Measuring Light Pollution in the Night Sky – From Technology Demonstrator to Monitoring System

Pollution of the night sky by artificial light has now become an important element of the modern city landscape. The decline in the quality of the sky observed at night in urban areas has already been noticed even by residents unaware of its origin. A starry sky is nowadays not easy to observe even in places far from large conurbations or smaller cities. More and more places are losing access to the previously natural privilege of observing the dark sky, and their inhabitants are thus systematically exposed to all the direct and indirect negative effects of this phenomenon. Monitoring the brightness of the night sky is gaining interest from a growing number of interdisciplinary research groups being established around the world, including Poland. In Toruń, the first measurements of the magnitude of this phenomenon, together with the determination of its spatial scale, were started using handheld devices in 2017. In the following years, efforts were made to improve the data acquisition process by creating a prototype – a technology demonstrator and, consequently, a commercial version of an automatic device measuring the surface brightness of the night sky. This paper presents the stages of the project aimed at developing a light pollution monitoring system, which has been consistently implemented in Toruń. The most important component of this system is a measuring device of our own design and construction. The monitoring system designed and operating in Toruń, starting in 2019, is being further developed with new components and monitoring (measurement) sites being systematically added, making the city’s observation network increasingly dense. The devices built using the LoRa standard for wireless data exchange implement the concept of the Internet of Things, fitting in with the objectives of a smart city.