[n. of agent, in L. form, f. COLLIMATE v.]
1. A small fixed telescope with cross-wires at its focus, used for adjusting the line of collimation of an astronomical or other instrument.
1825. Kater, in Phil. Trans., 147. Description of a floating Collimator.
1843. Rep. Brit. Assoc., 12. Two fixed collimators, watched by levels … enable the observer to determine the position … of the horizontal line.
1885. C. S. Murray, Brit. Almanac & Comp., 120. A collimator … is a telescope furnished with a micrometer at its focus.
1890. Athenæum, 19 April, 494/2. Col. Davidson devised [c. 1855] a collimator for night firing with artillery at a siege.
2. The tube with a slit and lens (or the lens itself) used in the spectroscope to collect the light and throw it upon the prism in parallel rays.
1865. Intell. Observ., No. 36. 389. One-half the slit of the collimator.
1887. Encycl. Brit., XXII. 373. The spectroscope … consists of three parts, the collimator, the prism or grating and the telescope…. The most important adjustment in the spectroscope is that of the collimator.
Comb. 1871. trans. Schellen’s Spectr. Anal., 93. The … ray of light entering the first prism from the slit and collimator-tube.
1887. Encycl. Brit., XXII. 374. The angle subtended by the collimator lens at the slit.
