Astronomy for the use of schools and academies (1882)
Gillet, J. A. (Joseph Anthony), 1837-1908, Rolfe, W. J. (William James), 1827-1910 · New York : Potter, Ainsworth, & Co. · leaf 173
:;7V^ : SltfL … image of the micrometer scale alongside the image of thespectrum. 150. The Comparison of Spectra. — In order to com- ASTRONOMY. 155 pare two spectra, it is desirable to be able to see them side by side in the telescope. The images of two spectra may be obtained side by side in the telescope tube by…
Astronomy
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