CN Photometry of Comet Levy 1990XX

The results of photoelectric photometry with the narrowband CN and C3 IHW interference filters are presented. The observations were carried out with a set of diaphragms of different radii. The dust component of the cometary spectrum was not observed. Thus the flux in the C3 filter was treated as the upper limit for the dust component in the UV part of the spectrum. The raw flux observed in the CN filter makes the upper limit and after subtraction of the C3 flux makes the lower limit for pure CN radical flux. These limits were converted into the CN production rates according to the classical Haser model and the differences between them are smaller than 20%. The dependence of the production rate on heliocentric distance in the range of 1.7-1.3 AU is presented.