each of the lines approximates distance to the contact on that
bearing.
most folks aim at the formast of a ship as often aiming at the
centre (where you lock too) leaves the torp a long way aft
on the target and will often miss. try to have your ship aimed
close to the torpedos direction of travel so it wont lose time
making the turn. fire from 1000 to 800 yds for best results
and use the Q button to open your selected torpedo tube
so that the cycle time to open the door wont take you
off the target.
[edit] it is good to lock the target after the tube is open
then hit the checkmark on the data pad at that point
unlock move the crosshair to the foremast and fire.
as for depth settings and magnetic detonations Ill let
someone else cover that while Im at work.
and welcome aboard matey.
MM