I use the Orion Field flattener for short refractors - this both adds the extra length required to reach focus and gives a much better field. It has a thread on the camera end which screws straight into the t-mount adapter. I seem to remember a 50mm extension tube and 2 - 1 1'4" adapter was too long to reach focus with the camera. It's a nice little scope but there's certainly a bit of color if you push it - it's not as good as the ED80 (at least my example isn't).
Skip to the 3 min mark and I'm talking about focussing a DSLR....
https://youtu.be/TfZmL0XfTJk