Maraz is correct. I just double checked it. If the scope lock on the target is broken... you are then unable to use the data notepad to automatically calculate the range once you identify the ship type/mast height. The range calculator does indeed work with no officer assistance.
At longer ranges the lock is broken more easily. So you gotta get
closer to the target
.
For the most part (spoiler here) if the target lock is breaking quite readily... It's probably a hail Mary shot with your torps there. I could get more specific... but I don't want to ruin the human-error element for you. If you hit everything all the time you'll get bored.
Sorry for the delay on getting you the answer. I don't get to sail much... my manual targetting was/is rusty. (LOL, running a function test to check your problem query, I missed a medium cargo at 2000 meters because I forgot to factor in the speed of the target.
)