Prof. Encke 07i the Elements oftkePlanet Ceres. 273 



These determinations require, perhaps, a repetition, being 

 calculated with elements which give for the single oppositions 

 places erroneous by fifteen minutes. For this very reason 1 did 

 not deem it necessary to produce a perfect accordance of the ele- 

 ments with the oppositions, but was satisfied with such as gave 

 errors in longitude less than 3". The elements thus deduced, 

 and true for the moment of the epoch, the longitude being re- 

 ferred, for the sake of agreement with the other small planets, 

 to the mean equinox of 1810, are as follows: 



Eleinents of Ceres. 



Mass of Jupiter-^-. 



Epoch 1822. Jan. 22. O*" mean time at Gbttingen. 

 127°36'51"-6) 



147 5Q 57 -G \ Mean equinox 1810. 

 80 41 55 -oj 

 10 38 7-7 

 4 31 18 -0 

 770-72468 (sidereal). 



A rigorous comparison with the geocentric observations at 

 the times of the above four oppositions, has px'esented the fol- 

 lowing differences. 



L = 



w = 

 U = 



4> = 



The two subsequent oppositions of 1827 and 1829 served 



as a test of the accuracy of the elements. For the former one 



N.S. Vol. 7. No. 40. /ipril 1830. 2 N Prof. 



