[PLASKETT] THE SPECTROSCOPIC BINARY fi ORIONIS 225 



When these are applied to the preliminary values we obtain. 

 ELEMENTS OF /? ORIONIS 



Name 



Eccentricity 



Half- Amplitude 



Longitude of Apse 



Periastron Pasvsage .... 



Period 



Velocity of System .... 

 Projection of Semi-axis 



Maximum Velocity 



Minimum Velocity 



Symbol Preliminary 



Corrected 



0.20 



0.29G±.059 



It will be noticed that, except for the eccentricity, the changes in 

 the elements are very small and a comparison between the residuals 

 from the corrected ephemeris and from substitution in the observation 

 equations shows that tliie solution is satisfactory enough as there are no 

 differences greater than .25 km. It was not deemed necessary to make a 

 second solution considering the assumptions made in combining the 

 observations. That the solution has improved the elements was shown 

 at once on comparing the curws and is also evident by the reduction of 

 2puu from 3.88 to 3.16. 



The probable error of a normal place of unit weight is ± 0.40 km. 

 The probable error of a night obtained by scaling from the curve is 

 d= 1.80 km. The probable error of a plate obtained with a dispersion 

 of three piisms ± 1.98 km., with dispersion of one prism ± 3.22 km. 

 and including all the plates it 2.62 km. If, as was done, the observa- 

 tions are divided into two sets those before and those after January 29, 

 1909, when the sudden change in amplitude was /noticed, and separate 

 curves and elements are obtained roughly for these sets the probable 

 error of a night reduces to ± 1.37 km. with a proportionate reduction 

 in the probable errors of single plates, and this would probably be not 

 much greater than 1 km. if the amplitude remained constant. For the 

 two sets mentioned above it may be of interest to compare the maximum 



