targetting destroyers

[drazic]

i know it's almost idiotic to do but i was trying to lure them away from the convoy,deal with the destroyers first and then get back at attacking the convoy submerged .
while i was getting the destroyers attention and at the same time i get a clear shot with a torp i can take it without worrying about the deck gun .
so if i understand correctly i "aim" with the binoculars ?
grtz