astrophysics - What more could be learned from a rare astronomical event if we knew precisely when it would occur?

This is actually related to a question I recently asked on Worldbuilding, but seemed more appropriately asked here.

To keep this from being too broad in scope, let's assume that someone figured out the exact moment that Eta Carinae will go supernova (I wouldn't hold it against anyone if they suggested a more scientifically interesting event).

Due to this foreknowledge, we could point every telescope we have in its direction for the main event. Is there any science we know we could do/learn from this event that we wouldn't get by reacting to it after the fact? I know such an event would generate data for a century or more to come, but I'm interest in the moment of the explosion.

Somewhat related, is there anything we would/could do now to prepare for it if this event were going to happen today?