PHOTOMETRIC-STUDY OF COMETS P FAYE 1991-XXI AND ZANOTTA-BREWINGTON 1992-III/

We observed comets P/Faye 1998 XXI and Zanotta-Brewington 1992 III fro m the ESO La Silla Observatory (Chile) photoelectric photometry and CC D techniques. We used narrow-band filters to calculate the Afp paramet er and gas production rates for both comet. P/Faye has a low Q(CN)/Af rho of 14 x 10(21) molec s(-1) cm(-1) at perihelion, but a typical red dening between 11 and 15 %/1000 Angstrom (between 4845 and 6840 Angstr om). Furthermore, CCD imaging revealed a faint and diffuse asymmetry a ttributed to anisotropic outgassing. As expected for a newly injected comet, Zanotta-Brewington has a high Q(CN)/Af rho of more than 110 x 1 0(21) molec s(-1) cm(-1), which decreased with CN activity in March 19 92. No reddening is measured from the continuum filters.