Lessons in astronomy including uranography. A brief intoductory course without mathematics (1896)
Young, Charles A. (Charles Augustus), 1834-1908 · Boston, London, Ginn and company · leaf 127
116 GREAT SUN SPOT. [§164 operations, since an object-glass which would give admirableresults for visual purposes would be worthless photograph- … Fig. 28.—The Great Sun Spot of September, 1870, and the Structure of the Photo-sphere. From a Drawing by Professor Langley. From the New Astronomy, bypermission of the Publishers. ically. Since 1890, however, a few object glasses have beenmade with new kinds of glass, which are said to be good…
Astronomy
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