dr_dave said:
If you truly have this:
then I think you should re-post your complete description for comment again. I'm sorry, but I don't remember ever reading about any system that can truly do what I describe above (without special equipment or aids), and is practical for most people to use. I'm not saying your system doesn't satisfy these requirements, but I don't know unless you post a thorough description.
To answer your question, I would be willing to offer what it is worth if I think it could help me and others.
Thanks,
Dave
OK, here goes, I'll even throw in a pivot shift step.
Item 1: It is possible (with a little practice) to estimate cut angle to within about 1 degree accuracy. It does not require any illegal equipment, but a mark of some sort (I use hole reinforcers) placed on the cue stick 16 and 31 inches from the distal edge of the ferrule is helpful. When the aim line is established with the cue stick, is passes thru the centers of the pocket, OB, and GB. Establish this line with the cue tip just under the overhang of the OB (without bumping it, of course). Drop a line from one of these these cue reference points to the CB-OB line, and perpendicular to the CB-OB line. Estimate the distance of this perpendicular in inches. It is legal to use your hand to estimate this distance if you choose.
If you measured from the 16" point, multiply by 4
If you measured from the 31", multiply by 2
If you measure 3" off the cue butt, multiply by 1
This yields the cut angle, at the GB center, in degrees. Don't proceed until you are comfortable that you can do this accurately.
Item 2: For cut angles up to 30 degrees, the correct "target point" on the OB is 1mm off center for each degree of cut angle. Note that this target point is on the 2-D disc (plane) passing through the center of the OB, viewed from the CB. For cuts over 30, up to 50 degrees, I use about 4 mm for every 5 degrees of cut beyond 30 degrees.
If you can estimate mm distances well, you are set to fix on the target. If you can't, some clockface reference points are: 15 degrees--> 5 or 7 o'clock, 20 degrees--> 7:30 or 4:30, 25 degrees-->8:00 or 4:00.
Or,
Item 3: To find the target point on the OB using shift-pivot-shift, proceed as follows using that convenient 13mm measuring stick at the tip of your cue"
1) Align cue along centers of CB-OB line, with tip slightly off the CB
2) Using the CUE BALL find where the target point would be on the CB "side of the cut", as if it were the OB. Example: suppose you had a shot that was a 13 degree cut to the left. Using the cue tip as a measuring device (one tip width = 13 mm), put the center of the tip aligned with the point 13mm to the left of center on the CUE BALL. As you do this, parallel-shift the cue to point at the desired point on the CB.
Now pivot (pivot point at cue-tip) to aim to center of the OBJECT BALL, then parallel-shift the cue "back to center" so the tip is now pointing thru CB center. Your cue is now aligned thru CB center, and a point 13mm to the right of center on the OB, which is the desired aim line. Fire away. You should get your 13 degree left cut.
Summary:
1) Estimate cut angle in degrees, as described.
2) For angles 0-30 degrees, target the OB 1mm off center for each degree of cut. Because it is easier to estimate mm distances close-up, the appropriate distance can be found on the CB, and thru the shift-pivot-shift sequence described, the CB center and OB target line can be established.
3) The 1mm=1 degree relationship doesn't hold beyond 30 degrees. Up to 50 degrees, I use about 4mm per 5 degrees of cut. Beyond 50 degrees, I am looking for another shot, or using the overlap method, as I personally find it difficult to aim at distances far off the OB.
That is it. Guaranteed to be geometrically correct.
Like anything, it takes some practice.
