Playing with Geometrical Tools: Johannes Stabius's Astrolabium imperatorium (1515) and Its Successors.

This article suggests that 16th-century sources describing astronomical instruments may be analyzed in terms of 'geometrical tools', that is discrete arrangements of lines and curves that solve particular problems. Geometrical tools provided a means for innovation. By playing, literally, with such tools, mathematicians could invent new instruments or add new functions to existing instruments. For a case study of this process, I shall consider the rectangular astrolabe, first proposed in 1515 by Johannes Stabius and reconfigured in several other versions over the course of the 16th century. Geometrical tools, I conclude, are revealed in diagrams found in the sources, not in the accompanying texts. [ABSTRACT FROM AUTHOR]