PHOTOGRAPHIC RESEARCHES NEAR THE POLE OF THE HEAVENS. 



6 



very successful 



and 



8 stars situated within about one 



of the pole. There are 28 measurable images of each 



But 



order to try a practical example without too 

 have contented ourselves with determining y 



delay 

 refully 



we 



distributed images of ten stars, or 60 images in all. 



The 



were made with one of the Repsold machines of the Columbia University 

 observatory. The method of measurement by position angles and distances 

 was employed, because the images are slightly elongated in the direction of 



diurnal 



the 



As this direction makes 

 e, considerable personal 



vary 



by attempting to refer the images directly to the 



ig angle with the reseau 

 mid have been introduced 

 reseau lines. Each image 

 was independently measured in two positions by two observers, Miss F. E. 



_ mm 



Harp ham and Miss K. U. Peirce. All the customary precautions were taken 

 to eliminate instrumental errors, and they included a careful determination 

 of the departure from straightness of the microscope slide, upon which the 

 precision of the position angles depends. Passing over the details of these 

 investigations, we give in the following little Table the general data for the 

 reduction of the plate. 



General Data for the Reduction of the Plate. 



Sid. Time 



Barom. 

 Therm. R. 

 Log k cot q> 



Jmage 1. 



20 A 43'"47?9 



mm 



750 . 2 



1.54237 



Image 6 



23 / '13'"50f3 



mm 



749.7 



2?0 

 1.54387 



Image 11. 



l A 43 7W 62f7 



mm 



749 . 5 



1.54474 



Image 17. 



4* 1 3'"54 f 8 



mm 



748.8 



2?95 



1.54524 



Image 22. 



6*48 B, 66?8 



mm 



748.3 



3?35 



1.54576 



Image 28. 



9*13 M 68!7 



mm 



748.2 



1.54580 



the next Table are given the measured coordinates, corrected for 



and dependin 



of the two observers. As 



gin we have taken the point which happened to coincide with the 

 of rotation of the position circle of the machine. 



The distances 



and the nosition angles are oriented 



ward 0° right ascension at 

 Star 10 is X Ursae Minoris 



of the first exposure (Compare 



•W.-1U*. ctj. 61. 



21 



