Abundance correlations among comets

Results of narrowband filter photometry are presented for comets 1977g, 1978b, 1978f, 1978j, 1979c, and 1979i. There appears to be a remarkable homogeneity among comets with regard to the relative production rates for those species which are readily measured, specifically C2, CN, C3, and OH. Most comets appear to show identical relative abundances, except for a rather well-defined variation with heliocentric distance. Molecular production rates appear to be unrelated to either the emission-to-continuum (gas-to-dust) ratio or the dynamical age of the comet. The correlation with visual magnitudes is excellent, though the slope is not what could be intuitively expected.