If you don't use a filter wheel or filter holder, you can use a 20mm adapter or extender between the OAG and the camera to achieve the correct back focus for both the guiding and main cameras.
You won't need this adapter if you use a filter wheel or a filter holder.
The preferred method for connecting this adapter is by using the provided screws to bolt it to the front of the camera. Then, bolt the OAG to the adapter.
For cameras that do not have the six threaded holes in the front, this adapter features an M54(f) thread on the camera's side and an M48(f) thread on the OAG's side.
