The 15 years of comet photometry: A comparative analysis of 80 comets

In 1976, a program of narrowband photometry of comets was initiated that has encompassed well over 400 nights of observations. To date, the program has provided detailed information on 80 comets, 11 of which were observed during multiple apparitions. The filters (initially isolating CN, C2, and continuum and later including C3, OH, and NH) as well as the detectors used for the observations were changed over time, and the parameters adopted in the reduction and modeling of the data have likewise evolved. Accordingly, we have re-reduced the entire database and have derived production rates using current values for scalelengths and fluorescence efficiencies. Having completed this task, the results for different comets can now be meaningfully compared. The general characteristics that are discussed include ranges in composition (molecular production rate ratios) and dustiness (gas production compared with Af(rho)). Additionally an analysis of trends on how the production rates vary with heliocentric distance and on pre- and post-perihelion asymmetries in the production rates of individual comets. Possible taxonomic groupings are also described.