Abstract
Evidence that spectral differences observed among globular cluster giant stars with similar V and B-V values persist to fainter absolute magnitudes has been slowly accumulating in the past few years. In the case of 47 Tucanae, photometric evidence for CN strength variations extending to MV=1.5 mag was found from DDO photometry (Hesser, Hartwick and McClure 1976, 1977). Subsequently, CN strength variations at MV=+3.5, i.e., stars at the base of the vertical rise on the subgiant branch, were found by low dispersion spectroscopy (Hesser 1978). Kraft (1979) and collaborators have found evidence for star-to-star variations in NH and CH strengths among subgiant stars below the horizontal-branch level in the metal-poor cluster, M92; and Hesser and Harris (1979) have found CN and CH features to exhibit wide ranges among similar stars in M22, a metal-poor cluster with some apparent similarities to the otherwise uniquely anomalous cluster, Omega Centauri.
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