An instrument used to measure small angles, diameters, and distances of heavenly bodies.
·noun An instrument, used with a telescope or microscope, for measuring minute distances, or the app...
Webster's Dictionary of the English Language
An instrument necessary for delicate astronomical measurements. It contains vertical and horizontal ...
The Sailor's Word-Book
Has one of its lenses divided, and separable to a certain distance by a screw, which at the same tim...