Hi all, remote setup is STX16803 / FW7 / STX-Guider / AOX (beyond the AOX is a field flattening optic, sealing the front end) We had an accumulation of dust at a distance of ~ 3/4" from the sensor (measured using the dust donuts on the flats). We pulled the camera, opened, blown the window and filters and put back together. Within weeks, the flats/images are covered in dust again and measured at the same distance (around 0.75 - 0.76 inches from the sensor. The imaging system should be sealed once all attached. I've included a couple of flats (different filters). Adjusted the images to highlight all the dust. where can dust be getting into the system? thoughts? It's difficult to assess without being on site to deal with this. The techs onsite have put it together twice now, and don't see any gaps. thanks, ..paul M.