358 



12 



Nr. 63, p. 16, Tab. 8 and 9) may be compared. The mean errors here found are 

 somewhat greater than those derived in case of the cluster NGC 1647 (Ap. J. 42, 92; 

 1915). Part of this difference will at any rate be due to the fact that the plates of 



Table 5. 



Precision of effective wavelengths, spectra of P' order. 



diameter of central image, d -05 -06 -07 -08 -09 -10 -11 mm 



mimber ot differences used 82 125 222 254 246 211 165 



square of mean error oî I 843 428 281 138 89 ■ 57 61 ß^ 



weight of 7;^ 3-0 5-9 9-0 18-3 28-4 45 41 m-2 



mean error of 7;, ±-58 ±-41 ±'33 ±-23 ±'19 ±'15 ±-16 m 



diameter of central image, d -12 -13 •14,-15 -16, -17 -IS.-ig -20, -21, -22 mm 



number of differences used 177 66 80 121 70 27 



square of mean error oî I 44 40 54 64 39 33 ,«2 



weight of /x 57 63 47 39 66 77 m^^ 



mean error of /; ±-13 ±-13 ±-15 ±-W ±-12 ±"11 m 



Table 6. 



Adopted weights, spectra of P' order. 



diameter of central image, d -05 -06 -07 -08 -09 -10 -11 -12 -13 •14 mm 



adopted normal weight of /; 2 4 8 18 28 38 48 56 58 52 m-2 



diameter of central image, cf -15 -16 -17 -18 -19 -20 -21 -22 23 ■24 mm 



adopted normal weight of /;, 44 36 28 22 16 12 18 6 4 2 m-2 



NGC 1647 were measured three times. The marked decrease in accuracy for the 

 fainter images, formerly (Potsdam Publ. 1. c.) found, is also shown by the present 

 measures. 



6. Determination of Approximate Magnitudes. 



The estimates of the diameter d of the central star image were converted into 

 provisional magnitudes according to Table 7, adding the constant of efficiency 









Table 



7. 















diameter of central image, d . . . . 



•04 



•05 



■06 



•07 



•08 



■09 



•10 



•11 



•12 



•13 



•14 ^15 



provisional magnitude equivalent m' 



7-0 



6^5 



6-1 



5^6 



5^2 



4^8 



4-5 



4-1 



3-8 



3-5 



3^2 2-9 



d 



•16 



•17 



•18 



•19 



•20 



■21 



■22 



•23 



•24 



•25 



■26 ^27 



m' 



2-6 



2-3 



2^1 



1-8 



1-5 



1-2 



1-0 



•7 



•5 



•3 



■1 --2 







d 



•28 



•29 



•30 



•31 



■32 



■33 



■34 



•35 



•36 



•37 



■38 -39 



m' 



—•4 



-•6 



-•8 



-1^0 



-1^2 



-1^4 



-1-6 



-1^9 



-2^1 



-2^3 



-2-5 -2^7 







d 



•40 



•41 



■42 



■43 



■44 



■45 



•46 



■47 



•48 



■49 



■50 mm, 



m' 



-2-9 - 



-8-2 - 



-3-4 



-3^6 



-3^8 



-4^0 



-4-2 



_4-4 



-4^6 



-4^8 



-5^0 



given in Table 1 for each separate plate. The mean provisional magnitudes thus 

 obtained for each star were finally reduced to the scale of A. N. 4767 by means of 

 a table made according to the formula 



