ANNALS 



OF TFI?; 



NEW YORK ACADEMY OF SCIENCES, 



VOLUME VIII. LiBR.A^v 



NEW ' 



no* 



I. — The Parallaxes of n and 9 C'assiopeiee, deduced from 

 Rulherfurd Photographic Measures. 



BY HAROLD JACOBY. 



Read Jan. 9, 1803. 



The Rutherfurd photographic measures of the stars surround- 

 ing IX Cassiopeiae are derived from twenty-eight negatives made 

 between 1870 July, and 1873 December. These observations were 

 taken in accordance with Rutherfurd's regular plan for securing 

 accurate micrometrie measures of star clusters: but in order to 

 combine therewith a determination of parallax, the observations 

 were all made in the months of July, January, and December. 

 There are two impressions upon each negative. A discussion of 

 all the micrometrie measures of some fifty-six stars will be published 

 later, the present paper containing those measures only that have 

 been selected for the parallax determination. I have set down in 

 table I. (p. 12) the dates and other details of the several exposures, 

 so far as they are connected with the present purpose. The sidereal 

 time given is the mean of the four instants marking the beginning 

 and ending of the two exposures. The second exposure always 

 began a few seconds after the ending of the first, and the duration 

 of each was six minutes. 



Table II. (p. 13) gives a list of the comparison stars employed. 

 The pair g, h, will not furnish a suitable parallax factor in distance, 

 Annals N. Y. Acad. Sci., VIII, March, 1893.— 1 



