The collimator and observing telescope have an aperture of 25 mm., focus of 200 mm.
The slit and lens, together with the tube in which they are usually supported, are called a collimator.
The French collimator sight for the 75-millimeter gun presented difficulties to the manufacturer, especially in the optical parts.
The slit and collimator are shown; the micrometer end of the observing telescope is out of the picture.
The form of spectroscope mentioned above, in which the collimator and slit are replaced by a concave lens, will be tried.
A device that turns incoming radiation, such as light, into parallel beams. Simple collimators consists of a tube having a narrow, variable slit at one end and a convex lens at the other. Radiation entering the tube through the slit exits the lens in the form of parallel beams. Collimators are used to establish focal lengths of lenses and to measure the distance of distant objects whose position is known. See illustration at spectroscope.