Lockyer, Norman, Sir, 1836-1920, Seabroke, G. M. (George Mitchell), 1848-1918 · London, Macmillan and co. · leaf 180
na, over which the increasedamount of light, due to greater aperture, is spread;the brightness therefore is not increased, unless indeed we CHAP. XII.] THE MODERN TELESCOPE. 157 were at the first using an unnecessary high power.On the other hand, if we lengthen the focus of theobject-glass, and… … Fig. 82.—Nebula of Oriou. length, and the image on the retina also increases asin the last case. We may, therefore conclude that nocomet or nebula of appreciable diameter, as seen througha telescope having an eyepiece of just such a focallength as to admit all the rays to the eye, can be…
Astronomy · Telescopes
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