A text-book of general astronomy : for colleges and scientific schools (1888)
Young, Charles A. (Charles Augustus), 1834-1908 · Boston ; London : Ginn & Company · leaf 65
Fig. 28. — The Filar Position-Micrometer. … Fig. 29.—Construction of the Micrometer. other set run north and south. This position angle is read on agraduated circle, which forms part of the instrument. Means ofillumination are provided, giving at pleasure either dark wires in abright field, or vice versa. With this instrument one can measure…
Astronomy
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