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Webster 1913 Edition
Collimator
Col′li-maˊtor
,Noun.
1.
(Astron.)
A telescope arranged and used to determine errors of collimation, both vertical and horizontal.
Nichol.
2.
(Optics)
A tube having a convex lens at one end and at the other a small opening or slit which is at the principal focus of the lens, used for producing a beam of parallel rays; also, a lens so used.