spherograph
noun
sphero·graph
ˈsfirəˌgraf,
-fer-,
-grȧf
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
Word History
Etymology
sphaer- + -graph