Lockyer, Norman, Sir, 1836-1920, Seabroke, G. M. (George Mitchell), 1848-1918 · London, Macmillan and co. · leaf 125
t not perforated, andthe focus of the mirror would be somewhere just in frontof the end of the tube. Now in this case we do notallow the beam to get to the focus at all in the tubeor in front of it ; but before it comes to the focus it is re-ceived on a small diagonal plane surface m, and thus it… … Fig. 55.—Newtons Telescope. The next arrangement is one which Mr. Grubb hasrecently rescued from obscurity, and it is called theCassegrainian form. It will be seen on referring tothat, Fig. 56, if the small mirror, c, were removed, therays from the mirror A b would come to a focus at f. In the…
Astronomy · Telescopes
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