 | Simon Newcomb - 1878 - 592 Seiten
...disadvantage of this arrangement is that Fio. 86.—Herschellun telescope. the rays cannot be brought to an exact focus when they are thrown so far to one side of the axis, and the injury to the definition is so great that the front-view plan is now entirely abandoned. The... | |
 | 1881 - 612 Seiten
...advantage — so thoroughly appreciated by those in the habit of observing for many consecutive hours^of allowing the observer always to look downward, its...bring the rays to an exact focus when they are thrown VAN NOSTRAND8 ENGINEERING MAGAZINE. BO far to one side of the axis of the tube; and the injury to definition,... | |
 | Joseph Anthony Gillet - 1882 - 496 Seiten
...front - view telescope. The great disadvantage of this arrangement is, that the rays cannot be brought to an exact focus when they are thrown so far to one side of the axis, and the injury to the definition is so great that the frontview plan is now entirely abandoned. The... | |
 | Thomas Nolan - 1904 - 188 Seiten
...rs. As it falls between rs and its principal focus, a second, and enlarged, image is formed at o'J'. While the Herschelian has the brightest image of all...front view " plan has been almost entirely abandoned. c. which is formed in the axis OT, is a small concave mirror CD. T is, with regard to CD, as an object... | |
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... at o'b'. While the Herschelian has the brightest image of all the reflecting telescopes, with a given aperture, and possesses the advantage — so thoroughly appreciated by those in the habit of observing for many consecutive hours — of allowing... 