[BC21]

Originally Posted by Bob Jewett

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.

[Bob Jewett]

Originally Posted by BC21

Lol. Why would you choose a halfball hit for a 25° shot? ...

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.

[BC21]

Originally Posted by Bob Jewett

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.

[duckie]

Originally Posted by Bob Jewett

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.

So, if someone never estimates a cut angle, are they aiming wrong?

[duckie]

Originally Posted by BC21

The exact angle doesn't much matter if you're using the ghostball, which is what is shown in the 19° example. I mean, if you can recognize where the cb needs to be, using the ghostball method, then knowing the exact angle is insignificant -- just aim for the ghostball.

Another way to estimate the angle, or better yet the cb-ob relationship, is here.....https://youtu.be/C_lxXEFzCG0. The method doesn't involve estimating inch by inch from 60 inches away. It simply uses a hand distance and a ball's width to help determine the fractional aim lines, not exact angles or measurements that need to be calculated.

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......

[Bob Jewett]

Originally Posted by duckie

So, if someone never estimates a cut angle, are they aiming wrong?

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.

[AimPro Billiards]

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).

[BC21]

Originally Posted by AimPro Billiards

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.

[SpiderWebComm]

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.

[Imac007]

Originally Posted by SpiderWebComm

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.

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.

[Bob Jewett]

Maybe finally....

In any analysis of a system or method or estimation, it's good to see how much error is built in. Here is a table of the actual angle of the cut and then the inches between cue bumper locations, the inches for the "anti-cut" measurement described above for cuts over 45 degrees, and the anti-cut measured cut angle.

This is calculated for a cue stick that is 58 inches long which is a more common length than the ideal 57 and a little bit.

The last column is the error which is just the difference between the angle and the inches (using the anti-cut after 45 degrees).

The maximum error is only a fraction of a degree. I think that's pretty good for a method that requires little math. Of course the ability of the player to estimate distances is very likely to give larger errors than this angle-measuring method, so the method itself is probably not going to be a limiting factor.

[AimPro Billiards]

Respectfully, my excel spreadsheet shows different numbers (bigger errors)? What equation did you use?

[Bob Jewett]

Originally Posted by AimPro Billiards

Respectfully, my excel spreadsheet shows different numbers (bigger errors)? What equation did you use?

The distance I use is shown in the diagram in post 2 in this thread. Also note that I'm using 58 inches for the cue stick which will tend to reduce the error for the larger angles although it slightly increases the error for small angles. Still, there's always the possibility of an equation error somewhere.

For a 45-degree cut, the distance in inches between the two bumper positions will be 58*sin(45/2)*2. By my calculation, that comes out as 44.391278 inches.

[AimPro Billiards]

I use this excel formula:
=+$A$2*SIN(C10*PI()/180)

With $A$2 being 58
C10 holding the angle in degrees

For 40°, I get 37.3".

If I compute the arc, for 40°, I get 40.5". Neither match your numbers. I'm confused.

[Bob Jewett]

Originally Posted by AimPro Billiards

I use this excel formula:
=+$A$2*SIN(C10*PI()/180)

With $A$2 being 58
C10 holding the angle in degrees

For 40°, I get 37.3".

If I compute the arc, for 40°, I get 40.5". Neither match your numbers. I'm confused.

I use the base of an equilateral triangle for the length. That's where the two factors of 2 come from. Evidently you are using a perpendicular dropped from one of the bumper positions to the other line. My distance will have about a quarter of the error of your method.