I don't know how the FRONT Eagle Eyes are working. Are they placed in front of or behind the front aperture and HOW far behind or in front?

The rear lens diopters appear to be functioning much like reading glasses, allowing one to see the front aperture in focus. I would guess they would be nominally about +.5 to +2 diopter or so.

Do you have link that better describes how the front eagle eyes work? Detailed pictures would be helpful.

 

Dear MGT

I have a sight extension tube with adjustable foresight for 50 and 100mts and this has provision for 22mm element inserts all as normal. It is also threaded at the front for an 18mm accessory ( I originally assumed this was for an antiglare tube) but then after looking at this site:-

http://www.intershoot.co.uk/index.html - foresights/eagle eyes

I thought I would run down the path outlined in my first post - assuming the eagle eye in front of the foresight element would enable me to see both target and foresight ring in focus - an ignorant delusion?

If it would work the alternatives seem to be +1.3 or +1.5 diopters - any comments/advice?

Thanks IA
John

 

Dear MGT

http://www.intershoot.co.uk/index.html - foresights/eagle eyes

This links has nothing about eagle eye front sight that I can see. There is something called "eagle eye" score gauge. PLEASE provide direct link to eagle eye description next time.

I have no comments, until a have some detailed pictures of setup.

 

In true compitition you can have an optical aid in either the rear or the front but not both. The rear optical unit is to basically allow you to take off your prescription glasses and dial in your effective Rx to get the front sight in focus.

The front diopter (eagle eye) goes ahead of the front iris so that the target appears magnified in front of the front iris. You therefore need a front iris opening 1.3 or 1.5 times what you had without.

If you have any astigmatism like I do, the rear unit cannot replace your glasses. therefore I have a pair of shooting glasses based on my distance vision but adding .625 diopter so to bring my at rest far focus up to 60 inches. This is inside the hyper focal distance of the sight radius of my match gun (32 inches). I also use a 1.5X (.5 diopter) front lens in 22 mm along with a lens shade. By using these new single focus shooting glases rather than my progressive glasses, it has allowed a wider latitude of head position but still maintain focus on the front sight. It dropped my target confusion so my group size has now gone down by 30%.

HTH clearing up what each is use for. I have had to learn this all the hard way because I have yet to see a real write up on this topic

David

 

In true compitition you can have an optical aid in either the rear or the front but not both. The rear optical unit is to basically allow you to take off your prescription glasses and dial in your effective Rx to get the front sight in focus.

The front diopter (eagle eye) goes ahead of the front iris so that the target appears magnified in front of the front iris. You therefore need a front iris opening 1.3 or 1.5 times what you had without.

If you have any astigmatism like I do, the rear unit cannot replace your glasses. therefore I have a pair of shooting glasses based on my distance vision but adding .625 diopter so to bring my at rest far focus up to 60 inches. This is inside the hyper focal distance of the sight radius of my match gun (32 inches). I also use a 1.5X (.5 diopter) front lens in 22 mm along with a lens shade. By using these new single focus shooting glases rather than my progressive glasses, it has allowed a wider latitude of head position but still maintain focus on the front sight. It dropped my target confusion so my group size has now gone down by 30%.

HTH clearing up what each is use for. I have had to learn this all the hard way because I have yet to see a real write up on this topic

David

As of yet I have not seen anyone post a picture of the front eagle eye lens on a gun.

When you say " I also use a 1.5X (.5 diopter) front lens in 22 mm along with a lens shade." ... I am trying to picture EXACTLY where it is located, and relative to the other parts of the gun (front sight, rear sight, and your eyeball). Also do you mean +0.5 diopter or -0.5 diopter?

You say it is in front of front iris? Do you mean in front of rear sight, that is a peep sight (iris = adjustable aperture)? Or does your front sight have a tiny hole in it that you are calling an iris? An iris in optics is a aperture hole that can be opened or closed, like the iris of your eyeball, so you might be using the wrong word. An iris is also used in camera lens to control the amount of light getting to the film/sensor.

David, sadly all your effort in your words has left me puzzled, and I don't want to second guess. I suggest no more words for now until after posting some pictures of this setup? I can then ask more detailed questions after I see picture.

 

I think the bottom line on diopters is that if your near sighted a front sight diopter is what you need. If far sighted - a rear sight diopter.

T

 

Interesting responses - thanks all.

There does seem to be some confusion (at least I am confused) and this thread is helping me along the way.

The Intershoot link is as follows:-

http://www.intershoot.co.uk/acatalog/Eagle_Eyes.html

and I will try and photo my proposed set-up
Regards
John

 

That is a picture of my Centra front diopter. The centra and the Eagle Eye from OK Weber allow you to screw a Centra front lens shade into it to keep out reflections. This is all screwed into the front (muzzle) end of the globe. then the iris or insert goes behind this lens towards the breech. I will get some pictures soon, mine is dissassembled right now.

David

 

OK, here is a picture of the complete unit. The part with Centra is the sunshade. The knurl to the right of the words is the eagle eye, then the globe body, then finaly the Gehmann fron iris

Here is the sunshade screwed off with the back of the eaggle eye

Hope a picture is worth a thousand words ;-))

David

 

Thank you! Here come the questions..... Answer if you have the time.

What is distance from front lens to aperture/sights? There is no ruler in picture so I don't know scale, and your pictures do not indicate exact position of aperture inside tube.

Can you take a picture inside tube from both ends to show aperture?
What are the numbers on the dial to right? What EXACTLY does the "4" mean, and what does each of the marks mean?

How big is the diameter of the lens? I think I saw 22mm diameter posted somewhere.

Is there any other optics/glass inside the tube, other than the attached/screwed in lens?

What EXACTLY do you see, when using rifle without the lens?
What EXACTLY do you see, when using rifle WITH lens? Details, like wearing glasses and without. Any perceived change in magnification or focus of target? A camera, positioned at normal cheek/eye position at stock, and focused on front sights might be useful, WHILE looking at say a 50 yard target, with and without lens.

One of the posters claims his lens is .5 Diopter, but he never said if it was +.5 diopter or -.5 Diopter. I would like someone to measure this if they have time.

A +.5 diopter lens is a positive lens, with a focal length, in meters, which is defined as the inverse of the diopter. This means focal length is 2 meters if +.5 diopter. A positive lens can focus/create a real image, a negative diopter lens CAN NOT focus a real image by itself.

Keep in mind that this will not work for NEGATIVE lens. The best way to estimate focal length for a POSITIVE lens is as follows:

1. while standing in darken room, point lens out brightly lighted window.
2. Take white paper, and position about 2 meters from rear of lens.
3. If room is dark enough, and outside bright enough, a faint image will come into focus. Sometimes using a paper shade (card board with hole cut in it) is helpfull, to create a dark enough background to see faint image.
4. Distance that an image near infinity comes into focus is called the focal length. Measure/estimate distance from lens to image on paper.

Sometimes I will use the Sun as bright source, and focus sun image onto ground (or something that will not burn) outside, as an estimate of focal length. Keep in mind dangers of looking directly at the sun, even with unaided eyes.

Sometimes I will use a BRIGHT indoor light bulb as source, but in that case the measured focal length is for the distance to light bulb, not infinity, but for short focal length optics, it is sometimes accurate enough. Using the lens formula will always give you focal length at infinity.

There are crude tricks to estimate focal length for NEGATIVE lens if you don't have a known set of measured POSITIVE lens to use. I call it the pencil trick and it usually requires two people. I will post instructions, assuming I can find them, only if you determine this is not a positive lens.

I believe I understand what is happening here, but will hold my explanation until after someone measures the diopter value and confirms that there are no other optics inside.

 

More sophisticated - but Davids set-up is pretty much what I was envisaging. What do you have in your rear sight David?

Questions for responders:-

1. What function does each of the units do - including rear sight parts?

2. What is the product of the whole?

3. I have seen 'diopter. used to describe a measurement/single hole instrument/adjustable hole instrument/dual lens instrument!!! What is a diopter - and why expressed as +/- .5 or 1.5?

4. What are hyper focal distance/single focus/ progressive focus?

5. What is a Galilean sight?

6. Not that it will affect me, but finally - it seems International/American/UK target shooting rules probably differ in the legal use of the foregoing instruments - are there any fairly straightforward rules?


I realise this is repetitive/a bit like 'painting by numbers' and I am stretching the patience of responders - but hope you will bear with me ---

TIA

John

I see this crosses with MGT's latest

 

Diopter

John,

The maker of your "small" diopter (unmarked) may well be Redfield. Is there a silver serrated sleeve and uncommon threads?

bjm

 

Battery awaited for camera - so will try and post details of my diopter on monday
John

 

Great stuff.

Very interesting, always humbling experiences waiting here, hoping to learn.

Thanks all.

 

MGT,

Here are responses to your questions

What is distance from front lens to aperture/sights?

The globe body itself is about 1.5 inches long.

Can you take a picture inside tube from both ends to show aperture?

Yes but all you see is the main iris that looks like a black donut. Unless far away the apparent magnification of the lens is not evident.

What are the numbers on the dial to right?

This iris goes from 4 mm to 6 mm. The 6 is in the glare of the flash. Each mark is .1 mm

How big is the diameter of the lens?

Yes it is a 22mm They come in either 18 mm or 22 mm. the advantage of 22mm is you get to see more of the target, like the number boards easier.

Is there any other optics/glass inside the tube, other than the attached/screwed in lens?

No, none other is allowed

What EXACTLY do you see, when using rifle without the lens?

same as with the lens but the target is less magnified so you have to use a smaller settingon the iris.

What EXACTLY do you see, when using rifle WITH lens?

The target black is 1.5 times larger than it would be without the lens. The black iris is supperimposed on the target. Since all is magnified, this gives you a more critical centering and beeter control.

Details, like wearing glasses and without.

Since I cannot see much of anything without glasses that is a moot point.

Any perceived change in magnification or focus of target?

Yes 1.5X for a .5 diopter and 1.3X for a .3 diopter.

A camera, positioned at normal cheek/eye position at stock, and focused on front sights might be useful, WHILE looking at say a 50 yard target, with and without lens.

Can't do that one easily, sorry

One of the posters claims his lens is .5 Diopter, but he never said if it was +.5 diopter or -.5 Diopter. I would like someone to measure this if they have time.


I am almost 100% certain it is +0.5 diopter. It does sort of focus an image but I have not tried it on a point source to get a true reading. It is sort of like having your reading glasses way far out. The peep gives you fine position adjust ment as well as depth of field.

HTH

David

 

MGT,

Any perceived change in magnification or focus of target?

Yes 1.5X for a .5 diopter and 1.3X for a .3 diopter.

Did you actually measure the 1.5X magnification and 1.3X magnification or are you quoting some advertisement or spec by company. If you measured it yourself, then HOW did you measure it, and what is your estimated measuring error?

 

GNR527,

Here are your answers:

1. What function does each of the units do - including rear sight parts?

The rear serves a fine position control. The smaller the aperature the finer the control but the less light and harder to see. You use it as a base to then center the front donut iris around the black center. You generally want the iris to subtend 2X the black so the white sepeartes the black iris and the black bull. When you have equal white on all sides and the peep hole is centered around the front globe you are true and a bullet fired would go through the X ring if you are perfectly calibrated for hat ammo and distance.

2. What is the product of the whole?


See 1 above

3. I have seen 'diopter. used to describe a measurement/single hole instrument/adjustable hole instrument/dual lens instrument!!! What is a diopter - and why expressed as +/- .5 or 1.5?

Unfortuanately people have called the irises of the peep sight and the front donut, diopters. That is FLAT wrong. they are irises, no more. the lens has a diopter strength. 1 diopter is 1 meter of focal distance. . diopter is 2 meter. Your lens prescription for glasses is expressedin diopters


4. What are hyper focal distance/single focus/ progressive focus?

hyper focal dstance is a value that when a lens if focused at all apears sharp ffrom 1/2 that distance to infinity. Progressive lenses are glasses that are continous focus from near to far. Another name is linesless trifocals Think old age here ;-))

5. What is a Galilean sight?

That is a simple telescope of a single front lens with long focal length coupled with a single lens of shorter focal length. The magnification is the value of the longer divided byt the shorter.

6. Not that it will affect me, but finally - it seems International/American/UK target shooting rules probably differ in the legal use of the foregoing instruments - are there any fairly straightforward rules?

No clue on this one. I only know about CMP and NRA small bore and I am allowed the one lens in the front or one lens in the rear but not both.

HTH

David

 

MGT - fantastic - many thanks.

Off to shoot .

Will come back tomorrow

John

 

For all who want to use an aperature front sight. Here is an excellent article on it:

http://www.triplej.com.au/pdfpages/Aperture.pdf

From the first oage here is how the sight should look like. The eagle eye doesn't change anything except the target gets magnified.

Hope that helps clear up the picture ;-))

David

 

Excellent illustration.:bthumb:

 

David - excellent article - thanks

Brian - I think you are right in that my diopter might be a Redfield - i'll try and post pics:-

http://i404.photobucket.com/albums/pp126/Palmeirajw/REDFIELDVARDAD2.jpg

http://i404.photobucket.com/albums/pp126/Palmeirajw/RedfieldVARD3.jpg

http://i404.photobucket.com/albums/pp126/Palmeirajw/RedfieldVARD2.jpg

http://i404.photobucket.com/albums/pp126/Palmeirajw/RedfieldVARD1.jpg

I think the bit I have is just the diopter, not the iris, filters etc

I hope the pics are not too big

Regards
John

 

I think what you have is a eye sight correction unit that allows you to adjust the focus of your eye for the front sight wihtout using glasses. Do you twist the knurled barrel and that chaanges the sight picture from fuzzy through sharp to fuzzy again?

David

BTW, if you had used the last line /img....img/ on photobucket it would have put the pictures in this post automagically

 

David

Yes it does - doesn't half make life easier.

and thanks for the advice on pictures.

I must say this thread has been most informative

John