Hong Kong. Monitoring stations were set up throughout the city covering a wide range of urban and rural settings to continuously measure the variations of the NSB. Over 4.6 million night sky measurements were collected from 18 distinct locations between May 2010 and March 2013. This huge dataset, over two thousand times larger than our previous survey [1], forms the backbone for studies of the temporal and geographical variations of this environmental parameter and its correlation with various natural and artificial factors. The concepts and methodology of the NSN were presented here, together with an analysis of the overall night sky conditions in Hong Kong. The average NSB in Hong Kong, excluding data affected by the Moon, was 16.8 mag arcsec−2, or 82 times brighter than the dark site standard established by the International Astronomical Union (IAU) [2]. The urban night sky was on average 15 times brighter than that in a rural location, firmly establishing the effects of artificial lighting sources on the night sky.