[RoaldLarsen]

OLC and Pisces have made me think about this even more, and I now think there is an even better method to fire at an arbitrary angle from an arbitrary course, if you know target's course and speed:

0. Select tubes, torpedo depth, torpedo speed, and salvo spread, and open tube doors any time before step 9
1. Unlock periscope from target.
2. Rotate periscope to bearing 0 degrees (or 180 for stern tube shot).
3. Decouple periscope from TDC to allow manual input.
4. Enter target speed on TDC.
5. Set AOB on TDC as 180 minus the difference between your course and target's course. (or AOB = difference in course for stern tube shot)
6. Couple TDC to periscope.
7. Rotate scope to target
8. Lock scope on target
9. Get a range reading
10. Instantly unlock scope from target.
11. Instantly decouple periscope from TDC to allow manual input.
12. Instantly enter range on TDC
13. Instantly couple scope to TDC
14. Instantly rotate scope to desired aiming point.
15. Fire immediately

And to avoid having to take a range reading, if you can afford to wait for a 0 gyro angle shot:
0. Select tubes, torpedo depth, torpedo speed, and salvo spread, and open tube doors any time before step 9
1. Unlock periscope from target.
2. Rotate periscope to 0 degrees. (or 180 for stern tube shot).
3. Decouple periscope from TDC to allow manual input.
4. Enter target speed on TDC.
5. Set AOB on TDC as 180 minus the difference between your course and target's course. (or AOB = difference in course for stern tube shot)
6. Couple TDC to periscope.
7. Rotate scope to target
8. Lock scope on target
9. Fire when gyroangle reads 0.

To fire at an aiming point other than centre of target, adjust final steps as in my earlier post ITT.