Narrow-band photometry of comet Austin 1990 V

Photometric observations of comet Austin 1990 V carried out at the Skalnaté Pleso Observatory on three nights of May 1990 are analysed and discussed. The comet was observed in the post-perihelion phase about two months after perihelion at heliocentric and geocentric distances of 1.201 and 0.244 AU, respectively. Emission band fluxes Fe and continuum fluxes Fc are presented, from which the total numbers of molecules M in the columns encircled by the diaphragms (39,000, 24,300, 14,400 and 8700 km in our treatment), are calculated. The production rates Qν are estimated from the conventional Haser model. Comparing with published results it is found that the production rate of C2 parent molecules after perihelion varies as r−2.1 and of CN as r−3.4. The results are in agreement with a suggestion that different formation mechanisms for the two radicals are present.