ASTRONOMY AND MATHEMATICS. 



ASTRONOMY. 



No. 5. BURNHAM, S. W. General Catalogue of Double Stars within 121 of the 



North Pole. Quarto, 2 vols. Published 1906. Price $14.00. 

 Vol. 1. The Catalogue, LV-j-256 (256a-256r) pages. 

 Vol.2. Notes to the Catalogue, vm+257-1086 pages. 



A catalogue of all the double stars visible in the northern hemisphere, discovered 

 since the earliest records, with all the measures and other observations from Her- 

 schel in the seventeenth century to the latter part of 1906. In volume 1 the stars 

 are given in order of right ascension, in tabular form, in eleven columns, giving 

 respectively the general number, the name of the double star, a reference to one of 

 the principal star catalogues in which the star is found, the right ascension, the 

 declination, the measured position-angle, the measured distance, the magnitudes of 

 the components, the date of the measures given, the observer and number of ob- 

 servations, and lastly brief notes concerning colors, etc. The first portion of this 

 volume contains some fifty pages of introductory matter, including ten indexes to 

 the various observers, classes of stars, etc., enabling the user to find at once any 

 special star, or class of star, without a knowledge of the star places. Volume 2 

 contains the notes and complete references to all the observations of each of the 

 13,665 double stars. All published orbits of the binary systems and the proper- 

 motions of the brighter stars are given. The history of each pair includes a selec- 

 tion of the best measures showing motion, if any, and an examination of the mate- 

 rial questions suggested by the measures. Some 600 diagrams, drawn to exact scale, 

 show the relative change in the systems having decided orbital and proper motions. 



No. 168. BURNHAM, S. W. Measures of Proper Motion Stars. Quarto, iv+311 

 pages. Published 1913. Price $4.00. 



Micrometer measures made with the large telescope of the Yerkes Observatory 

 from 1907 to 1912 of various stars having large, small, or uncertain proper-motions. 

 These selected stars are of all magnitudes from the faintest in Argelander to prom- 

 inent naked-eye stars, and include, as far as possible, all those which have been 

 heretofore compared by direct measures with other and fainter stars in the field. 

 Independent differential values of the proper-motions are thus obtained for com- 

 parison with the results found from meridian observations. The latter values are 

 frequently discordant and contradictory, and particularly so when the motions are 

 small. The several values from the leading authorities on meridian-circle observa- 

 tions, Auwers, Newcomb, Porter, Boss, etc., and from the various standard star 

 catalogues, are collected and compared. The greater number of proper-motion 

 stars observed here are taken from the General Catalogue of Double Stars. The 

 others are selected from various sources and include stars of special interest, among 

 others the Boss group of Taurus stars with a common movement in space, and 

 small stars with supposed proper-motions taken from the Oxford and other astro- 

 graphic catalogues. As a rule each star is measured on three or more nights, and 

 very faint comparison-stars selected which, it is safe to say, have no sensible motion 

 which could affect the result obtained. No really faint star, not attached to and 

 moving with a brighter star, has ever been shown to have any proper-motion which 

 could be detected by any method of observation to this time. Of course it is to be 

 presumed that the faintest and most distant stars have both proper-motion and 

 parallax, and it is equally obvious that the one is as negligible as the other in all 

 differential comparisons. A careful remeasurement of these small stars after a 

 suitable interval of time will give the movement of the principal stars with a degree 

 of accuracy not yet attained by other methods. 



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