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Binocular focusing range?


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I bought a pair of Opticron Imagic 10x50s recently, and am very surprised to find that they don't accommodate my eyesight.

I have -6.0 dioptre myopia, and the binoculars focus fine up to about 15 metres without glasses, but I can't focus beyond this distance as there is no focus travel left. Wearing glasses, they focus to infinity, but only right at the end of the focus travel. That means anyone with myopia can't use these for astronomy! :hello2:

Is it normal to have such limited focus travel in binos?

Can they be adjusted?

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This is strange. With perfectly corrected vision, all bins I have ever tried had quite some focus travel beyond infinity. Very often this is needed not just to accommodate imperfect vision, but also thermal expansion issues (and most factories cannot be bothered to do the tight quality control required). I cannot really see an easy solution, as the EPs need to travel closer to the objectives. The bins might need to be returned

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Strange. These are popular binoculars, so it's hardly likely that this is normal for this model as there would be plenty of complaints.

I found the focus action to be quite stiff as well, so perhaps that's part of the problem, although I don't know what a normal pair feels like...

Andrew

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Is it normal to have such limited focus travel in binos?
I'm not sure how "normal" it is, but it is certainly not uncommon. For example, the Helios Stellar 15x70 I once had hit the limit at about 1 dipotre of myopia (not a problem for me as I have hypermetropia). The issue is that, to focus for myopia, the binocular needs to focus "beyond infinity" for normal vision.
Can they be adjusted?
That depends -- you will need to contact the importer/manufacturer.
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Hi Andrew,

Whilst your -6 prescription is not extreme, it is unusual. We are not aware of any similar comments from other purchasers.

There are tolerances in focus performance mainly due to the manufacturer trying to meet close focus targets. The Opticron 10x50 Imagic TGA is understandably popular amongst astronomers but is intended to be a general purpose binocular with 4.5 metre close focus.

I have spoken with Pete Gamby at Opticron. He is happy to adjust the binocular to allow for more focus reach 'beyond infinity' to make it more suitable for your needs (mainly astro) but this would make them less desirable to someone wanting to use them for regular use so it would probably seriously dent its resale value.

Please contact me via the the email below if you would like to accept Pete's offer.

HTH,

Steve

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What I did with one recalcitrant pair of 10x50 binoculars was to unscrew one of the eyepieces and move it out slightly. The problem I had was that I could achieve focus for one of my (short sighted) eyes, but the other was outside the range of travel and rotational EP correction.

It means that particular pair are customised for my eyes only but it seemed to work.

While performing the "surgery" I also discovered two small grub screws, covered by that plastic imitation leather on the body - one on each barrel. It turns out these adjust the angle of the prisms in the body. By tweaking these I was able to collimate them to a better degree than they were, new.

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What I did with one recalcitrant pair of 10x50 binoculars was to unscrew one of the eyepieces and move it out slightly. The problem I had was that I could achieve focus for one of my (short sighted) eyes, but the other was outside the range of travel and rotational EP correction.

It means that particular pair are customised for my eyes only but it seemed to work.

While performing the "surgery" I also discovered two small grub screws, covered by that plastic imitation leather on the body - one on each barrel. It turns out these adjust the angle of the prisms in the body. By tweaking these I was able to collimate them to a better degree than they were, new.

Moving out is comparatively easy, but here we need to move in.

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Hi Andrew,

Whilst your -6 prescription is not extreme, it is unusual. We are not aware of any similar comments from other purchasers.

Well this is just the point! The infiinity point with glasses is right at the end of focus travel, suggesting ANY level of myopia would not focus. Clearly this is not a typical example or you would have complaints from every shortsighted customer....

I have owned 5 other pairs of binoculars and no other pair have had this issue - have I been lucky?

I appreciate the offer from Opticron - thanks.

Andrew

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You do know you can return 'any' binocular purchased from us within 30-days, don't you. We can also dispatch a second binocular for you to compare. That and Pete's offer to modify them free of charge means you are sitting pretty.

Don't lose any sleep Andrew, you're covered :hello2:

Steve

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