Hi Carlton,
Thanks for the response, it's made a few things clear.
My camera ffd (flange to film distance) is 44mm for a 450d
My T adapter is 13mm.
And my coma corrector is 44mm to the first element with the connecting tube (which I find out is for visual only)
So total that's 105 from sensor to corrector.
No wonder it's out of focus!!
After a bit of a search I found these.
https://www.bintel.com.au/product/bi...v=6cc98ba2045f
And this
https://www.bintel.com.au/product/t-...v=6cc98ba2045f
At the moment my camera adapter hasn't a thread so I need a new adapter with a 42mm thread, then a T48-42 adapter and hopefully these together will be 36mm. Then with my distance to sensor at 44mm it will make up the difference.
Knowing my luck it will still be about 10mm short !!.
I'll wait and see what comes in the mail.
Maybe I need a spacer??
It's a bit hard being about 350km to the closest telescope shop but that's why I've got zero light pollution.
Cheers
Andy