[alocky (Andrew lockwood)]

Hi all,
I just picked up a secondhand 14-24mm lens, having hired one previously and been suitably impressed. This weekend I plan to give it a workout.
When I've tried time lapse movies with the D800 through sunset, I noticed the automatic iso occasionally jumps too far and the resulting movie has a flickering background. Can anyone share their tricks for reducing this?
Cheers,
Andrew.