Optical spectroscopy of comet C/1995 01 Hale-Bopp

We report the results of optical CCD spectroscopy of comet C/1995 O1 Hale-Bopp on 1995 August 30, when the comet was at a heliocentric distance of R(h) = 6.82 au. In the wavelength range 3300 to 5500 Angstrom the dust coma is found to be red compared with solar colours. Near the nucleus and in the prominent jet observed at this time the dust is redder than in the surrounding coma, implying differences between the grain populations in these regions. Emission from the CN (0-0) band was detected at a level of (1.7 +/- 0.8) x 10(-14) erg s(-1) cm(-2). This is the first reported optical detection of gas molecules in the coma. Monte Carlo modelling gives an outgassing rate of Q(CN) = (6 +/- 3) x 10(25) molecule s(-1) at this time. From a comparison of these and other reported observations, Hale-Bopp appears to be a normal comet, albeit highly active.