That's almost right. It shows a box between the condenser and ground. If that's the ballast, it's in the wrong place. It's also my understanding that the common point is usually the + connection and not the points connection. This can be verified with an ohm meter.

When those points open, the ringing occurs between the primary and condenser (as in any LC circuit). That causes an alternating magnetic field in the core, thus the AC at the plug wire.