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POA/POI and focal plane problems

 
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  #1  
Old 12-08-2003, 06:14 AM
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Join Date: Dec 2003
Location: NZ
Posts: 13
POA/POI and focal plane problems

Hi,

I am not sure if any of you experienced this before but this happened to me a few times before.

Line up a target, dial in, pull the tigger and bang on. Spotter calls out another 5 targets the size of 2" square blocks and they get pulverised, just as easy.

Very precise shooting and I'm very pleased with myself.

Then the sun pulls out of the clouds and suddenly I am not hitting the targets anymore. I checked my water bubble and my gun was canted. I straighten it and the target disappear out of my focal plane.

The only way I could see the target was to cant and my bullets are going over at 1 O'clock high.

Same thing happened a couple of weeks ago but the opposite. I was shooting well when the sun was bright. As soon as the light condition changed, I had to fiddle with the knobs. And that makes it worse....

I am using a Premier Reticle 20x50x50mm and the same thing happens at 20x or 50x magnification. I tried cranking it down to 20x and still can't see the target unless canted.

Of cos I could reset myself, reposition the rifle and it'll work but I can't figure out why light would affect it so much.

Any help grately appreciated.
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  #2  
Old 12-08-2003, 06:22 PM
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Join Date: May 2001
Posts: 2,369
Re: POA/POI and focal plane problems

I'm a little confused but the description(s) but I'll offer something.

When you mention you discovered the rifle was canted and you straightened it up the image went "out of the focal plane" (I read as "the image went away, as in disappeared"). Rotating the rifle to remove the cant and having the image "go away" sounds like an astigmatism abberation thing... I'm not a rocket scientist not optical engineer so this is a stab-in-the-dark. You can do a search in the web for astigmatism abberation riflescope or some such and find more info. "Sun up" and "sun down" are often discussed in long range shooting... sun up--- bullet up, sun down---bullet down as I recall... could be garbage but more stuff to look up.

Maybe some optics fella(s) will chime in. Call the folks at Premier and chat with them if they have a few minutes...
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  #3  
Old 12-08-2003, 06:38 PM
Junior Member
 
Join Date: Dec 2003
Location: NZ
Posts: 13
Re: POA/POI and focal plane problems

Dave, how did you know I had astigmatism!!??

Yes, I wear contact lens and I have very high astigmatism. When I try to straighten the rifle the target is gone! Gone I mean outside what I could see in the scope, and I have to move my scope around to find the target again. But this happens when the light condition or something change. Maybe my eye ball moved [img]images/icons/tongue.gif[/img]

But say like I am shooting 4, 5, 6 targets and I remain in the same spot same target same everything, and the light condition change, suddenly, I am missing the target on 7, 8, and 9.

The targets don't just disappear but by missing I meant I open my bolt, recock my rifle and I see the target but I won't hit it dead center. I would be on the white or something.

I look at my rifle's bubble and its canted. So I straighten my rifle but the target is no longer in the scope. To get the target back into the scope, I would have to re-set myself all over. Maybe move the bipod etc.

Whats going on here? help anyone?

Thanks.
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