In scientific documents published in Latin, his common name Krüger (German for potter or innkeeper), was Latinized and spelled Crüger, like e.g. in the case of Nicolaus Copernicus. This distinguishes him from the many other people named Krüger, compared to the few named Crüger.
Crüger then moved to the city of Danzig (Gdańsk) where he worked for the rest of his life as a professor of poetry and mathematics at the Danziger Akademikum (Danzig Academy). As a philosopher and poet, he was associated with the poet Johannes Plavius who in his Institutio Poetica mentions Crüger in its opening letter. Crüger dedicated an extremely laudatory poem to Plavius, which appears in the preface to the Plavius' Praecepta logicalia.
At the time of the Thirty Years War a number of Silesians took refuge from the ravages of war in their towns, among them Andreas Gryphius, who also came for a time to Danzig and was very much influenced by the famous mathematician and astronomer Peter Crüger. Professors Crüger and Mochingert made Gryphius aware of the new style of German-language poetry. Gryphius wrote memorial verses, when in 1638 Crüger's child died. Years ago Crüger had already developed a great friendship with Martin Opitz, "father of German poetry", who also lived in Danzig.
Crüger published treatises on many scientific subjects and contributed to the progress of trigonometry, geography and astronomy, also with the development of astronomical instruments. In the years 1627 to 1630, Crüger was the teacher of a teenager of the Hewelke family who would become known later as Johannes Hevelius, the astronomer. After Hevelius had returned to Danzig in 1634, the dying Crüger appealed to him to pursue astronomy. Hevelius gratefully mentions Crüger in his Machina coelestis.