Thanks for all your replies. However, I said that the photos have the person in the SAME place and the centre of the photo is a bit blurred.
If you stop the turret, you will get a bright over-exposed bar in the middle. If you run around to catch up to the lens, you will be in a different place.
The shutter speed on the HorizonT does not change the speed of the rotation, just the size of the slit. Slowest shutter speed is 1/30. The newer Horizon has a two speed turret but the slowest speed is still pretty fast.
Maybe I'll contact Jeff and/or try moving the camera as I suspect he does.