Newcomb, Simon, 1835-1909 · New York, H. Holt & company · leaf 91
ASTRONOMICAL INSTRXIMENTB. '73 The instrument can be used as a transit to determine right ascensions, as before described. It can be also used to measure declinations in the following way : If the telescope is pointed to the nadir, a certain diyision of … Fig. 25. the circles, as N, is under the first microscope. We can make the nadir a yisible point by placing a basin of quick- silver below the telescope and looking in it through the tel- escope. AYe shall see the wires of the reticle and also their
Astronomy
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