Is this how you get target AOB?
 

Coming back to SH3, I decided to try manual torpedo aiming and I am having trouble with calculating target AOB. Is this how I do it on nav map?
https://www.subsim.com/radioroom/[im...om/wKc8hFl.jpg
https://i.imgur.com/wKc8hFl.jpg
https://imgur.com/wKc8hFl
Basically I would put my submarine on 90 degrees or so and then I would mark straight line where my heading is and then I would do the same for target enemy ship and I would get intersections of two lines where I would put protractor in the middle and get AOB by looking enemy heading line through protractor... Am I doing it right or wrong?

There is a drawing tool for the map (protractor) where you click on your uboat, it starts a line stuck to your cursor. Then click on the target position, this fixes the first line. Then move the cursor to on the target course and click. This creates an angle between the two lines in the corner. This would be the angle on the bow for that target position. But that sounds like what you are writing.

IMO, the best way to think of AOB is to imagine you are on the target ship. Which ever direction you need to look at your submarine is the angle on the bow.