Standard stars for cometary photometry

Five narrowband interference filters centered at wavelengths 0.365, 0.387, 0.406, 0.484, and 0.514 μm have been selected by the International Astronomical Union to represent ultraviolet continuum, CN emission, C₃ emission, blue continuum, and C₂ emission in the spectra of comets, respectively. We present adopted magnitudes and colors in this filter system for 50 standard stars ranging in blue magnitude 4 to 12, in spectral type from O to K, and mostly distributed around equatorial regions of the sky. Tabulated uncertainties are generally on the order of 0.02 mag or smaller. The zero points of the photometric system are chosen such that blue-continuum magnitudes are approximately equivalent to Johnson B, and such that color indices average zero for solar analog stars.