AzBilliards.com Fractional Aim Lines - Quick Way to Recognize Dead Shots
 Fractional Aim Lines - Quick Way to Recognize Dead Shots
 (#1) BC21 Poolology     Status: Offline Posts: 3,433 vCash: 500 iTrader: 2 / 100% Join Date: Feb 2017 Location: West Virginia Fractional Aim Lines - Quick Way to Recognize Dead Shots - 11-05-2019, 07:57 AM Here is quick way to recognize some dead shots. Anytime the cb and ob are lined up straight in to the rail, meaning the line between the balls is parallel to the side rails, these lines indicate the fractional aim needed to pocket the ob in pocket "A". In the blue highlighted example the ob is on the 1/2 ball line and the cb and ob are lined straight/perpendicular to the end rail. This is a 1/2 ball shot. If the ob were on the 3/4 line and the balls were lined straight up then it would be a 3/4 ball shot, and so on. If the balls aren't lined straight/perpendicular to the end rail, then figuring the aim works like this: Whatever distance the ob happens to be from the side rail (on the targeted pocket side of the table) is where the cb to ob line should hit in order for the shot to be a dead 1/2 ball or 3/4 or whatever fractional line the ob is resting on. Call this spot "X". So if the cb to ob line is leading to a spot on the rail that is halfway between the targeted pocket and X, the fractional aim is halfway between a dead straight on hit and whatever fractional aim line the ball is resting on. In the example shown, the ob is resting on the 1/2 ball line. The balls are lined straight/perpendicular to a spot 2.5 diamonds from pocket A. If the cb to ob line pointed to a spot on the rail 1.25 diamonds from A (which is half of 2.5) then this would be a 3/4 ball shot. Every 1.25 diamonds (for this particular shot) is a 1/4 fractional aim difference. So if the cb-ob line were pointed to 3.75 diamonds from A, this would be a 1/4 ball shot. The yellow line works the same way for a 1/2 ball bank shot to "B". This method can be figured for side shots, bank shots, etc... It's really easy and useful when the two balls are lined straight/perpendicular to the end rail. Else it gets a bit tricky. POOLOLOGY YouTube Brian Crist Last edited by BC21; 11-05-2019 at 07:59 AM.

 Rosie....Rosie....Rosie
 (#2) Low500 Banned   Status: Offline Posts: 1,640 vCash: 500 iTrader: 0 / 0% Join Date: Apr 2017 Rosie....Rosie....Rosie - 11-05-2019, 09:26 AM Rosie to the rescue..............
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11-05-2019, 09:55 AM

Quote:
 Originally Posted by Low500 Rosie to the rescue.............. (unrelated/meaningless picture omitted)
Wag wag little puppy.

POOLOLOGY
Brian Crist

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JoeyInCali
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11-05-2019, 10:36 AM

Quote:
 Originally Posted by BC21 Wag wag little puppy.
Is Low 12 years old?

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11-05-2019, 10:49 AM

Quote:
 Originally Posted by JoeyInCali Is Low 12 years old?
Lol. Mentality wise...it sure seems like it.

POOLOLOGY
Brian Crist

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11-05-2019, 11:59 AM

Quote:
 Originally Posted by BC21 Wag wag little puppy.
Okay...okay, okay. I know you're impatient and want your treat. Here 'tis...

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11-05-2019, 12:01 PM

Quote:
 Originally Posted by JoeyInCali Is Low 12 years old?
Mr. Bautista, sir.
The name here is "LOW IQ"....get it right, por favor.
(Please try to keep up. Thank you for calling)

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11-05-2019, 06:28 PM

Quote:
 Originally Posted by Low500 Mr. Bautista, sir. The name here is "LOW IQ"....get it right, por favor. (Please try to keep up. Thank you for calling)
Bautista? Is that JoeyInCali's last name? Come on JLB, you can tell me. Lol

POOLOLOGY
Brian Crist

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sixpack
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11-05-2019, 06:56 PM

Quote:
 Originally Posted by BC21 Here is quick way to recognize some dead shots. Anytime the cb and ob are lined up straight in to the rail, meaning the line between the balls is parallel to the side rails, these lines indicate the fractional aim needed to pocket the ob in pocket "A". In the blue highlighted example the ob is on the 1/2 ball line and the cb and ob are lined straight/perpendicular to the end rail. This is a 1/2 ball shot. If the ob were on the 3/4 line and the balls were lined straight up then it would be a 3/4 ball shot, and so on. If the balls aren't lined straight/perpendicular to the end rail, then figuring the aim works like this: Whatever distance the ob happens to be from the side rail (on the targeted pocket side of the table) is where the cb to ob line should hit in order for the shot to be a dead 1/2 ball or 3/4 or whatever fractional line the ob is resting on. Call this spot "X". So if the cb to ob line is leading to a spot on the rail that is halfway between the targeted pocket and X, the fractional aim is halfway between a dead straight on hit and whatever fractional aim line the ball is resting on. In the example shown, the ob is resting on the 1/2 ball line. The balls are lined straight/perpendicular to a spot 2.5 diamonds from pocket A. If the cb to ob line pointed to a spot on the rail 1.25 diamonds from A (which is half of 2.5) then this would be a 3/4 ball shot. Every 1.25 diamonds (for this particular shot) is a 1/4 fractional aim difference. So if the cb-ob line were pointed to 3.75 diamonds from A, this would be a 1/4 ball shot. The yellow line works the same way for a 1/2 ball bank shot to "B". This method can be figured for side shots, bank shots, etc... It's really easy and useful when the two balls are lined straight/perpendicular to the end rail. Else it gets a bit tricky.
Thank you. This is useful.

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 (#10) Vorpal Cue Just galumping back     Status: Offline Posts: 349 vCash: 500 iTrader: 0 / 0% Join Date: Sep 2016 Location: Tulgy Woods 11-06-2019, 11:43 AM Your angles are a little off. A corner to corner line is 27*. A right triangle with a 4 diamond base and 7 diamond length is much closer. The arc tan of 4/7 is 29.7*. The line from the 7th diamond to the corner is a better fit. The 45* cut is a 1/16 ball off also. My Vorpal cue jabbed 'er wonky and the shot went snicker-snack. 'Twas brillig.
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11-06-2019, 12:19 PM

Quote:
 Originally Posted by Vorpal Cue Your angles are a little off. A corner to corner line is 27*. A right triangle with a 4 diamond base and 7 diamond length is much closer. The arc tan of 4/7 is 29.7*. The line from the 7th diamond to the corner is a better fit. The 45* cut is a 1/16 ball off also. Attachment 533758
Nope. What you are showing is merely table geometry which doesn't account for cb-ob relationships. What I am showing accounts for the aim line from cb to ob.

Set a ball on your 1/2 ball line and place the cb a couple of diamonds away, both balls straight/perpendicular to the end rail. Aim for a 1/2 ball hit and you'll miss the pocket by half a diamond, too thick. Now set the same shot up on my 1/2 ball line. The ob hits the pocket. My line 26.6°. But when you account for the angle the cb needs to travel (away from the cb-ob center to center line), the cut angle is very close to 30°.

POOLOLOGY
Brian Crist

Last edited by BC21; 11-06-2019 at 12:36 PM.

 (#12) Vorpal Cue Just galumping back     Status: Offline Posts: 349 vCash: 500 iTrader: 0 / 0% Join Date: Sep 2016 Location: Tulgy Woods 11-06-2019, 12:37 PM So the balls present themselves differently and the geometry doesn't work when a cue ball is added? My Vorpal cue jabbed 'er wonky and the shot went snicker-snack. 'Twas brillig.
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11-06-2019, 12:48 PM

Quote:
 Originally Posted by Vorpal Cue So the balls present themselves differently and the geometry doesn't work when a cue ball is added?
No. Maybe this will explain it: The lines you show represent the correct angles based on cb center through ob center. But shot angles are measured from the cb to through the GHOSTBALL center. This means all the lines you are showing will be off by a few degrees, depending on the distance between the cb and the ob.

When both balls are lined straight/perpendicular to the end rails (parallel to the side rails), the cb perspective must shift to whatever fractional aim is needed. If the ob is on the 1/2 ball hit line, your rendition has the 30° angle based on a center cb to center ob perspective. When you actually aim the shot your perspective shifts to a center cb to center ghostball or edge of ob perspective. The 30° shot shifts as well. The shift is dependent on the distance between the balls. If the distance is 2 diamonds (25"), the shift in perspective is about 2.6° (the angle difference between shooting at ob center and ob edge, which is....atan(1.125/25) = 2.58°). This means your 1/2 ball shot will land 2.6° away from the pocket. My lines account for this change in perspective.

And the yellow 1/2 ball bank line accounts for change in perspective and the cut-induced spin that typically causes these banks to come up short.

POOLOLOGY
Brian Crist

Last edited by BC21; 11-06-2019 at 11:57 PM.

 (#14) anbukev AzB Silver Member   Status: Offline Posts: 162 vCash: 500 iTrader: 0 / 0% Join Date: Aug 2011 11-08-2019, 09:47 PM I think Brian is explaining this: Attached Images
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11-09-2019, 11:01 AM

Quote:
 Originally Posted by anbukev I think Brian is explaining this:
The 1/2 line shown is not a 30° angle. It's 26.6°.

7/8 line is ATAN(1/8) = 7.0°
3/4 line is ATAN(2/8) = 14.0°
1/2 line is ATAN(4/8) = 26.6°
1/4 line is ATAN(4/4) = 45.0°

Now, the change in perspective from the cb-ob line to the appropriate fractional aim line is....

ASIN ((aim point distance from center ob) / (distance between cb and ob centers))

So if an ob is sitting anywhere on the 1/2 ball line, and the cb is 18" away, the change in perspective from this 26.6° angle is ASIN(1.125/18)=3.6°. The initial 1/2 line at 26.6° plus the 3.6° change in aiming perspective puts the shot on a 30.2° line to the center of the pocket.
Aiming for a half ball hit creates a 30° cut, so we are going to slightly overcut this ball by 0.2°, plenty good enough even with a +/- 1° margin of error.

For a +/- 1° margin of error (when the ob is at least 60" or so away from the pocket) the distance between cb and ob needs to be 14 to 27 inches in order to work. When the ob is within about 30" of the pocket then a workable cb to ob distance is anywhere from 12 to 46 inches. Basically, this method works fine from anywhere as long as the distance between cb and ob is within 1 to 2 diamonds, and if the ob is within 30" of the pocket then the cb to ob distance can be much greater.

It works the same the way for thinner or thicker cuts. But for thinner cuts the distance between cb and ob needs to be between 21 to 37 inches to stay with a +/- 1° margin. For a +/- 2° margin the distance can be 17 to 60 inches.

It is more accurate if we use a 25° angle for the 1/2 ball reference line, which is what I did in the Poolology system to allow room for ob throw. Instead of the 1/2 ball diagonal line going from center pocket to center pocket, it should go from the center of the target pocket to about a quarter diamond short of the diagonal corner pocket (on the short rail). But either way is workable.

POOLOLOGY
Brian Crist

Last edited by BC21; 12-05-2019 at 08:22 AM.

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