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Published online by Cambridge University Press: 14 August 2015
Photometry of the K line of calcium in A-type stars is useful in segregation of Am stars and in estimating the metal abundance of field stars and of stars in clusters. To date, K-line photometry data for six clusters have been analyzed using uvbyß data: Hyades, Pleiades, IC 2391, and IC 2602 (Hesser and Henry 1971), Orion (Hesser, McClintock, and Henry 1977), and Praesepe (Henry, Anderson, and Hesser 1977). We present similar analyses for the Coma and NGC 6475 star clusters, using the uvbyß data of Crawford and Barnes (1969) and of Snowden (1976) respectively. The Coma stars closely resemble field stars. NGC 6475, on the other hand, is most remarkable. Of 31 stars for which complete data are available, 9 are metal-rich, 3 are metal-poor, and 19 (about 2/3 of the stars!) are Am.