When we slewed back to the occultation target after 2 am, a VERY bright "star" had entered the FOV. This must be the asteroid itself, and I started to capture at 1 frame/5 minutes to record the movement of teh asteroid.
As it approached 04:59, the start of the "bracketed time", the star and the asteroid were very close but definitely separated. Exposure was cut to 1/15 second and still the 12.1 mag star was clearly visible. Video recording started and the screen visually monitored until the 2 separated again at 05:15 am, the end of the "bracketed time".