One thing I never quite understood...
The doomsday machine could blow a planet up with one shot... the Constellation and Enterprise absorbed multiple shots from this ship...
Does that mean the Constitution ship could absorb more damage than a planet?
Well planets don't have shields, and we get the impression it took it a while to cut a planet up into bite-sized chunks... it's not a one-shot deal like the Death Star vs Alderaan. And I always assumed it tuned the attack to the target.