Stellar clusters 



51 



TABLE 11 giving the mean spectral-index corresponding to a given 



color-index. 



Color- 



Spectral 



index 



type 



" 0.4 



— 0.70 



B-i 



— 0.2 



— 0.30 



Bl 



0.0 



+ 0.10 



.11 



+ 0.2 



+ 0.50 



.15 



+ 0.4 



+ 0.90 



.19 



+ 0.6 



+ 1.30 



F3 



+ 0.8 



+ 1.70 



Fl 



Color- 



Spectral 



index 



type 



+ 1.0 

 + 1.2 



+ 1.4 

 + 1.6 

 + 1.8 

 + 2.0 



+ 2.10 



+ 2.50 

 + 2.90 

 + 3 30 

 + 3.70 

 + 4.10 



G i 

 Gb 

 Gd 

 K3 

 Kl 

 Ml 



In fig. 4 the value.s of the color-index from table 10 are compared with the 

 observed color-indices from Yerkes, Harvard and Göttingen. The agreement can 

 be considered as satisfactory excepting perhaps the color-indices of the 5-stars 

 which are throughout somewhat smaller than the table values depending possibly 

 on accidental errors which are not sufficiently eliminated by a so small number of 

 observations. In like manner the spectral-indices corresponding to negative values 

 of the color-indices must be considered as rather uncertainly determined. 



