. Elements of astronomy: accompanied with numerous illustrations, a colored representation of the solar, stellar, and nebular spectra, and celestial charts of the northern and the southern hemisphere. ont of onehalf of the slit. This light is usually obtained from theinduction-spark taken between electrodes of differentmetals, raised to incandescence by the passage of an in-duced electric current. 491. What is shown by an examination of the spectrum of a Orionis? 492. Towhat is the star-spectroscope attached ? In the arrangement adopted, what is thefirst thing done ? Describe the other parts o
. Elements of astronomy: accompanied with numerous illustrations, a colored representation of the solar, stellar, and nebular spectra, and celestial charts of the northern and the southern hemisphere. ont of onehalf of the slit. This light is usually obtained from theinduction-spark taken between electrodes of differentmetals, raised to incandescence by the passage of an in-duced electric current. 491. What is shown by an examination of the spectrum of a Orionis? 492. Towhat is the star-spectroscope attached ? In the arrangement adopted, what is thefirst thing done ? Describe the other parts of the arrangement. Through whatis the spectrum viewed? How is the light which is to be compared with thestar-spectrum received? How is this light iisually obtained? 493. Describe the CELESTIAL PHOTOGKAPHY. 271 493. A very powerful Spectroscope was for some timeused at the Kew Observatory, in England, for mapping thesolar spectrum. The light enters at a narrow slit in oneof the collimators, which is furnished with an object-glassat the end next the prism, to render the rays parallel be-fore they enter the prisms. In the passage through theprisms the ray is bent into a circle, widening out as it. 494. It is often convenient to use what is termed aDirect-vision Spectroscope—that is, one in which the light enters and leaves theprisms in the same straightline. How this is man-aged in the Herschel- Fig. 102.—Path op the Eat in the Heb- ° * # . schel-bbowning Spectboscope. one of the best of its kind,by means of successive refractions and reflections, may begathered from Fig. 102. 495. Celestial Photography.—In both telescopic andspectroscopic observations, the visible rays of light areused. The chemical rays, however, being also present,photographs of the brighter celestial objects can be taken;and celestial photography, in the hands of Mr. De La Rueand Mr. Rutherford, has been brought to a high state ofperfection. The method adopted is to place a sensitiveplate in the focus o
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectastronomy, bookyear18
