Star-land : being talks with young people about the wonders of the heavens (1891)
Ball, Robert S. (Robert Stawell), Sir, 1840-1913 · London ; Paris : Cassell & Co. · leaf 234
eur astronomer has completed this part ofthe task, all the great difficulties about his telescope areconquered. The tube may be made of wood, and, indeed, asquare tube will do just as well as a round one. He mustalso provide for the top of the tube a small mirror, whichhas to be perfectly flat. The… … Fig. 68.—The GrindingTool. 2 2 o St A r-La nd . will touch all over ; then they will certainly all be flat.One more part you want, and that is an eye-piece. Thispresents no difficulty. A single glass lens can be made toanswer, and your telescope is complete. THE DISCOVERY OF URANUS. It is now more…
Astronomy
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