PART I. 



CATALOGUE POSITIONS OF THE 

 STANDARD STARS. 



Catalogues and Weights. 



For the reduction of stellar photographs it is necessary that 

 the positions of certain stars on the plate be known as accu- 

 rately as possible. Such stars are designated in the following as 

 standards. When I undertook the measurement and reduction 

 of the Rutherfurd Photographs of the Cluster in Coma Berenices, 

 the problem arose to determine such standards. 



There was no sufficiently accurate set of meridian observa- 

 tions available. Chase's triangulation of the cluster, made at 

 the Yale Observatory, 1891-1892,^ includes a number of my 

 stars, and these I might have used as standards. But results 

 obtained by the heliometer are not always reliable ; that is to say, 

 although the relative positions are in general very accurate, the 

 group as a whole may show a large systematic error. This was 

 to be feared in the present case, as the absolute positions of the 

 stars of the cluster were made to depend ultimately on but two 

 points, determined by meridian observations. Aside from this 

 Consideration, Chase gives a very good authority from which to 

 obtain the proper motions of those stars common both to his 

 work and to the Rutherfurd photographs. Motion of the group 

 as a whole would, however, be eliminated, were his star places 



' "Triangulation of the Principal Stars of the Cluster in Coma Berenices," by 

 Frederic L. Chase. Transactions of the Astronomical Observatory of Yale Univer- 

 sity. Referred to as Chase. 



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