The heavens above: a popular handbook of astronomy (1882)
Gillet, J. A. (Joseph Anthony), 1837-1908 · New York, Chicago, Potter, Ainsworth, & Co. · leaf 172
Fig. 164. One endof the collimator tubeis seen at the left, andone end of the tele-scope at the right.Sometimes the prismsare made long, andthe light is sent twicethrough the same trainof prisms, once throughthe lower, and once ^^ *• through the upper, half of the prisms. This is accom-plished by…
Astronomy
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