C2, H2O(+), and dust distribution in Comet P/Halley near opposition

Comet P/Halley has been observed using a CCD camera equipped with four interference filters selected from a set distributed by the International Halley Watch (IHW) Photometry and Polarimetry team. The observations were done from 1985 October 21 to November 11 at ESO. These, combined with exposures of a standard star, make it possible to follow the evolution in extension and brightness of the gas and dust components of the inner coma. The observations made on November 11.3 when the comet was seen almost "head on", can be fitted very nearly to an apparently uniform expanding coma model, from which the scale lengths of C₂ and H₂O⁺, and their parent species are determined. The surface-brightness distributions and the radial profiles are given.