Newtonian telescope

WordReference Random House Unabridged Dictionary of American English © 2025

Newto′nian tel′escope, 

1. a reflecting telescope in which a mirror or reflecting prism is mounted on the axis near the eyepiece so that the image may be viewed from outside the telescope tube at right angles to the axis.

• 1755–65

Collins Concise English Dictionary © HarperCollins Publishers::

Newtonian telescope noun

1. a type of astronomical reflecting telescope in which light is reflected from a large concave mirror, onto a plane mirror, and through a hole in the side of the body of the telescope to form an image