I have now approximately subtracted the emission component from the spectrum of the central 6 arcsec and divided it by the solar spectrum to produce a reflectance spectrum.
It looks similar to some asteroid reflectance spectra. Since the central region is so condensed and from images there does not appear to be much dust is it possibly representative of the comet nucleus albedo or is it just scattering from dust of a particular particle size distribution? Does anyone have a feel for how bright the nucleus would appear in reflected sunlight at this distance if not active?
Robin