Almost certainly you won't bring your DSLR to prime focus (ie just using the bare camera body on the focuser, no eyepiece) with your newt as it is, without modification..... Newtonians generally have insufficient back-focus - so you need to get the camera's sensor closer to the mirrors, but the focuser won't rack in far enough....
So you need a low-profile focuser, or you need to move your primary mirror up the tube.... like I did in 2006....
My thread
here.... as you can see there are other ways to do it, I found giving it the chop fairly easy and painless, I just use an extension tube to compensate when using eyepieces now, and it works fine.