Abstract
THE USE OF A PLANE GRATING IN STELLAR SPECTRO-SCOPY.—In No. 5, vol. vi., of the Journal of the Royal Astronomical Society (Canada) there is an interesting note describing some preliminary tests, made at the Dominion Observatory, Ottawa, of a plane grating used as the dispersion piece of a stellar spectrograph. The grating used is one ruled by Dr. J. A. Anderson, who is now regularly ruling excellent gratings at the Johns Hopkins University, and has a ruled surface of 2/78 × 3/34 in., with 15,000 lines to the inch. It was employed in the Littrow form of spectrograph, giving a linear dispersion of 17·5 Angstroms per millimetre, and gave excellent definition over a nearly flat field extending from λ4800 to λ3500. The photographs secured show a much more uniform intensity over a wide range than do those taken with a three-prism spectrograph, and for this reason will be especially useful. In the red, where the prismatic spectrum is so compressed, and in the violet and ultra-violet, where it suffers considerable absorption, the grating spectrograph will prove very advantageous, and the results of the further experiments to be made will be awaited with interest.
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Our Astronomical Column . Nature 91, 41 (1913). https://doi.org/10.1038/091041a0
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DOI: https://doi.org/10.1038/091041a0