Carnegie Institution of Washington Publication Volume 138

Carnegie Institution of Washington Publication Volume 138

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1911 edition. Excerpt: ...e a irect compar f th l '.. ' graphs the third Order has been WIOI1 d e p ates as regards quality and. definition.. For these Photo xperiments have shown that the total variation at the bottom of th1S " corresponding to a daily range inside the spectroscope house of about 150 C. can hardly exceed 0706 C. It is scarcely possible that the grating can have worked under conditions approaching this in excellence when i.ii the horizontal spectrographin the Snow telescope house. The effect of small variations of temperature in the grating during an exposure will eventually be to widen the lines slightly without, in the case of dinerential determinations of this sort, introducing errors into the displacements, since both spectra are affected alike. The accidental errors of measurement will, however, be somewhat greater for the wider lines, and this is no doubt partly accountable for the gain in the intemal agreement of the measures on the later plates. The procedure followed in taking the plates differs little from that used in the earlier series, and so does not require very extended consideration. The fact that the spectrograph itself is rotated to obtain the position.angle settings for the various latitudes desired has made it possible to secure on all of the plates a position corresponding to the projection of the sun's pole on its visible edge, and this has been used as a most important check on the results for the successive exposures. It constitutes very marked advantage which the later plates possess over those of the earlier series. The reference line for the observations is obtained by securing the transits of the sun's image across the 30.inch position circle on the top of the...show more

Product details

  • Paperback | 26 pages
  • 189 x 246 x 1mm | 68g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236912055
  • 9781236912053