The Vienna University Observatory houses one of the most significant collections of historically important scientific books from the 15th to the 19th century. Particularly in the German-speaking world, there are hardly any astronomical libraries with a comparable historically developed collection. The illustrated catalog presents the works from the 15th to the 17th centuries that are represented in this collection, both in text and images. While the primary focus was on the completeness of the bibliographic information and a representative selection of illustrations, the contents of selected works (such as those by G. von Peuerbach, Regiomontanus, Kepler, and others) could also be broken down through historical notes. This sheds new light on the foundational developments of modern astronomy.