42 CELESTIAL MECHANICS: LEUSCHNER 



(128) NEMESIS 



Discovered by Watson 1 at Ann Arbor on November 25, 1872, and 

 also by Borrelly 2 at Marseilles on December 4, 1872. 



Preliminary Elements A were computed by Bossert, 3 based on obser- 

 vations 1872, November 25, December 7, and December 22. He also 

 published a short search ephemeris. 



Preliminary Elements B based on observations covering the first 

 five months were published 4 by Leo de Ball. He then forms six normal 

 places from the same series of observations and from these determines 

 Elements C. These elements represent the normal places within 

 2".8 and +3".2. An ephemeris for 1874 is given in the same 

 reference, page 374. 



Preliminary Elements D, based on observations 1872, November 25, 

 December 4, and December 12, are published by H. Richter. 6 



Elements E, based on eight normal places from the first two oppo- 

 sitions (1872-1874) were computed by Ball. 6 The normal places are 

 represented in the plane between +2". 13 and 2".54 and perpen- 

 dicular to the plane between +2".7 and 2".3. The special per- 

 turbations of Jupiter and Saturn were taken into consideration. 



Further Elements F for a new epoch and mean equinox, in which 

 the special perturbations due to Jupiter and Saturn have been taken 

 into account, have been published by Ball 8 and also an ephemeris 

 for 1875. 



The maximum correction to the ephemeris 7 computed from Ball's 

 elements, for July 1880, is Aa +2 3 .14 and AS +12".0. 



Elements G by Palisa are published and used in B. J. 1883, to B. J. 

 1893. They are based on 5 oppositions 1872-79 and include the 

 perturbations by Jupiter and Saturn. 



Ball's elements are again published and used in B. J. 1894 (see 

 Elements H) to B. J. 1913. 



Empirical corrections 8 were applied to Ball's Elements H, 9 by 

 Berberich. 



The most extensive investigation on this planet is by Leuschner. 10 

 The Elements I are based on observations extending from 1872 to 1899 

 and include the general perturbations due to Jupiter of the first order. 

 These elements and perturbations are used in the B. J. 1915 and to 

 date. 



The correction to the ephemeris 11 based on Elements I on June 16, 

 1921, was Aa +0 m .6 and AS 1'. Corrections to these elements 

 should be applied only on the basis of higher order perturbations by 

 Jupiter and of perturbations by other planets. 



