spherograph

\\ˈsfirəˌgraf, -fer-, -grȧf\ noun

Etymology: sphaer- + -graph

1. : two cardboards used especially in navigation and astronomy, containing various circles, and turning upon each other in such a manner that any possible spherical triangle may be readily found and the measure of the parts read off by inspection

2. : a disk ruled with meridians and parallels in stereographic projection for the solution of problems in spherics