Used my 600mm with both the 1.4x and 2.0x extenders stacked.
The EXIF data says 1200mm, but it is wrong. It was really 1680mm.
Guess the camera just read one of the extenders being present.
Shot from my tripod with no motion platform.
Shooting out an upstairs window in a suburban neighborhood with lots of light pollution.
But you can tell it is Saturn.