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Hey robin,
This is what im seeing. yes the stars are on the pi55 but and they are consistent problem is that its not consistent with coma. why do i say this. well coma is radial from the center out your either under or over corrected your stars arn't radial they are a bit all over the show. I think if you really wanted to get good results you would have to move to the keller corrector not the reducer but the corrector version.
I could well be completely wrong but with the secondary i thought that its alignment was to do with illumination more than anything. As there are 4 different types of alignments of which if you can nail down 2 out of 4 your system is perfectly collimated. there is a really good read about it on the cloudy nights forum.
I still think something is pinched or warped as even though im nearly 1 f number slower than you my secondary isn't quite aligned and i don't have these issues.
As for centering the secondary properly a proper sight tube does it for you something like the cats eye sight tube.
Keep us in the loop of what happens because ide like to know whats the cause behind this annoyance
Brendan
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