ok seeing as though i have only just found out what AOB means, i think i may be able to help with the most useful trick you will probably learn about the subject, as i haven't seen it in the forums yet.
Ok so if AOB is the enemy captin's bearing of you all you have to do is simply take a back bearing.
Now i havent done this in a long time and being in the british army, instead of DEG we use MILS. but the math is the same. so stick with me here.
If the bearing of the enemy ship is from 0-180 DEGS (starboard) then take the bearing your watch officer gives you or the bearing you take manually on the map and ADD 180 deg to the bearing.... this will give you your back bearing.
If the bearing of the enemy ship is 180-360 DEG (Port) then the opposite is applied and 180 deg is subtracted from the bearing of the enemy ship from you.
Now like i said i havnt used this for months, and it was in mils not deg. but hey the maths is all the same
Good hunting folks and i hope this helps