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MM11EPAT0PCK0M AKAAEMIM 



(Bulletin de TAcad^mie Imperiale des Sciences de St.-P^tersbourg 



1898. Juin. T. IX, Xs 1.) 



Photographic Researches near the Pole of the 



Heavens. 



By Harold Jacoby. 



(Read the 18-th march 1898). 



CONTENTS. 



Page. 



1. Reduction of Polar Photographs 41 



2. Trail Plates. . 51 



3. Example of the Reduction of a Trail Plate 60 



4. A Method of Determining the Constants of Aberration, 



Nutation and Precession . . 77 



5. Conclusion 82 







1. Reduction of Polar Photographs. 



When it is desired to compute the places of stars near the pole of the 

 heavens from their positions measured on photographic plates, it is conve- 

 nient to make use of methods different from those generally employed for 

 other parts of the sky. The present paper contains the formulas which seem 

 to me most suitable. I shall assume that the positions of the star-images on 



the plate have been measured with 



rectangular coordi 



nates, and that the measures have been fully corrected for all the errors of 

 division and other errors of the measuring machine. In other words, I shall 



that 



possession of a set of 



rectangular coordinates 

 [ in a uniform scale of 



of the star-images, such coordinates 



equal parts. It is unnecessary that the absolute length of such scale be 



known, but it is important that the scale be exactly the same for the two 



coordinates. 



Let us define the optical axis of the telescope as a line drawn through 

 the object glass and normal to all its surfaces. I shall assume that the plate 

 is mounted in the tube so as to be truly perpendicular to the 

 of the telescone. and that the uoint 





axis 



where that axis pierces the plate is 



known. This point will then be taken as the origin of the measures of 

 dinates on the nlate. 



*H3.-MaT. CTJ. 41. 



I 



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