The heavens above: a popular handbook of astronomy (1882)
Gillet, J. A. (Joseph Anthony), 1837-1908 · New York, Chicago, Potter, Ainsworth, & Co. · leaf 43
principle this is thesame with the Gregorian ; but the small mirror, R, is con-vex, and is placed inside the focus, F, so that the rays arereflected from it before reaching the focus, and no imageis formed until they reach the opening in the large mirror.This form has an advantage over tlie… … Optically these forms of telescope are inferior to theNewtonian ; but the latter is subject to the inconvenience,that the observer must be stationed at the upper end ofthe telescope, where he looks into an eye-piece screwedinto tlie side of the tube. ASTRONOMY. 25 On the other hand, the…
Astronomy
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