A text-book of general astronomy : for colleges and scientific schools (1888)
Young, Charles A. (Charles Augustus), 1834-1908 · Boston ; London : Ginn & Company · leaf 193
any desiredgradation may be obtained by settingit at the proper angle, without theuse of a shade-glass. 288. It may be asked why itwill not answer merely to cap the object-glass, and so cut offpart of the light, instead of re-jecting it after it has once beenallowed to enter the telescope. It is… … FlG. B3. — Polarizing Helioscope. PHOTOGRAPHY. 181 aperture, therefore, is to sacrifice the definition of delicate details.With a low power there is no objection to reducing the amount ofheat admitted into the telescope tube in that way, but with the higherpowers the whole aperture should always be…
Astronomy
Internet Archive · Wellesley College Library · Public Domain Mark 1.0. Free to use for anything.
