Here's a blast from the past about an aiming system using clock position for aim points on the ball edges. His clock is a bit small so I made a mirror clock to use instead. The advantage is you only need one time for both OB and CB.
https://forums.azbilliards.com/showthread.php?t=111725&highlight=clock
https://forums.azbilliards.com/showthread.php?t=111725&highlight=clock