The night sky brightness of Malta

Abstract

Light pollution is the harmful increase in lighting at night as a result of ill-directed and uncontrolled artificial light. In the Maltese Islands, the amount of artificial light at night has significantly increased in the last few years, largely due to unregulated light emissions. The motivation to continue monitoring and quantifying the geographical pattern of the light pollution problem in Malta stems from its adverse effects on numerous fields, including astronomical observation, ecology and human health. In this study, Malta was mapped onto a 1 km2 grid and its light pollution levels were investigated by measuring the night sky brightness in each square using a Unihedron Sky Quality Meter (SQM). It was found that a previously used SQM exhibited a drift due to ageing, so all its measurements were reassessed using a brand new SQM. Analysis on this drift was carried out which showed an apparent trend towards darker skies. With the help of coloured grids and interpolation maps, the general distribution of light pollution in Malta was analysed. The north and west parts of Malta remain dark while the central, east and south areas are severely polluted. Overall, Sliema, Valletta, Marsa, and Birzebbuga, were found to be the most light polluted regions in Malta. Furthermore, the collected data was directly compared to a similar study done in 2017/18 to investigate the change in light pollution levels. Approximately 42% of the areas were found to be brighter in this research, despite the 2017/18 study not adopting an anti-glare hood to block out neighbouring lights. This study brings to the fore the extent of light pollution in Malta, and the importance to regulate its light emissions. Future studies are encouraged to adopt this methodology once again to further identify any new hotspots and problematic areas in Malta and to preserve the few remaining dark skies in our islands.