Interference of Meteorological Variables on Night Sky Observation in Rural and Urban Zones of South-Western Spain

Abstract

Several factors affect the visibility of the night sky, most significantly artificial light at night (ALAN), meteorological conditions and Moon illumination. There are few studies that analyse the effect of meteorological conditions and Moon illumination, especially in rural areas (where the ALAN level is lower). An analysis of these variables could be relevant for sky observation, especially for astronomical observatories, usually located in rural areas with low ALAN. Knowledge of the relevant variables in the observation allows for the correct planning of the observation. The observer can consult meteorological agencies for forecasts of these variables, allowing him to know in advance whether the observation will be carried out under optimal conditions. In this study, a photometer and a weather station were installed in various municipalities located in rural areas of south-western Spain. This equipment was also installed in the city of Badajoz (urban area with high ALAN). These devices carried out simultaneous measurements of night sky darkness (NSB) and meteorological conditions for a period of approximately 6 months. A statistical analysis of the recorded data was carried out. Only the Moon illumination was slightly correlated with NSB in both cases (−0.3 in rural areas and −0.35 in urban areas). Sky temperature only proved a correlation with NSB in the urban area (−0.41). The correlations indicated are significant at the 0.01 level. The results obtained in the urban area were confirmed by a second analysis using meteorological data provided by a meteorological agency, obtaining similar results. A web application was developed that allows for real-time consultation of NSB and meteorological data for each area, which can help observe the starry sky. Globally, the results obtained in this study could help in the planning of stargazing in both urban and rural areas, allowing one to know in advance if weather conditions would affect the perception capacity.