Young, Charles A. (Charles Augustus), 1834-1908, Young, Anne Sewell, b. 1871., ed · Boston, New York [etc.] Ginn and Company · leaf 440
on of the reading micro-scopes seen at A, B, C, and D, by means of which the circle isread. For these, see works on Practical Astronomy. 549. Zero Points. — The instrument is used to measure thealtitude or else the polar distance of a heavenly body at the time 420 APPENDIX. [§549 when it is… … Fig. 154. — A Meridian Circle. The polar point is determined by taking the circle readingfor some star near the pole when it crosses the meridian abovethe pole, and then doing the same thing again twelve hourslater when it crosses it below. The mean of the two readings,corrected for refraction,…
Astronomy · Constellations
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