Essentially, you need to trap the dust as close to its source as possible....once it gets airborne and away from the lathe, then you'd need an almighty extractor fan and a similar open vent somewhere, to provide sufficient airflow. To be honest, I doubt that this is an issue that you will be able to fully control, but rather, you will be able to minimise it. Try setting up a series of rails and hanging shower curtains around the lathe (at a safe distance to avoid them touching or getting sucked in to any moving parts) and set up a dust extractor with a hose and terminal that can be adjusted - sometimes referred to as 'posable' - to extract as much dust as possible right at the source. A further help would be a good sized air filter suspended above and reasonable close to the lathe.