... The actual aim point difference between a 3/8 and a 1/3 aim is 0.09" at the OB. The offset angle (angle between the alignment line and the aim line) is close to 1° from full table distance on a 9' table, and around 5° when the CB is within a foot of the OB. This offset changes the actual cut angle of the shot by half of the offset.(a 30° cut from one foot away ends up being a 28° cut, while from 7 feet away it's a 29.5° cut). This offset angle climbs significantly faster as the CB gets closer to the OB. So when the balls are closer than about 8", the offset is already bordering approximately 10°, which means the a 30° cut angle will come off at 25°, too thick unless you're shooting into 5.5" bucket pockets. A thinner aim must be used at close distance. ...
Do you mean these statements about offset angles to apply just to half-ball aims or as generalizations? I certainly don't think they are accurate as generalizations. Offset angles vary not only with the distance between OB and CB (decreasing with increasing separation) but also with the basic thickness of cut (decreasing as the cut angle decreases). So for a given distance between CB and OB, the offset angle will be smaller for a 3/4-ball hit than for a 1/2-ball hit, and smaller for a 1/2-ball hit than for a 1/4-ball hit.
In the example he gave it says that for that example your system recommends 3/8 aimpoint and that for varying distance it would miss the pocket in 4/6 CB-OB distances, first two could be considered the ones at close distance which you are saying that need to be aimed thinner, what about the last two which are at 4 diamonds away and against the head rail?\
Do your recommended aim points work only for greater then 1 and less then 4 diamonds distance between CB and OB without any adjustments to pocket the ball anywhere in the pocket?
Mirza -- I believe my numbers are accurate given the precise assumptions I made. I calculated the numbers just as an example of how the necessary cut angle changes as the distance between the balls changes. Note how close the last two shots in that example are to working with the 3/8 hit. If the throw was slightly more than I assumed, or the pocket a bit larger than I assumed, the shots are pocketed.
You only need to aim thinner when the CB and OB are closer together. One aim point thinner when the distance is about 5 to 8", and as close as 3" you'd need two aim points thinner. The amount of angle offset from a greater distance is very minimal, so no aiming compensation is needed. ...
Brian, this post makes me think that when you talk about distances between balls you must mean edge to edge rather than base of ball to base of ball. Is that so? What I have posted uses base to base.
As for your last sentence, even when the separation between balls is large, I think some adjustment is needed sometimes. Here is another example of it
• OB -- one diamond straight out from a side pocket;
• CB -- against the end cushion, also one diamond out on the same side of the table;
• Target -- the far diagonal corner pocket.
Poolology's arithmetic says it's a 1/4-ball aim. That will produce a cut angle of 48.6° ignoring throw, or something in the range of maybe 45° - 48° accounting for throw. But the cut angle actually needed to pocket that shot is 38.5° to center pocket With a 4½" pocket accepting another 1.1° either way from that distance, let's say the OB must travel at an angle between 37° and 40°. An accurate 1/4-ball hit will overcut the shot.
I just plotted the shot on paper, cutting it to the right, then used a computer to check line accuracy and my angles. From one diamond distance out, a 3/8 hit provides a 38° shot to center pocket, not accounting for throw. Subtract a 1 to 2° throw and the ball goes thick, just left of center pocket, but clean in the hole. At 3 diamonds out a 3/8 aim provides 40° shot, slightly over-cutting to the right pocket edge...subtract for throw and the ball hits very close to center pocket.
So he's close, but not exact. The best test is to shoot the shot and rely on the results.
Brian, a 3/8-ball hit is a 38.7° cut regardless of the distance between the balls (ignoring throw). In my original post, I used 37° as the constant cut angle for all distances after allowing for throw. I agree that a 3/8 aim works on that shot from 3 diamonds. See my original post, or my next response here, for comments on the 1-diamond separation.
For AtLarge:
Here is the example you dissected. Though your theory is correct, your figures are not. ...
It's a 9ft table with 2.25" balls. Shooting this shot from the end rail is tough because distance makes it hard to accurately put the CB where you need it. But yes, a 3/8 aim works anywhere along the alignment line except when CB gets with 6 to 8 inches from the OB. And that's when a thinner hit is needed.
Yes, your pictures are for one of the shots I mentioned, but they really don't help determine or analyze fine differences in cut angles.
I believe my figures are correct given the precise assumptions I made. All the angles I mentioned were calculated by me. If you are so inclined, you could re-read my original post carefully, calculate some of the angles I used yourself, and let me know (perhaps by PM) of any discrepancies you find.
As for your last sentence, I think the 3/8 aim might not work from one diamond away. As I said in the original post, the OB must travel on a cut angle of about 40° ± 1½° with a 4½" pocket, whereas the 3/8-ball hit will cut it at 38.7° less throw (so maybe something like 37°). So it's close for sure. But I think it is a "thin" 3/8 (like a 1/3).
This stuff is fun, n'est-ce pas?