Abstract
STELLAR PARALLAX.—The results of a series of observations with the filar micromerer on the Washington refractor for the determination of the annual parallax of a Lyræ and 61 Cygni have been printed in advance of the publication of the yearly volume of observations. The measures were made by Prof. Asaph Hall, those of α Lyræ extending from May 24, 1880, to July 2, 1881, on seventy-seven nights, and those of 61 Cygni from October 24, 1880, to December 7, 1881, on sixty-six nights. The magnifying power employed was 383. Prof. Hall remarks that since observations of the angle of position made with the micrometer-circle are less accurate for distances that enter into the determination of parallax, he observed simply the difference of declination of α Lyræ and the companion of the tenth magnitude, and in the ewe of 61 Cygni the difference of declination of the smaller component and a star of 9·5 magnitude about 3′·3 south of the double star, which is D.M. + 38 °, No. 4345. α Lyræ was obseived both with bright and dark wires, for 61 Cygni only the dark wires were used. It may be noted that the star measured is the following component of the double star. The course of observation pursued for each night's set of measures is describ d, and except on one occasion the same programme was followed throughout.
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OUR ASTRONOMICAL COLUMN . Nature 27, 210 (1882). https://doi.org/10.1038/027210a0
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DOI: https://doi.org/10.1038/027210a0