- a fixed telescope for use in collimating other instruments.
- an optical system that transmits parallel rays of light, as the receiving lens or telescope of a spectroscope.
Examples from the Web for collimator
The slit and collimator are shown; the micrometer end of the observing telescope is out of the picture.The Ether of Space|Oliver Lodge
The slit and lens, together with the tube in which they are usually supported, are called a collimator.A Text-Book of Astronomy|George C. Comstock
The French collimator sight for the 75-millimeter gun presented difficulties to the manufacturer, especially in the optical parts.America's Munitions 1917-1918|Benedict Crowell
The collimator and observing telescope have an aperture of 25 mm., focus of 200 mm.Astronomical Instruments and Accessories|Wm. Gaertner & Co.
The form of spectroscope mentioned above, in which the collimator and slit are replaced by a concave lens, will be tried.