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VI.—The Solar Spectrum at Medium and Low Altitudes. Observations of the Region between Wave-Lengths 6024 and 4861 Å.U., made at Lord Crawford's Observatory, Dun Echt, during the Years 1887 to 1889

Published online by Cambridge University Press:  17 January 2013

Ludwig Becker
Affiliation:
Temporary Second Assistant-Astronomer, Royal Observatory, Edinburgh.

Extract

At the end of 1886 a method occurred to me of rapidly recording the positions of the lines of the solar spectrum, which I thought might be used with advantage for determining the faint “Telluric dry-gas lines” near D, mentioned in Professor Piazzi Smyth's maps of The Visual Solar Spectrum in 1884. The fundamental idea of the recording apparatus is that of magnifying by some mechanical means the motion of the grating, or prism, to such an extent that it can be recorded on a continuous fillet of paper. The viewing telescope being then firmly clamped, the exact positions of the grating can be pricked off on the strip of paper as the lines are successively brought to the fixed cross in the field of view.

For the satisfactory use of the method two conditions suggest themselves as desirable. First, the punctures should not be less than a good-sized pin hole, and the interval between the closest lines, which the spectroscope is able to separate, should be represented on the paper strip by a space of several tenths of an inch.

Type
Research Article
Copyright
Copyright © Royal Society of Edinburgh 1892

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References

page 99 note * Trans. Roy. Soc. Edin., vol. xxxii. part 3.

page 101 note * Upsal, 1868.

page 101 note † Trans. Roy. Soc. Edin., vol. xxxii. part 3.

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page 119 note * Laplace, , Traité de mécanique celeste, Tome iv. livre x. p. 246. Paris, 1805Google Scholar.

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page 134 note 1 M. Thollon's maps, which we have just received (see Postscript), give water-vapour lines in the α-group, the middle of the band being in = 1586. Each of the first three bands of the series is thus followed by a group of lines which are fainter than the bands themselves.

page 134 note 2 The Catalogue begins on p. 48.

page 135 note 1 The maps have been reproduced by photo-lithography, and are about one-fourth of the size of the original drawings. It will be noticed that the faintest lines are far from continuous in the lithographs, but as it was found impracticable to make good this defect without altering the breadth of the lines, they are left untouched.

page 135 note 2 Paris, 1890.

page 137 note 1 On p. A15, loc. cit., there is a table of water-vapour lines in which the figures do not agree with those given above. M. Thollon gives 107 telluric lines more than we counted from the book. We reproduce his summary:—