OBSERVATIONS WITH THE ZENITH TELESCOPE. 



388 



The Constant of Aberration. 



The present series appears to be much better adapted to an investigation of the 

 aberration constant than that of 1889-90. The period covered is from October'10, 1892, 

 to December 27, 1893—443 days. Hence if we assume, in accordance witli Chandler's 

 conclusion, that the latitude variation may be represented by two periodic terms of 12 

 and 14 months respectively, this series will embrace something more than the full term 

 of 14 months. The investigation of this constant formed an important part of the 

 original plan. To this end as many observations as possible were obtained in the 

 morning and evening when the effect of aberration was near the maximum. 



The distribution in Eight Ascension of the 107 pairs of stars was as follows: 



h h 





h h 





/* A 





h h 





0-1 



4 Pairs. 



6- 7 



4 Pairs. 



12-13 



5 Pairs. 



18-19 



5 



1-2 



4 " 



7- 8 



" 



13-14 



3 " 



19-20 



5 



2-3 



4 " 



8- 



5 



14-15 



5 " 



20-21 



5 



3-4 



4 " 



9-10 



4 " 



15-10 



5 



21-22 



4 



4-5 



5 " 



10-11 



4 " 



10-17 



4 " 



22-23 



5 



5-0 



5 " 



11-12 



4 " 



17-18 



4 " 



23-24 



4 



5 Pairs. 



There were in all 1780 observations he tore midnight and 1120 after midnight. 

 We may then write for each observation an equation of the form 



</)„ -| - A - [ ax | N + )' z + l5 "- + '"° + TW = §> 



where cp {) is an assumed value of the latitude, 



A a constant correction to $ , 



ax + (3y terms depending upon the 14 months period, 



y Z _]_ § u terms depending upon the annual period, 



ev correction required on account of erroneous aberration, 



tw secular change in the latitude. 



The longer period was assumed to be 48)0 days as indicated by the interval from 

 maximum to maximum and minimum to minimum of this series in connection with that 

 of 1889-90. The daily change of the argument is therefore 0°.837. 



Let n be the number of days from January 1, 1893, 

 Nz=. 0°.837#, 



O 

 Then 



the sun's true longitude, 



cos N, 



■ wis 0, 



[i = sin N, 

 (5 = sin Q, 



