help with newt optics etc

[graham.hobart]

Hi folks, I got myself a cheap Bintel 8' f5 recently (well ordered in May, arrived last week). I also bought the GSO 2" coma corrector.
I tried to collimate with a laser, then took this picture canon 1000d with 20mm of spacer plus M48/M42 step down ring (thin)on the coma corrector.
Now i have read various threads regarding spacing for this CC- either 75mm or 80mm or 55mm!
My question
does this pic represent
?poor collimation?
bad coma corrector spacing?
Pinched optics?
a mix of all the above?
I was guiding with a zwo mini guide scope at 0.20-0.30 RMS so hope it wasn't polar alignment, and it seemed balanced ok on the PMX.
Help please before I buy more astro bits and bobs!!
Graz

[graham.hobart]

NB this was a 300 sec frame at iso 800 I think un touched except for changing it from a raw to jpeg for the space (not stretched).

[multiweb]

Definitely a bit of pinched optics. Maybe a little tilt. How was your guiding?

[graham.hobart]

I thought guiding was ok with a zwo mini guide camera and flattish line in PHD 2

I will back off the primary mirror screws a bit

[multiweb]

It's tilt then. But start with the primary until you've got round star then you can post a new shot. Try no to blackclip it. Easier to see star shapes when they're blown out with a lighter background.