1115 



Messier 3. 



.V. Cr. C. 5272; «,,„, = 13^' 37'" 35^ , .^„„ = + 28° 52',9, 

 b=: -\- 77°, /r=8°; class: 6' 3^). 



H. VON Zeipel, Catalogue de 157 J étoiles contennes dans I'amas 

 globulaire Messier 3 (N. G. C. 5272), Aiiiiales de I'Observ. de Paris. 

 Vol. XXV, J 906. 



The three photos used have been taken at Paris with the instru- 

 ment of the Carte du Oiel and the scale of magnitudes has been 

 determined bv the method generally used at Paris for the Carte du 

 Ciei, viz. by comparing the diameters of images exposed during 

 different periods of time. The zero point was determined in accord- 

 ance with the Harvard Photometric Revision. 



S. I. Bailey. Variable Stars in the Cluster Messier 3. Annals 

 Harvard Observ. Vol. 78, Part 1, 1913. 



This treatise contains i. a. the magnitudes of 22 stars, used for 

 comparing, found b}^ the meridian-photometer and by comparison 

 with the North Polar Sequence. The 137 variable stars have been 

 measured on 90 plates. Of 110 the luminosity- curve and the period 

 were determined. 



Of the 22 standard magnitudes of Bailey 20 occur also in Von 

 Zeipel. With the aid of these stars we examine how far Von Zeipel's 

 scale of magnitudes is right ^). To this purpose we compare v. Z.'s 

 magnitudes with the photometric ones in Bailey, Table I, column 15. 

 It will be seen then that V. Z.'s magnitudes are, all of them, 1™.4 

 too bright. If we count the stars of Von Zeipel's catalogue and apply 

 a constant correction = -\- 1"\4 to the magnitudes we shall find the 

 following numbers: 



^^ ^ = 3.37. This makes - 0.42 = 10.9 + 5 + 5 log 7t 



110.9 



%jr = 0.74—4 jr=zO".0005* 



Also : -^^ = 3.44 makes :i — 0".0004 



^11.4 

 -^12.9 

 ^11.9 

 ^13.4 

 ^12.4 



= 3.09 ^ = 0".0005 



= 2.72 n = 0".0006 



^) The position and the distribution in classes has been taken from Annals 

 Harvard Observ. Vol. 60. N^. 8. 



•) The correction for the magnitudes of Bailey by Shapley (Proc. Nat. Acad. 

 Vol. Ill, p. 480) only refers to fainter stars than those employed by us. 



