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hasbo View Drop Down
Optics GrassHopper
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hasbo Quote  Post ReplyReply Direct Link To This Post Topic: Hi - new to the forum with a question
    Posted: July/07/2021 at 15:38
I measure the eye relief by shining a light through the objective and seeing how far away from a surface the smallest exit pupil is :-


[The peripheral ring of light is stray light .]

Too close to the ocular and I can see an image of the reticle :-




Too far out and I can see an image but it is INVERTED (and reversed) :-



The only problem is - no matter how I try or what I do, I can't get this effect when I look through the scope.

[it happens for sunlight as well as torchlight - the same effect whether 1st or 2nd focal plane. ]

{sorry about the picture quality - it is usually much better - but can anyone explain this ??}
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Optics Master Extraordinaire
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scrumbag Quote  Post ReplyReply Direct Link To This Post Posted: July/08/2021 at 08:41
So what's your issue? Is the image upside down when you look through the scope?

Might be worth just fitting the scope so it works with your eye...

Welcome on board from London!
Was sure I had a point when I started this post...
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hasbo View Drop Down
Optics GrassHopper
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hasbo Quote  Post ReplyReply Direct Link To This Post Posted: July/08/2021 at 13:34
I know full well that the scope works for my eye in practice (it was previously fitted to a rifle).
[This one was chosen as it had a vertically asymmetrical reticle  so the inversion could be see.]

My problem is, it is something I don't understand and I would like to.

I posted the same thing on another forum (NOT Optics specific) and had this response :-

"I guess that makes sense - 'focuses' at the point the exit pupil appears smallest and then the 'rays' continue and cross over inverting the image...."

To which I replied :-

"Yes - BUT - I can see it as a projected image (clearly inverted) but with my eye in the same position as the screen it isn't inverted.
Try it with any scope you like, but it has to be a vertically asymmetric reticle or you can't tell the difference. ðŸ˜‰"

To which he replied :-

"That's weird😨😱"

And I said :-

"Ain't it just. "
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hasbo View Drop Down
Optics GrassHopper
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hasbo Quote  Post ReplyReply Direct Link To This Post Posted: July/09/2021 at 14:21
Problem solved, I now know the reason and my curiosity is satisfied. Wink 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Urimaginaryfrnd Quote  Post ReplyReply Direct Link To This Post Posted: July/09/2021 at 19:52
WHY...........Get Your Popcorn Ready

"Always do the right thing, just because it is the right thing to do".
Bobby Paul Doherty
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hasbo View Drop Down
Optics GrassHopper
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hasbo Quote  Post ReplyReply Direct Link To This Post Posted: July/10/2021 at 03:06
One is the "real" image of the reticle - the other is the "virtual" image. Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Son of Ed Quote  Post ReplyReply Direct Link To This Post Posted: July/10/2021 at 06:20
Actually, I'd rather hear about Nottingham....   Smile
Visit the Ed Show
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hasbo View Drop Down
Optics GrassHopper
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hasbo Quote  Post ReplyReply Direct Link To This Post Posted: July/10/2021 at 08:28
My apologies - I misinterpreted the nature of this forum, the name is a little misleading. Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Urimaginaryfrnd Quote  Post ReplyReply Direct Link To This Post Posted: July/10/2021 at 13:19
Tell us about Nottingham.  The forum offers many different things but for me I am more into practical applications of optics particularly tactical optics.  Koshkin is well educated in Optical Physics so perhaps he would have more insight into technical questions.  And we would love to hear how things are in Nottingham. 

"Always do the right thing, just because it is the right thing to do".
Bobby Paul Doherty
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Kickboxer Quote  Post ReplyReply Direct Link To This Post Posted: July/10/2021 at 14:56
Many addressements of this question on Youtube... didn't see the need to go over it again.
Opinion,untempered by fact,is ignorance.

There are some who do not fear death... for they are more afraid of not really living
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