Maybe if I add a few dance steps, a pivot or two, a video...
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Easy way to measure an angle in degrees
- Thread starter Bob Jewett
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No I don't. You showed a very easy way to estimate or find the cut angle.
I misunderstood the thread. I thought it was a method to help determine where/how to aim a cut shot by knowing or figuring the angle. But you're just showing how to find the approximate angle when using ghostball, not how it relates to fractional aiming itself.
It would be something if the standard cue length is what is not because it helps players reach certain shots, but because someone centuries ago knew 57 to 59 inches would help with estimating angles. Interesting.
I think it is more accurate to call it "inch and an eighth" since the cue stick will pivot around the inch-and-an-eighth point which I think is a lot easier than imagining a ghost ball for a lot of people.
It turns out that the angle measurement is surprisingly tolerant of errors in picking the inch-and-an-eighth point for many shots. For a typical situation with the cue ball two diamonds from the object ball and about a 30-degree cut, if you are off by an inch on the placement of the point, the angle -- assuming you do the distance estimation correctly -- will be off by only a little over one degree.
The smaller the cut angle and the longer the shot, the less sensitive the system is to errors in the selection of the point. Fairly obviously, if the shot is straight in, the system says zero cut regardless of where along the shot line the chosen pivot point is.
If the cue ball is very close to the object ball and the cut angle is large, the angle will be more inaccurate for a given error in the pivot point.
Math makes my head hurt. But 19 inches equal 19 degrees, yeah. Thanks one more time Bob.
One further wrinkle to using this angle-measuring system is that it doesn't work well for thin cuts. If you have a 90-degree cut, the distance measured from bumper to bumper along a straight line between the two positions is 1.414*57". That's 80.6 inches or about 80 degrees instead of 90.
To get a more accurate answer, measure the smaller angle involved in the cut, which is shown in the diagram. It is how far from 90 degrees you are. You still use one cue stick position over the cue ball, but the other cue stick position is with the tip at the inch-and-an-eighth pivot point and perpendicular to the line of the shot. In the position shown, it's not hard to get the perpendicular correct -- other ball positions will be more challenging.
![CropperCapture[625].png](https://forums.azbilliards.com/data/attachments/410/410572-7e78667f16b8aa38e6e7d202cc72ec10.jpg "CropperCapture[625].png")
Anyway, if we have the same 19 inches and 19 degrees, we know the cut angle is 90-19 or 71 degrees. Rather than actually doing the subtraction to get a cut of 71 degrees, I think it's easier to just call the 19 degrees the "anti-cut" angle and leave it at that. The smallness of the anti-cut angle tells you how thin and difficult the shot is. It gives you a clue of how much overlap of the ball edges you need for those systems that pay attention to the edges for thin cuts.
(Technically, the anti-cut angle is properly called the "complementary angle" to the cut angle, since two angles that add to 90 degrees have that special name. 19 degrees is the complement of 71 degrees. We now return you to your regularly scheduled nearly math-free program.)
To get a more accurate answer, measure the smaller angle involved in the cut, which is shown in the diagram. It is how far from 90 degrees you are. You still use one cue stick position over the cue ball, but the other cue stick position is with the tip at the inch-and-an-eighth pivot point and perpendicular to the line of the shot. In the position shown, it's not hard to get the perpendicular correct -- other ball positions will be more challenging.
Anyway, if we have the same 19 inches and 19 degrees, we know the cut angle is 90-19 or 71 degrees. Rather than actually doing the subtraction to get a cut of 71 degrees, I think it's easier to just call the 19 degrees the "anti-cut" angle and leave it at that. The smallness of the anti-cut angle tells you how thin and difficult the shot is. It gives you a clue of how much overlap of the ball edges you need for those systems that pay attention to the edges for thin cuts.
(Technically, the anti-cut angle is properly called the "complementary angle" to the cut angle, since two angles that add to 90 degrees have that special name. 19 degrees is the complement of 71 degrees. We now return you to your regularly scheduled nearly math-free program.)
Yep, the same tolerance for error applies with fractional aiming also.
Place an ob anywhere between the footspot and the 2nd diamond from the corner pocket on the side rail. Now place the cb at least a foot from the ob with the centerline of the balls lined directly to the 1st diamond away from the pocket. A halfball aim will pocket the ball every time, regardless of where the ob is along that line, as long as the balls are aligned toward that 1st diamond. This shows how a 30° cut shot can be used quite often, despite the exact shot angle.
Of course, what's happening is use of the entire pocket, taking advantage of the fact that the pocket is twice as wide as the ball.
That's not true.
If I choose a half-ball hit for a 25-degree cut, the aim is not made more accurate by the cue ball being farther away. In the case of measuring the angle, the final error due to an error of the initial input is reduced by longer distances.
Lol. Why would you choose a halfball hit for a 25° shot?
I was simply saying that with fractional aiming there is some tolerance (acceptable error in aim) due to the acceptable margin of error at the pocket.
I'm not understanding what you are using this angle measurement to accomplish. It makes sense if you are suggesting to use this info in order to help determine a fractional aim line. But you haven't said that.
If you determine a shot angle is about 25°, you would not select a halfball hit for the shot. A touch thicker hit would be needed, of course. I think it's a great tool for that purpose.
My point was that if someone makes a mistake and sees as a half-ball shot one that is actually a 25-degree cut -- and there are people who will do that occasionally even if they try to follow closely a fractional ball aiming system -- then having the cue ball farther back will not decrease their angular error on the shot. I hope this much is obvious.
I find that when studying systems for anything, including aspects of pool, it is good to include in the analysis a study of what errors might come up and how much of a problem they might represent. That was my point in saying what I did. It was looking more deeply at the system.
Have you ever tried to do a similar thing for fractional ball aiming? Perhaps a separate thread for that would be better.
I think that angle estimation is a fundamental part of aiming. This is entirely separate from what aiming system a player uses on the shot.
Got it. And yes I've studied the effects of distance with fractional ball aiming. Well, at least how it affects the Poolology system.
With traditional fractional ball aiming (where you just estimate or guess which fractional line to use) distance does not make a difference. You look at the shot and estimate the angle, or use a cool system like you've shown here to figure out the angle, then you aim for the fractional overlap that produces that angle. Distance won't change the outcome. I mean a halfball hit is always 30° (regardless of distance) when you're referencing the ghostball or 1.125" behind the ob. In that respect I see great value in using your cue, inch by inch like you've shown, when it comes to determining the angle and estimating a fractional aim line to use. Knowing there's less error with distance when using this method is a plus also.
With Poolology, distance is a factor because there is no ghostball reference. The fractional aim is determined by the cb-ob relationship. So the closer the cb is to the ob the thicker the shot comes off (relating to the pocket) when using the aim line provided by the system. As long as the distance between cb and ob is about 15" to 50", the accuracy or distance factor is basically insignificant, less than 1° or so for most shots. With a greater distance between the balls the system provides an aim line that comes off a little thinner toward the pocket. There is a sweet spot around 2 to 3 feet where the system is most accurate.
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So, if someone never estimates a cut angle, are they aiming wrong?
The only thing needed to know about the cut angle is this.....
As the angle increase, less energy is transferred from the CB to OB.
Oh and what Ghostball?.......Never seen one......
I think all players estimate cut angles whether they put a number on them or not. I remember when I was first learning to play and for nearly full shots I thought about "just a little off straight". I didn't say "three degrees" although I knew enough geometry to figure that out.
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Series of Videos on cut angle determination
I created a set of 3 videos illustrating various methods to estimate the cut angle of a pool shot. These are on YouTube. The general title is AimRight - What's that cut angle?
This technique presented here is one of a set of ones using the cue stick to 'measure' the cut angle. It is illustrated in the second video (part 2) at about the 4 minute mark. Here's a link to the video: https://www.youtube.com/watch?v=qi_VhbaqlqY&t=439s
If the link doesn't work (or is deleted), simply go to YouTube and search for the AimPro Billiards channel and at that channel, you can find this series.
Regarding why someone would want to learn the cut angle, that is partly addressed in the video series. In short, one can learn to aim, based on the cut angle. (Note: practicing shots at known cut angles is a GREAT way to work on stroke mechanics at the same time as learning aiming.) Then one needs to be able to accurately estimate it, IF (it's optional) you want to use it in a game. Some shots like banks and especially combos aren't usually learned by memory and some 'method' is usually necessary. And by knowing the cut angle, one then is better able to USE the vast amount of pool mechanics analysis that usually tells you about throw and cue ball position info (direction and relative speed) as a FUNCTION OF THE CUT ANGLE and is usually presented as equations and shown in graphs. Some of this information was compiled by me in tables, for 16 cut angles, and is available in the AimRight User's Guide. It was derived from the equations from Dr Dave. (thanks again).
I created a set of 3 videos illustrating various methods to estimate the cut angle of a pool shot. These are on YouTube. The general title is AimRight - What's that cut angle?
This technique presented here is one of a set of ones using the cue stick to 'measure' the cut angle. It is illustrated in the second video (part 2) at about the 4 minute mark. Here's a link to the video: https://www.youtube.com/watch?v=qi_VhbaqlqY&t=439s
If the link doesn't work (or is deleted), simply go to YouTube and search for the AimPro Billiards channel and at that channel, you can find this series.
Regarding why someone would want to learn the cut angle, that is partly addressed in the video series. In short, one can learn to aim, based on the cut angle. (Note: practicing shots at known cut angles is a GREAT way to work on stroke mechanics at the same time as learning aiming.) Then one needs to be able to accurately estimate it, IF (it's optional) you want to use it in a game. Some shots like banks and especially combos aren't usually learned by memory and some 'method' is usually necessary. And by knowing the cut angle, one then is better able to USE the vast amount of pool mechanics analysis that usually tells you about throw and cue ball position info (direction and relative speed) as a FUNCTION OF THE CUT ANGLE and is usually presented as equations and shown in graphs. Some of this information was compiled by me in tables, for 16 cut angles, and is available in the AimRight User's Guide. It was derived from the equations from Dr Dave. (thanks again).
Great information and video presentation.
I don't think I've ever cared to know the exact angle of any cut because it doesn't matter. Outside of thinking is this a thick cut, thin cut or really thin (consider a safety), there's no other consideration that's required to make the ball and run out.
Easy way to not measure any angle is just pivot aim and worry about your position speed instead.
Easy way to not measure any angle is just pivot aim and worry about your position speed instead.
Lacking insight doesn’t mean the knowledge isn’t useful. Just because we can’t see around a corner doesn’t mean nothing is there. Awareness is about seeing things right under our nose and figuring out its significance. Picking lint/debris up off the table near the cb and/or ob and on the path to the pocket is an example. Those flecks of chalk are small compared to the enormous balls and huge pockets. How can such small things have such a huge impact on perception? WorkIng with information, rather than dismissing it, seems a good strategy, don’t you think? We are often reminded that the devil is in the details.
From straight in to a quarter ball cover about 49 of the 90°. Line up a cue center to center on the ob and set down a chalk on the table at the end of the butt. Now line up a cue from ob to pocket and estimate the distance from the butt end to the chalk in inches. That will give you a rough idea of the angle. My cue is 58”. Swinging my cue from its butt location to the chalk gives me a measure. Now how many more inches is the chalk away from the tip. If it’s a foot the angle is about 60°. There are a 30° more angles still in that last ~ ⅛ of the ball. Do you have another way to know and recognize a 72 to 75° shot?
Thanks again Bob for focusing our awareness on what we might have missed right under our nose.