collimator

nouns

a small telescope attached to a large telescope to use in setting the line of the larger one
is derived from
is a type of (narrower)
a magnifier of images of distant objects
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
is a part of
an optical instrument for spectrographic analysis
is a type of (narrower)
a device for producing or controlling light