There is no general rule. It depends on the position of the eyepiece's entrance pupil when the eyepiece is inserted all the way into the focuser tube or the Barlow lens tube as the case may be. The entrance pupil is a ring in the tube just forward of the front lens of the eyepiece, and it forms the sharp edge of the field of view.

So far it is not clear as to what lenses are in the optical path between the camera body and the diagonal as shown in your second picture. I am guessing that the Barlow lens is in its normal position. Have you placed another lens, such as one of the eyepieces, inside the adapter between the Barlow and the camera? If so, is it accurately centered and aligned with the optical axis?