10 letters · 14 points in Scrabble
noun a small telescope attached to a large telescope to use in setting the line of the larger one
noun optical device consisting of a tube containing a convex achromatic lens at one end and a slit at the other with the slit at the focus of the lens; light rays leave the slit as a parallel beam
originEtymology tree English collimate English -or English collimator From collimate + -or.
Etymology from Wiktionary, CC BY-SA 3.0