The role and significance of illustrations in publications popularising knowledge of astronomy in the second half of the 19th century The article contains an analysis of astronomical iconography in textbooks and popular science books published in 1857–1914 in Poland. The material analysed comprises twenty-nine scientific and popular textbooks by foreign authors as well as original works of Polish popularisers of science. The illustrations used in them served many functions, which corresponded to the publishing needs and were a response to suggestions of social activists and educators in the second half of the nineteenth century. The rich iconographic material makes it possible to follow themes that interested the authors the most as well as the way in which the historical development of the discipline was presented. To this end the illustrations have been divided into several categories, which correspond to the division imposed by the specificity of the sources (“schemata” and elaborate illustrations) and the mode of narration of the popularisers (the Solar System and space outside the System). The analysed publications also generated extreme discussions in the Polish popular science press. The controversy concerned mainly their scientific quality as well as the very need to create this type of literature. Textbook publishers in the second half of the nineteenth century found themselves at a moment of social discussion about the need to familiarise a wider audience with sciences and their impact on the development of everyday life. In the case of astronomy the iconographic material was an indispensable supplement to theoretical knowledge and was part of the trend of popularising science, which reached its peak in the 1870s and 1880s. The development of the science of the stars and the universe at the time could best be followed in textbooks, in which illustrations were one of the most important educational factors.