Thanks guys, when I do a widefield I like to get a number of objects in the fov to give it some dimension. NGC5128 is quite faint but more data would have helped that although that is the first time I have gone after that target and didn't know how it would compare alongside Omega Centauri.
I knew the alignment wasn't right when I tried with the 300mm lens so I stayed with 100mm but I have added the crops of both objects so you can see whats possible with a camera lens.
Omega centauri crop
http://lh3.ggpht.com/_2r9eqlTPDhc/Sf...ega%20cent.jpg
Centaurus A crop
http://lh6.ggpht.com/_2r9eqlTPDhc/Sf...0/Cent%20A.jpg