A digital TV detector system for the measurement of accurate radial velocities of stars of intermediate to late spectral types is described. The radial velocities are derived by cross correlating the spectrum of the unknown star with that of a radial velocity standard of similar spectral type. The radial velocities of 11 stars in the globular cluster NGC 6397 have been measured to a mean accuracy of 1.5 km/sec. The velocity dispersion is 3.1 plus or minus 0.7 km/sec and the ratio of central mass to blue luminosity is 1.3 plus or minus 0.6 in solar units.
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Costa et al. (1977) studied this question.