||This paper discusses the influence of light pollution of the night sky on the conditions of visibility of astronomical objects such as planets, stars and comets. This phenomenon has a huge impact on the observability of astronomical objects, especially in cities, where the brightness of the sky makes it difficult or even impossible to conduct astronomical observations. The main purpose of this article is to measure and analyse the surface brightness of the night sky in Rzeszów and its surroundings. A device called the Sky Quality Meter was used to measure the brightness of the night sky. This paper presents measurement results for the years 2015 and 2018, from which it is clear that the quality of the night sky has been deteriorated in terms of the observability of celestial bodies. As an example, the numerical value of the measurement for the centre of Rzeszów has been taken. In 2015, this value was 18.70±1.87 mag/arcsec2, while in 2018, it was equal to 16.73±1.67 mag/arcsec2. The results obtained were used to analyse the visibility of celestial bodies. Here, particular attention was paid to the analysis of the visibility of comets (also during the outburst), in the context of increasing light pollution of the night sky. Observers in neighboring villages have also experienced a change in the sky quality from Bortle Class V to Class VII, requiring objects to be approximately one magnitude brighter in order to be visible.