CELESTIAL MECHANICS: LEUSCHNER 61 



represents the normal places, AaCOsS between 7".l and +3".8, and 

 AS between 1".6 and +3".0. 



With Elements D and special perturbations, the maximum residuals 

 for opposition of 1912 were Aacos8 = +2M2 and A8 = +26".6. 

 Stromgren, assisted by Julie M. Vinter Hansen, 7 again investigated the 

 orbit of Hektor on the basis of thirteen normal places (1907 to 1912). 

 A least square solution led to Elements E. At the conclusion of this 

 work, 7 osculating elements were computed for the epoch of each year, 

 1907 to 1913, based on Elements E and the special perturbations pub- 

 lished in the same reference. The ephemeris for 1913 was published 

 in A. N., vol. 198, p. 367. 



In A. N., vol. 200, pp. 79-82, Stromgren publishes the comparisons 

 between the observations and the ephemeris, which was based on 

 Elements E and the perturbations due to Jupiter and Saturn, for 1913 

 and 1914. The maximum residual for 1913 for Aacos8=+0 8 .53 and for 

 A8=+7".l. For 1914 the maximum residual for AacosS=+0 3 .51 

 and AS=+H"-6- Stromgren regards these residuals as satisfactory. 



As an application of Leuschner's satellite method, S. Einarsson 3 

 computed a preliminary orbit of Hector based on observations 1907, 

 February 10, March 11, and April 16, Elements F. These elements 

 represented an observation of May 2, 1908, as follows: Aacos8 = 

 4' 32".4 A8=+3' 31".9. With Elements F, the special perturba- 

 tions by Encke's method were computed for the 1907 opposition. New 

 elements were then computed from observations 1907, February 10, 

 March 11, and a normal place from observations April 12, 16, and 19, 

 by a differential correction of Elements F. These new Elements G 

 represented the opposition of 1908, May 2, as follows: Aa + 30", AS -^. 

 95", and for 1909, April 17, Aa + 6M; AS 6'.7. The application of 

 Leuschner's method thus yielded far better results than the ordinary 

 method followed by Stromgren: 1908, Aa= 9' 15" AS=+6' 18". 

 No further work was done on this planet by Einarsson since Strom- 

 gren and his colleagues had already made extensive investigations. 



An ephemeris for 1915 is published by J. Fischer-Petersen, 9 using AN. 

 Elements E and taking into account perturbations due to Jupiter and 

 Saturn. 



The elements and ephemeris for 1916 10 are based on Stromgren's KPJ; 

 Elements E with special perturbations by Jupiter and Saturn brought 

 forward. 



Elements and ephemerides are given in Kleine Planeten for each 

 year to 1921. No further comment is published regarding the elements. 



An ephemeris is published by M. Henri Blondel 11 for the opposition M 

 of 1921 which has been corrected on the basis of an observation at 



