| 1. |
(noun) 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 |
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Related Words: optical device |
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| 2. |
(noun) a small telescope attached to a large telescope to use in setting the line of the larger one |
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Related Words: scope, telescope |
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