[ 384 ] 



XLT. 



OBSEBVATIONS OF THE LATE CONJUNCTION OF MAES 

 AND SATUEN. By MAJOE SOMEESET MAXWELL, 

 F.E.A.S. 



[Read December 18, 1889.] 



On the 20th September, 1889, I was fortunate enough to be 

 enabled to observe the conjunction of the planets Mars and 

 Saturn, under tolerably favourable conditions, at my Observatory 

 in the Co. Cavan, 



Lat. 53° 49' 30", 



Long. W. 11 29 m 13 s . 



Although clouds were frequent they were not continuous; and 

 the intervals of brightness were of sufficient duration to admit of 

 a fairly satisfactory series of micrometrical determinations of 

 position and distance. 



The instrument used was a 6-inch refractor, with bifilar 

 micrometer by Sir Howard Grrubb, and the time was taken (with 

 the help of an assistant) from a watch which was compared, 

 both before and after the observations, with a chronometer, the 

 error of which latter was obtained the same day at 3.30 p.m. by 

 a mean of five sextant altitudes of the sun. 



Taking into consideration the unfavourable position of the 

 planets (their altitude being from 20° to 30°), the rapidity with 

 which the change, both in position angle and distance, took 

 place, and the frequent interruption by clouds, I deemed it 

 advisable not to attempt the precautions usually taken to secure 

 an accurate result : such, for instance, as measuring on different 

 sides of the central wire, and on alternate limbs of the planets, 

 but to content myself with single measurements whenever I could 

 get them. 



The measurements thus obtained, corrected for semi-diameter, 

 are shown in the third and fourth columns of the following table, 

 the fifth of which represents the value of the distance measures 

 corrected for parallax and refraction : — 



