Do a bit of visual imagination...
Two absolute items that you know
- your course
- Scope bearing of the target.
and approximate..
- AOB of the target
With practise you can determine the Angle On Bow (AOB) of the target.
IOW, the bearing that the target would see you.
A simple thought experiment.
- you're traveling North (000 degrees)
- the target is at a bearing of 315 (45 degrees port/left)
- The AOB is 45 degrees (starboard/right)
You target course is your course + (Bearing + AOB) = 000 + 045 + 045 = 90 (East).
With a bit of practise in 'compass' mental gymnastics is becomes as easy as pie.