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1. A small telescope attached to a large telescope to use in setting the line of the larger one
    
2. Optical device consisting of a tube containing a convex achromatic lens at one end and a slit at the other with the slit at the focus of the lens; light rays leave the slit as a parallel beam

Derived forms: collimators

See also: collimate

Type of: optical device, scope, telescope

Part of: prism spectroscope, spectroscope

Encyclopedia: Collimator