Sct with binoviewer does not operate at f/10, but somewhere between f/12-13. Your setup with 19 panoptic & 2x barlow should be operating at about 200x magnification, which should be within the capability of your C6. The Denk II can give sharp images up to at least 390x, so that should usually not be the issue. Unless the seeing condition is bad that night, it should not be difficult to get sharp images of Jupiter or the Moon at 200x magnification.
Before we can assess further, it will help if TS can answer the following:
Did you check your sct collimation before you observe?
Did you check your diagonal alignment, with and without the binoviewer?
Did you collimate your sct together with the binoviewer?
Did you check the seeing condition/limit that night, with some eyepieces/barlow but without binoviewer?