The elements of astronomy; a textbook . Fig. 44. — Telescope and Fig. 45.— Herschel Eye-Piece. wider its image of a sharp line. fore, to sacrifice the definition of delicate details. The simplest, and a very good one,is known as Herschels, in which thesuns rays are reflected at right anglesby a plane of unsilvered glass (). With this apparatus, althoughthe reflected light is still too intensefor the unprotected eye, only a thinshade glass is required, and it doesnot become much heated. It is nota good plan to cap the object-glassin order to cut off part of the smaller
The elements of astronomy; a textbook . Fig. 44. — Telescope and Fig. 45.— Herschel Eye-Piece. wider its image of a sharp line. fore, to sacrifice the definition of delicate details. The simplest, and a very good one,is known as Herschels, in which thesuns rays are reflected at right anglesby a plane of unsilvered glass (). With this apparatus, althoughthe reflected light is still too intensefor the unprotected eye, only a thinshade glass is required, and it doesnot become much heated. It is nota good plan to cap the object-glassin order to cut off part of the smaller the object-lens of thetelescope, the larger the image itmakes of a luminous point, or the To cut down the aperture is, there- 183. Photography. — In the study of the suns surface, pho-tography is for some purposes very advantageous and muchused. The instrument must, however, have lenses speciallyconstructed for photographic operations, since an object-glasswhich would give admirable results for visual purposes wouldbe worthless photographically, and vice versa (see
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Keywords: ., bookcentury1900, bookdecade1910, booksubjec, booksubjectastronomy
