I have a SkyWatcher 80ED and an ASI294 MC. I want to use a 2X or 3X barlow with this rig. My back focus distance is 66mm. When I use my DSLR or 294 set at this BF, everything works fine. If I introduce a barlow to the train, does the 294 sensor still have to be at the BF or is it the barlow lens...or is there another requirement?
