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View Full Version : Astigmatism and scope question


problemchild
08-29-2010, 2:37 PM
What happens when a person with AS shoots a rifle with a scope. It seems my POI is not the same as my POA. When my buddy gets behind my rifle he shoots small groups and when Im shooting I get some small but most scattered. The gun is not moving so it has to be my bad eyes.

Are there any type of scopes that work better with an astigmatism? Would an acog be better then a 10x scope?

FLIGHT762
08-29-2010, 5:32 PM
Most scopes have a diopter adjustment. ACOGs, Red dot sights(Eotech,Aimpoint etc) DO NOT.

I have Astigmatism. I spoke to an ACOG rep. once about this,who told me their scopes are made for young eyes! When I look through a red dot sight, I get a 45 degree football, even with my glasses. I still shoot well with them, those of us with Astigmatism are out of luck. I just have to live with it for those types of sights.

My regular scopes with diopter adjustments adjust and allows me to see the reticle clearly.

As far as my POA to to someone else's POI, I don't worry about when someone else shoots the rifle. I can shoot very small groups, my Astigmatism doesn't effect my accuracy in a scope with a diopter adjustment. Without a diopter adjustment, I'm not going to see the reticle or dot clearly and that can affect my groups.

problemchild
08-29-2010, 6:09 PM
Hmmm

So why would my POI be hopping all over when my crosshairs never leave the center?

bruce_ventura
08-29-2010, 8:07 PM
Unless your astigmatism is severe, it's probably not the problem. The problem could be a related to number of shooter-specific issues: experience, shooting position, trigger control, parallax, anticipating recoil, etc.

Do you wear correction when shooting? how big are your groups vs your friends (give the range)?

k1dude
08-29-2010, 8:27 PM
I have an astigmatism and when I look through red dots they are always blurred. But I got to look through an ACOG TA31 for the first time a few weeks ago and could not believe how crisp and clear it was! The donut and all the markings were clear as day. After that experience I've been saving my pennies for a TA11H.

Traditional scopes with parallax adjustment are better than those without for my accuracy.

ojisan
08-29-2010, 8:29 PM
^ Save your pennies for Lasik.
;)

Mail Clerk
08-30-2010, 5:17 AM
What happens when a person with AS shoots a rifle with a scope. It seems my POI is not the same as my POA. When my buddy gets behind my rifle he shoots small groups and when Im shooting I get some small but most scattered. The gun is not moving so it has to be my bad eyes.

Are there any type of scopes that work better with an astigmatism? Would an acog be better then a 10x scope?

problemchild,

I have AS really bad and usually have no issues in dealing with the eye condition. If you can't focus on the cross hairs then it indicates your eye is tired and you need to relax and look at something else to focus on for about two to five minutes. Perhaps you need to re-focus/adjust your scope to your aiming eye??? OR maybe your looking too close or too far away from the rear of the scope???? Have you considered those?

Using my red dot electronic sights I onlt turn it up brightly as needed and no more. Too bright not good to little not good either.

Mail Clerk

problemchild
08-30-2010, 7:20 AM
A few details.

Shooting at 100 yards.
I can on occasion shoot sub 1/2 inch groups.
My trigger is a Geissle Match set to less then 1lb.
Rifle is LMT308
I can group my handloads at 1-1.5 inch sometimes followed by 2-3" the next group doing the exact same thing.
I grouped GFMM yesterday at 2.5 inch.
My neighbor, who has no experience and who has never fired my rifle, shot a 3/4 inch group with FGMM. He also has 20 year old eyes (27).
He grouped my handloads at 1" while I was grouping my handloads at 2"

Bottom line is my rifle was sandbagged for both of us and rock stable. I am very comfortable shooting and never slap the trigger. My crosshairs dont move off center. I taught my neighbor how to shoot using my techniques and he shot sub moa on the second 5 rd group.

It has to be my eyes. I see two sets of crosshairs at the center even with glasses. I can adjust it out but it comes back so I stopped trying. I did look through and Acog and it was very clear but the right side faded off.

Im pretty sure my technique is solid but I am open for suggestion.

Mail Clerk
08-30-2010, 7:34 AM
problemchild,

Based on your info your eyes are getting too tire when you look through the scope! I believe your staring too long into the rear of the scope. I highly sugget you refocus the scope so it'll be more confortable for you. When you take aim how long do you stare/aim before you take a shot????

Mail Clerk

problemchild
08-30-2010, 10:39 AM
problemchild,

Based on your info your eyes are getting too tire when you look through the scope! I believe your staring too long into the rear of the scope. I highly sugget you refocus the scope so it'll be more confortable for you. When you take aim how long do you stare/aim before you take a shot????

Mail Clerk

I do not think so as it happens right away.

bruce_ventura
08-30-2010, 11:06 AM
Based on your response, I agree that technique is looking less likely. Just grabbing at low-hanging fruit.

GFMM? FGMM? Please explain.

What model scope do you have mounted on that bad boy? Does it have adjustable objective (AO) focus?

How many shots in your group? For just three shots the difference between 1" and 2" may not be statistically significant. I usually shoot a group of five to get reproducible group sizes.

Two sets of crosshairs? That is sometimes what astigmatism looks like when out of focus (I have very weak astigmatismin one eye). Have you tried different diopter settings on the eyepiece? Try to focus the crosshair, not the scene behind it.

problemchild
08-30-2010, 12:27 PM
Based on your response, I agree that technique is looking less likely. Just grabbing at low-hanging fruit.

GFMM? FGMM? Please explain.

What model scope do you have mounted on that bad boy? Does it have adjustable objective (AO) focus?

How many shots in your group? For just three shots the difference between 1" and 2" may not be statistically significant. I usually shoot a group of five to get reproducible group sizes.

Two sets of crosshairs? That is sometimes what astigmatism looks like when out of focus (I have very weak astigmatismin one eye). Have you tried different diopter settings on the eyepiece? Try to focus the crosshair, not the scene behind it.

FGMM= Federal gold medal match (168gr .308)

If adjust for parallax my focus goes out. If I adjust for focus my parallax goes out. I cannot get a focused target, reticle and be parallax free. Bad thing is I am right handed and my right eye is the bad eye.
This is the scope I am using.
http://swfa.com/SWFA-SS-10x42-Tactical-Riflescope-P500.aspx

FLIGHT762
08-30-2010, 2:00 PM
One last question. Have you properly focused the diopter adjustment for the crosshair properly? Some people don't know how to do this. Reticle focus and target focus are two different things.

To properly focus your crosshair for your eye, you look throught the scope at a blank white wall. You look at your crosshair only and focus the diopter on the eyepiece (rotating it clockwise or counter clockwise) until the crosshair is in focus. DON'T LOOK AT THE WALL! LOOK AT THE CROSSHAIR.

After adjusting the crosshair focus, You can then move the scope to a distant target and then adjust your TARGET focus with the focus knob on the scope at the 9 O'clock position.

I was helping a shooter on our team one morning. He wasn't getting good groups and didn't know what was wrong. I looked through his scope and the diopter(crosshair focus ) was way out of focus. I adjusted it until he could see the crosshair clearly. That was all it was.

You may have done this already, but I thought I'd take a chance and ask.
Just remember,the diopter focus for your eye will be different than your Buddy's eyesight.

When I shoot my friend's Tac Ops Echo with his S & B 5X25X56 P II, I have to rotate the diopter(eyepiece) 1/4 turn or so to get the crosshair in focus for me. After I shoot, I rotate it back to his position.

I hope this helps you.

bruce_ventura
08-30-2010, 2:24 PM
I sounds to me like your vision correction is off. Could also be your shooting position is causing you to use a poor part of your glasses. Do you use progressive lenses?

How old are you and when was your last vision exam?

What do you mean when you say you "adjust for focus"? When I adjust an AO scope, I first adjust the diopter to get a comfortable reticle focus. Then I adjust the objective to get the target in focus. I check for parallax by moving my eye left and right with the rifle resting on bags. If the reticle and the aimpoint stay together, the scope is parallax-free. If the reticle moves off the aimpoint when I move my eye left or right, I re-adjust the objective.

How many shots in your group?

Fyathyrio
08-31-2010, 2:45 AM
Perhaps shooting off hand to use the other eye will help you diagnose if it's sight or scope issues?

problemchild
08-31-2010, 5:21 AM
One last question. Have you properly focused the diopter adjustment for the crosshair properly? Some people don't know how to do this. Reticle focus and target focus are two different things.

To properly focus your crosshair for your eye, you look throught the scope at a blank white wall. You look at your crosshair only and focus the diopter on the eyepiece (rotating it clockwise or counter clockwise) until the crosshair is in focus. DON'T LOOK AT THE WALL! LOOK AT THE CROSSHAIR.

After adjusting the crosshair focus, You can then move the scope to a distant target and then adjust your TARGET focus with the focus knob on the scope at the 9 O'clock position.

I was helping a shooter on our team one morning. He wasn't getting good groups and didn't know what was wrong. I looked through his scope and the diopter(crosshair focus ) was way out of focus. I adjusted it until he could see the crosshair clearly. That was all it was.

You may have done this already, but I thought I'd take a chance and ask.
Just remember,the diopter focus for your eye will be different than your Buddy's eyesight.

When I shoot my friend's Tac Ops Echo with his S & B 5X25X56 P II, I have to rotate the diopter(eyepiece) 1/4 turn or so to get the crosshair in focus for me. After I shoot, I rotate it back to his position.

I hope this helps you.

I will try this and post back.

problemchild
08-31-2010, 8:07 AM
OK I adjusted my diopter for scope use without my glasses. Im afraid the diopter needs to go in about 1/2 turn more then it allows. I hit the stop before I get a crystal clear reticle. Also when I adjust for parallax at a know distance the target is fuzzy.

I guess I need to shoot with my glasses on huh?

bruce_ventura
08-31-2010, 9:37 AM
I guess I need to shoot with my glasses on huh?

Uh... yea. I asked you this question in my first post. Starting off with corrected vision is fundamental to good shooting.

The diopter adjustment can only correct for myopia/hyperopia, not astigmatism. It sounds like you have a pretty strong prescription, with a combination of astigmatism and focus correction.

If you're over fifty and haven't had a vision exam in two years, you should get a thorough retinal exam and a new pair of glasses. Shooting high power rifles may put you at higher risk of a detached vitreous humor or detached retina (no conclusive data either way, but why take the risk?).

problemchild
08-31-2010, 5:40 PM
Uh... yea. I asked you this question in my first post. Starting off with corrected vision is fundamental to good shooting.

The diopter adjustment can only correct for myopia/hyperopia, not astigmatism. It sounds like you have a pretty strong prescription, with a combination of astigmatism and focus correction.

If you're over fifty and haven't had a vision exam in two years, you should get a thorough retinal exam and a new pair of glasses. Shooting high power rifles may put you at higher risk of a detached vitreous humor or detached retina (no conclusive data either way, but why take the risk?).

I had an exam 4 mo's ago. Sorry I forgot to comment on your post. I have a pair of maui jim polarized glasses that cost a fortune. Very high quality. I also have a pair of Zeiss clear glasses for night driving.

bruce_ventura
09-01-2010, 9:30 PM
I'm not sure what your point is. Unless the maui jim or Zeiss glasses have your prescription, use your regular prescription glasses for shooting instead.

problemchild
09-03-2010, 6:42 PM
I'm not sure what your point is. Unless the maui jim or Zeiss glasses have your prescription, use your regular prescription glasses for shooting instead.
Yes they are prescription