A description is given of a rapid method of using a spectrometer to give reproducible photoelectric measures of integrated intensities over significant features of stellar spectra, without the necessity for a sky of photometric quality. The accuracy achieved is 1 per cent. The λ 4200A CN band has been measured in 712 late-type stars and the G band in 212 of these. Absolute magnitudes derived from CN intensities have mean errors of at least 1 m. 5. There is only a weak correlation of weak CN with high space velocity. “Weak-line” stars have no anomaly in their CN absorption; “strong-line” stars have slightly enhanced CN. For G to K1 stars the spectral type deduced from G band intensities has a mean deviation of 0.15 class from the MK type. There is a small absolute magnitude effect, the G band strengthening with intrinsic luminosity. High-velocity stars have completely normal G band intensities. “Weak-line” stars show the G band very slightly stronger, “strong-line” stars show it slightly weaker than the mean, but the individual scatter is fairly large and the difference between the two groups is scarcely significant statistically.
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Griffin et al. (1960) studied this question.