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Horst U. Keller, Kai Rembor (Max-Planck-Institut fuer Aeronomie, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany)
A new approach to obtain the size distribution function of cometary dust grains and their production rate as a function of time from wide-field (CCD) observations of a comet after perihelion is described. As a simplification it is assumed that the dust size distribution is time independent and that the effects of dust emission anisotropy and velocity are negligible at the resolution of the observation. The analysis consists mainly of a transformation of the images from spatial coordinates to 'dynamical' coordinates t (emission time) and (radiation pressure to gravity ratio). The size distribution function and dust production rate are then extracted along lines of constant and lines of constant t respectively, exploiting the fact that the observed surface brightness is proportional to the size distribution function and the dust production rate. The method is exemplified by the analysis of observations of comet C/1996 B2 (Hyakutake) with the C3-camera of the LASCO coronagraph on board the SOHO spacecraft. Results for the dust production and dust size distribution of comet C/1996 B2 (Hyakutake) are presented and discussed.