01 n. A telescope arranged and used to determine errors of collimation, both vertical and horizontal.
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1.
A telescope arranged and used to determine errors of collimation, both vertical and horizontal.(Astron.)
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2.
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.(Optics)