VRI imaging of comet 46P/Wirtanen

Imaging of comet 46P/Wirtanen was performed in the standard VRI filters on 10 and 11 November 1996 with the 1.0 m telescope of the South African Astro nomical Observatory (SAAO). After proper processing and calibration, the im ages have been used to derive information about the isophote distribution, magnitude and colour indices. We observed a coma extending to at most simil ar to 5 x 10(3) km. We derive absolute magnitudes of the coma for the diffe rent filters and the colours V-R = 0.18 +/- 0.17 and R-I = 0.39 +/- 0.16. T he Af rho value (related to the dust production rate) for the R filter-is 1 0.5 +/- 0.6 cm. The radial profile (azimuthally averaged) of the surface br ightness in the R filter has a slope of -0.9, which is consistent with a st eady-state dust production. The results are compared with other observation s in different periods. (C) 1999 Elsevier Science Ltd. All rights reserved.