TargetTalk

A forum to talk about Olympic style shooting, rifle or pistol, 10 meters to 50 meters, and whatever is in between. Hosted by Pilkguns.com
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 Post subject: Optical puzzle
PostPosted: Mon Jan 09, 2017 5:04 pm 
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Joined: Wed Dec 17, 2014 4:26 am
Posts: 105
Optical distortion line running through middle of rifle sight picture.

Checked rear sight, but as it has no optics, I cannot see a problem or obstruction
Checked iris, and as it is a plain iris, it is just an opening. no optics. Made sure it was clear, no obstruction.
Checked front sight. has Anschütz pink insert, clean and undamaged
Check my shooting lens rotation orientation. Turned it 180 degrees with no change.

The problem is a focus aberration that runs right through the middle if the sight picture. As I move the sight I can see a change in focus between the top and bottom halves of the sight picture, particularly at the cnter orifice. Plays hell with trying to maintain front sight focus.

I have tried different front sight inserts and three different iris discs, all manifest the same aberration. So I have come to the conclusion that the problem may very well be with my eye and not the front rear sight combination. As a final test I changed shooting eyes (left instead of right) and the problem is gone. Any sports opticians/opthamologists want to share their thoughts?


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 Post subject: Re: Optical puzzle
PostPosted: Mon Jan 09, 2017 6:43 pm 
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Joined: Sun Sep 04, 2016 10:59 am
Posts: 343
Location: A new global Great Britain
This is easy for me to say as being over 60 I get free eye examinations in my country, but I would book an eye exam pronto and have the eye checked out. Hopefully its a temporary foreign body on the cornea and simple dry-eye drops (artificial tears) may help.


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 Post subject: Re: Optical puzzle
PostPosted: Wed Jan 11, 2017 6:06 pm 
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Joined: Sun Dec 12, 2010 1:50 pm
Posts: 407
Location: San Diego, CA
Yep, I second that suggestion. Sounds like you've pretty well isolated it to your right eye, so, assuming it's a recurring problem, probably worth paying a visit to your eye doc.


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 Post subject: Re: Optical puzzle
PostPosted: Thu Jan 12, 2017 2:35 pm 
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Joined: Wed Dec 17, 2014 4:26 am
Posts: 105
Update!

Well, had my exam today. Generally I have reasonable vision, as below:

Right Spher. 0. Cyl. .5. - 120
Left Spher.+1.0 Cyl. 0

However, the right eye has the befinnings of a very small, posterior cataract, which unfortunately is located precisely in the center of the lens. My opthamologists opinion is that as my vision is for the most part very good for general vision, he would be inwilling to perform cataract surgery just to accommodate my shooting hobby. I tend to agree with him.

So what are my options?

1. Ignore the artifact and just learn to deal with it.
2. Shoot right handed, aim with left eye
3. Change everything over for left handed/left eye shooting

Has anyone used options 2 and 3?

Regards Paul


Last edited by Pheyden on Fri Jan 13, 2017 2:34 am, edited 1 time in total.

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 Post subject: Re: Optical puzzle
PostPosted: Thu Jan 12, 2017 3:27 pm 
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Joined: Sun Sep 04, 2016 10:59 am
Posts: 343
Location: A new global Great Britain
if you're still hitting the target I would go with 1. And an annual eye check.


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 Post subject: Re: Optical puzzle
PostPosted: Fri Jan 13, 2017 5:24 am 
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Joined: Fri Sep 17, 2010 5:32 am
Posts: 385
Location: London, England
Bad luck. I sometimes have a feeling something similar is happening with me (eye exam imminent).
I'd go with option 1 but investigate option 2.
A crossover sight or offsets are a lot cheaper and easier than changing your whole setup and relearning your technique.
Not a perfect solution but...

Regards.
K.


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 Post subject: Re: Optical puzzle
PostPosted: Sat Jan 14, 2017 10:26 am 
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Joined: Wed Dec 17, 2014 4:26 am
Posts: 105
Had another chat with my eye doctor and formthe moment we are going to try #1. I am having Neal at ISS make a couple if new lenses for both rifle and pistol, and I will see how I go. I have taken the position that it is not the end of the world and good things may result from all this.


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 Post subject: Re: Optical puzzle
PostPosted: Tue Jan 17, 2017 3:03 am 
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Joined: Tue Sep 27, 2016 5:00 am
Posts: 1
Location: Melbourne, Australia
This might seem an obvious explanation but worth putting forward - I experienced something similar at times while I was using my Champion glasses and found that it was the alignment of the lens around the aperture and placing the rim of the lens across the sight picture. Adjusting the alignment was not easy because of the position of the lens being so close to the nose piece. I now use the Ahg lens holder fixed to the rear sight and no further problems.


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 Post subject: Re: Optical puzzle
PostPosted: Tue Jan 17, 2017 7:46 am 
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Joined: Wed Dec 17, 2014 4:26 am
Posts: 105
Markrem, thanks for the suggestion. I am already using the MEC Monocle system mounted on my Anschütz rear sight. This assures that I am looking through the centre of the lens. Still, this anomaly was there. I have been playing around with a variable opening size in the iris. When I use a larger iris size (1.2instead of .8mm), I can "tune out" some of the effect due to changing the overall depth of field. I was given this idea by Neal Stepp in the USA, and it seems to work. He also indicated that due to varying light intensities at different ranges, it is vital to use an iris that can be varied in size. Neal is mqking me some new shooting lenses, so we will see how these work with a variable iris.


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 Post subject: Re: Optical puzzle
PostPosted: Tue Jan 17, 2017 7:58 am 
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Joined: Sun Sep 04, 2016 10:59 am
Posts: 343
Location: A new global Great Britain
I have noticed in rifle and pistol ( when I experimented with a knoblich iris) that too small an iris aperture will magnify any eye defects. I have no idea why but it happens even if its a stray eyelash. on rifle a 2mm iris makes little difference to accuracy at my level compared to 1.1mm.
0.8 will be severe in this regard.


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 Post subject: Re: Optical puzzle
PostPosted: Wed Jan 18, 2017 11:10 am 
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Joined: Wed Dec 17, 2014 4:26 am
Posts: 105
TenMetrePeter - I concur that very small iris apertures can have this effect. I have switched over to an iris with a variable aperture and am playing around with larger sizes. Will see how I go over the next few weeks.


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