Home from travels now and I've had a chance to re-visit some of my spectra taken from White Cliffs, NSW. This one is of C/2012 S1 (ISON), taken after it had a massive increase in brightness on around 13 Nov.
The broad diatomic carbon emissions are the principal features - unfortunately the main CN line is outside the range of my camera. The spectrum clearly shows that dust was not a significant contributor to the brightness of the comet at that stage. If it was, the C2 peaks would appear to emerge from a broad hump of sunlight continuum reflectance - of that there is no sign.
VSpec created spurious double peaks on the comet and on the brightest emission line, probably a saturation issue or something. I patched them with dotted lines, and faded the dipping lines.
Cheers -