[brajoh (John bradshaw)]

Thanks for the comments Mike.
There is drift and coma +/- astigmatism (chromatic aberration? - less severe colour in the flatter pictures) — I had the HEQ5 overloaded by weight so there was some drift, and the focal reducer certainly adds artefact (see bright star extreme right esp in the less contrasty pictures). There are also black dots in the centre of some stars — the more processing the more problems overall.

I have previously only used the C8+FR with ZWO178 (small chip small pixels) so three times the gain, 3 times the lack of sharpness (generally disappointing) cw the 4/3 chip. I tried collimating before these shots but couldnt improve it with the seeing that night (in fact didnt change it). So I was pretty surprised how much detail there was — but bigger chip, more problems in the periphery.

There's always that temptation to want other equipment and (mainly for the sake of less difference in focal point with from blue to Ha that reflecting surfaces) I was thinking about changing to a newt (but wonder how much colour problems come out of the coma corrector and would I be any better off). But got an NEQpro at Christmas so will see what I can gain with more stability and balance being less critical before I consider that.

I notice you people seem to prefer chucking out compromised shots over more exposure and weighted preprocessing. I might look at redoing it with only the round stars if there are enough in the series.

Anyway, thanks for the comments.

John B