Are fixed-line of aim, fractional-ball aiming systems useful?
and in part 2 of NV B.3 – Mike Page’s aiming video (part 1, part 2). For more info, see: “HAPS – Part I: Fractional-Ball Aiming” (BD, November, 2014).
Also, here’s a useful illustration from “Aim, Align, Sight – Part I: Introduction and Ghost Ball Systems” (BD, June, 2011) defining the standard ball-hit fractions:
And here are ball layouts one can use to set up the standard ball-hit fractions at a table (from “HAPS – Part I: Fractional-Ball Aiming” – BD, November, 2014, and “Aim, Align, Sight – Part I: Introduction and Ghost Ball Systems” – BD, June, 2011):
The illustration below (from Patrick Johnson) shows the approximate cut angles for all standard ball-hit fractions. For more information on how ball-hit-fraction is related to cut angle, see the ball-hit fraction vs. cut angle resource page. TP A.23 – Ball-hit fraction vs. cut angle shows equations and plots for all ball-hit fractions and cut angles. See estimating cut angles and below for other methods to visualize fractional-ball cut angles.
Various aiming systems (even though they are not perfect) do help some people aim, concentrate, focus on the OB, stay down, and shoot better. I don’t think anybody (even me) would say that is a bad thing. On the other hand, people should realize that fixed-point aiming systems with a limited number of aiming lines are not perfect and will cause you to miss shots if you don’t compensate (consciously or subconsciously).
The common fractional-ball aiming system, sometimes referred to as Hal Houle’s 3-angle system. Basically, the claim is there are only three different aims for all cut shots: a “15° cut,” a “30° cut,” and a “45° cut.” In TP A.11, I show that these aims are equivalent to 3/4-, 1/2-, and 1/4-ball-hits and the 15- and 45° angles are not exact. Also, I show an example shot “in between” two of the aim references to show a deficiency of the method. The method provides easy visual aiming, and it helps a player establish good reference aims for different ranges of cut shots; but for “in-between” cut angles, one must adjust or compensate between the aim references.
Fractional-ball aiming references (1/4, 1/2, and 3/4), on either the CB or OB, can be useful to help some people aim because the references are easy to visualize. However any system that offers only a limited number of lines of aim from which to choose can be limiting if the user isn’t good at adjusting for the many shots that fall between these references. For more info, see: limited lines or alignments of aim. Also, any “aiming system” can offer a person benefits, especially a person that doesn’t aim accurately or consistently.
from Patrick Johnson (in AZB post and via e-mail):
To use Fractions for aiming you need to get familiar with (learn to visualize at the table) the cut angles formed by the three common fractional overlaps: 3/4, 1/2 and 1/4 ball. To help with that, here’s a practice setup diagram of the fractional cut angles (left and right) for shots parallel with the short and long rails.
Your hand can be a useful guide for estimating the cut angles made by fractional CB/OB overlaps. Just spread your fingers as far as possible so the thumb and little finger form a 90° angle, and your other three fingers space themselves more of less naturally on the three major fractional cut angles (roughly 15, 30, and 45° – actual fractional cut angles shown below).
To cover the rest of the 90° “aiming field,” cut angles for two more (less frequently used) fractional overlaps are shown in black.
Use your other hand to estimate cuts in the other direction.
Like all “discrete”, “fractional-ball”, and similar aiming systems, it gets you in the ballpark for most shots and depends upon subconscious correction to make the fine adjustments. In other words, you have to use it as a guide, “take it on faith”, and shoot the shots.
For a beginner, it will get them in the ballpark and they’ll accidentally pocket more balls than by winging it. For an intermediate, they may have enough experience that they will subconsciously correct, and the system might work well for them. The expert doesn’t need a system to get them in the ballpark.
All discrete systems have the same failing – they are not geometrically correct for all setups. If you claim that there are only a (small) discrete number of aim points required to hit any pocket from any setup, and disallow the subconscious correction factor, all such systems may be easily disproven. In practice, your ability to compensate overcomes the built-in flaws of the system.
from Hal Houle:
When cutting to the left for 15°, aim the cue ball’s left edge at the object ball’s left quarter. When cutting to the left for 30°, aim the cue ball’s left edge at the object ball’s center. When you cut to the left for 45 degrees, aim the cue ball’s left edge at the object ball’s right quarter. When you cut to the right for 15°, you aim the cue ball right edge at the object ball’s right quarter. When you cut to the right for 30°, you aim the cue ball’s right edge at the object ball’s center spot. When you cut to the right for 45°, you aim the cue ball’s right edge to the object ball’s left quarter.