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NM sight question

1508 Views 6 Replies 5 Participants Last post by  ShootingSight
I am now old (63.9+), nearsighted, and can not "easily" focus on the rear, front and targets like I could, oh, about 25 - 30 years ago when I shot competitively, and actually won (GI3) from time to time! Imagine that, huh?

Anyhow, the other day I was looking through my SAI's NM sights, the one with the 180˚ rotatable peep sight, and I thought perhaps there was something (Lint? Oil? A small mouse?) in the way, so I cleaned it out and still, when I looked in there, I saw the same problem.

It appears to me to be a group of three small circles, each the size of the actual bored peep hole, but located in a nice neat triangle, with the one true peep hole at the top and the other two placed equilaterally to the sides, but dropped down in a triangular formation and overlapping the top circle. It seems as though the other two are a reflection of the major hole, reflected off the inner sides of the peep sight tube.

This makes it a bit more of an ewffort to first-off ID which is the correct hole to use in order to pick off the 6" target circle @ 600 yds (GI3... Just kidding. I can only do that @ 200 yds... GI2)

Has anyone else ever noticed this anomaly, or reflection issue? If it is a reflection, I may have to spray the inner tube with some DuraCoat in ultra-flat black, or perhaps line the tube with a tiny little tube of black emory paper?

Or perhaps it's Mine Eyes not Seeing The Glory any more, but instead focusing more readily on some visual anomaly of my own making.

PS: it's gettin' cold up here in wonderland! Maybe it's jist me eyes shiverin'?
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· "Death From Above"
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12,457 Posts
Dont feel bad I am 47, I go to the doc and he tells me I passed with 20/10 near and far vision. I ask him to explain why In the last year I am moving my Iphone further away in order to read it. I went to the VA and got my eyes checked and the hotty young eye doc tells me I need reading glasses, the lowest they make, i think a number 1 or something no pun intended. I am starting to see fuzz like crap in the rear peep sight. I thought there was actually fuzz in there and I cleaned and cleaned and that dam fuzz doesn't go away. I am already using a .595, not many options after that. I feel your pain.
 

· Eye Master
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4,295 Posts
There are a lot of guys out there either selling snake oil, or at least not undersanding the optics of what is going on. Here is the real problem ... and if you skip to the last paragraph, you can just get the answer without all of my pontification.

The relaxed human eye focuses in the distance. You have the cilary muscle in the eye that pulls your focus in close. As you get old, the lens in your eye gets hard, so the cilary muscle is no longer up to the task, and you can't pull your focus up close. The non-shooters among us recognize this as insufficient arm length, too damn dark in a restaurant to read the menu, and sitting on (and crushing) the third pair of reading glasses this month.

Shooting also requires you to focus up (slightly) closer than where your relaxed eye wants to focus. Reading glasses shift your focal point WAY too far up close - even the weakest reading glasses will give you a GREAT front sight, but your target is so far fuzzy, you are lost.

Withoiut making this a 3 page long post that has all the optical math I have worked, the bottom line answer is that to perfectly distribute your depth of field between the front sight and the target, you need your eye to focus at the hyperfocal distance of the front sight. I could tell you how the math works, but bottom line is that for a longer rifle, like an M1 or M14, you want a +0.5 diopter. If you wear glasses for distance vision, you want a +0.5 diopter added to your current prescription.

Yes, there are some eye diseases that require more light, and you have no option but to open the aperture, but these are really rare. Most people just need a +0.5 helping lens, and you can suddenly see like you were 18 again.

Note, the lenses fix your eyes only. Other parts of your body will NOT function like you were 18 again just because you listen to an old fart on the internet.
 

· Registered
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Discussion Starter · #5 ·
Pipe Dreamin'

Shooting also requires you to focus up (slightly) closer than where your relaxed eye wants to focus. Reading glasses shift your focal point WAY too far up close - even the weakest reading glasses will give you a GREAT front sight, but your target is so far fuzzy, you are lost.

...the bottom line answer is that to perfectly distribute your depth of field between the front sight and the target, you need your eye to focus at the hyperfocal distance of the front sight. I could tell you how the math works, but bottom line is that for a longer rifle, like an M1 or M14, you want a +0.5 diopter. If you wear glasses for distance vision, you want a +0.5 diopter added to your current prescription.
I've heard about this hyperfocal distance thing from the guys at DeCot Hi-Wyde, whose optics I'll probably be purchasing. They can do an adjusted Rx set up in the corner near the nose bridge, in my case to the left-side lens, since I'm one of those superior left-handed types (We're actually proven to be smarter you know! Really!).

As well, their glasses have an adjustable-height nose bridge so I can set them up higher for shooting, and then back down for when I cooly drive my "Arrest Me Red" Porsche 930 Turbo Convertible back to the house. You know; soz the cute girlz can OOGLE me you understand, and then I can yell back to them: "Lookie! I got a great aggregate shooting score today! Hdy: Yah wanna do some coffee with Geritol?!"!

http://images.search.yahoo.com/imag...b=136h1fos9&sigi=11p5reu6t&.crumb=VRmhO9y8E43

(Riggghhhttt...)

So... thanks guys so much for the confirmation that I'm not alone here, and for the optical-tech info. Now maybe I can get that 10 shot aggregate 42" score again, with iron sights, out @ 1000 meters, with a Parker-Hale modified .303 Enfield!

(GI3 NBL...)
 

· Registered
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97 Posts
.75 reading glasses

What art7 says!

Had my 60 year old eyes examined several months ago. Dr wrote me a prescription for +.50 reading glasses to use for shooting at my request. After pricing prescription reading glasses (expensive!) I searched the internet and found some $25.00, +.75 reading glasses that I can use as shooting glasses. Made it much more relaxing for my eyes while aiming. I can see the front sight clearly and distance vision is good also.

If I could find a reasonable priced pair of +.50 reading glasses I would buy them. Had tried a pair of +1 power glasses. While I could see the front sight clearly the distance was blurred a little to much. The lower magnification reading glasses seem to be harder to find.
 

· Eye Master
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4,295 Posts
Bonnie,

Take a look at my website - I just started selling +0.5 and +0.75 safety glasses for shooters for $35. I have had the PD moved to the center on these, so the optical center will be somewhere between what you need for offhand, and what you need for prone.

The ones I actually have in stock are the last of my prototype run, and have a slightly different look that is more 'wrap around'. They do not have an adjustable nose piece, and the lenses do not go as far to the center as the Hi-Wyd glasses, but since they are true ANSI Z87+ rated safety glasses, and only cost about 20% of the price of a pair or HiWydes (which are NOT real safety glasses), it's a pretty sweet deal.

Art
 
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