The Collaborative International Dictionary
finder scope
Finder \Find"er\, n.
One who, or that which, finds; specifically (Astron.), a small telescope of low power and large field of view, attached to a larger telescope, for the purpose of finding an object more readily, called also a finder telescope or finder scope.
(Micros.) A slide ruled in squares, so as to assist in locating particular points in the field of vision.