line of aim

[pcb]

hi, a bit confused and hope someone can help. i have selected the contact point on the object ball (bob) ps the advice i need is base on angled shot . then once i have selected the spot i wish to strike on the object ball do we draw a line back through to the middle of the cue ball or do we draw this line back to the leading edge of the cue ball as this the part of the cue ball that is going to strike BOB . My question is if its the leading edge of the cue ball why have i seen we draw a line from Bob to the miiddle of the cue ball. please help thanks

[nrage]

The line of aim goes from the center of the actual white ball to the center of an imaginary or ghost white ball which you have to imagine sitting on the table touching the BOB spot you've chosen.