CN STRENGTHS IN M67 AND NGC 188

Using (R-I), (B-V) and Spinrad and Taylor's T -index as temperature criteria, it turns out that the CN blocking fractions measured by them in M67 and NGC 188 giants are consistent with metal abundances intermediate between those of the Sun and the Hyades except in the case of stars in the 'clump' at (B-V) 0 1.05, Mv 1.0. © 1974 Royal Astronomical Society. Provided by the NASA Astrophysics Data System.