Astronomy for the use of schools and academies (1882)
Gillet, J. A. (Joseph Anthony), 1837-1908, Rolfe, W. J. (William James), 1827-1910 · New York : Potter, Ainsworth, & Co. · leaf 40
Fig. 25. James Gregory, who probably preceded Newton as an in-ventor of the reflecting telescope. Behind the focus, F(Fig. 26), a small concave mirror, R, is placed, by whichthe light is reflected back again down the tube. The largermirror, M, has an opening through its centre ; and the… … Fig. 26. The Cassegrainian Reflector. — In 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…
Astronomy
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