Disassembly and Collimating Nikon 7x35 9.3°? (1 Viewer)

[henry link]

I just happen to have a friend's pair of these old Action 7x35s in my house right now. It needs some fungus removed.

The photo below shows the left eyepiece partly disassembled. You just unscrew the cowling with the rubber eyecup on it and then pry and slide out the goop covered cylinder that holds the optics.

 

[Red_Shoulder]

I just happen to have a friend's pair of these old Action 7x35s in my house right now. It needs some fungus removed.

The photo below shows the left eyepiece partly disassembled. You just unscrew the cowling with the rubber eyecup on it and then pry and slide out the goop covered cylinder that holds the optics.

Thanks! Is the right the same way? I looked at that the other day and thought it was the hard way in. Pulled it out, have to look at it and see if it might be possible to replace an element

 

[Red_Shoulder]

I was going to suggest that much earlier, but didn't want to interfere.
Swapping objectives sometimes works.

I have seen eyepieces so badly scratched as to render top binoculars useless.

Thanks! These are still useful, but if the bird is on a branch against clouds, i.e. high flare, they're not so easy to see birds with. But if it's fairly evenly lit, they're not bad.
Not sure how these get so bad, any idea? Is there any solution for the ones you've seen?

 

[Binastro]

Yes, wiping the eyepieces repeatedly on a sandy beach with an old hanky.
Often the right eyepiece is worse than the left.

Good makers stock eyelenses and replace them regularly.

The eyelens is often harder glass and sometimes flat surfaced.

P.S.
With the value of the Nikon mentioned it is not economical to repair unless you find an identical scrap binocular.
You would need to find a piece of glass with correct curves and correct glass type from Surplus Shed. This is unlikely. Also similar coatings and correct thickness.

 

[Red_Shoulder]

Yes, wiping the eyepieces repeatedly on a sandy beach with an old hanky.
Often the right eyepiece is worse than the left.

Good makers stock eyelenses and replace them regularly.

The eyelens is often harder glass and sometimes flat surfaced.

P.S.
With the value of the Nikon mentioned it is not economical to repair unless you find an identical scrap binocular.
You would need to find a piece of glass with correct curves and correct glass type from Surplus Shed. This is unlikely. Also similar coatings and correct thickness.

Binoculars are just telescopes, and I change eps all the time on those, so it might not be that picky.

Im going to take a look in a box of optics I got, I think to make eps for telescopes, and see what happens. I haven't tested objective focal length yet, need to do that. Might look at surplus shed diy eps.

Anyone know how to remove the right? I hate to crank too hard , not knowing what I'm doing.

 

[Binastro]

Hi Red Shoulder,
Changing a whole eyepiece may be easier than replacing an element.

However, modern WA Nikons like that have aspheric elements, which you won't find normally on an astro eyepiece.
You could easily find a near correct focal length, but I don't know if you would like the resulting view from a different eyepiece.

A 35mm objective might be 140mm fl, so 20mm eyepiece 65 deg. Erfle, but a modern Nikon aspheric might be 4 element not 5? Maybe your Nikon uses spherical surfaces.

 

[Binastro]

You might be better off changing both eyepieces for a matching pair.

18.5mm eyepieces might be more likely?

You could put in shorter focal length eyepieces and get a higher magnification. The prisms would be a bit oversize then maybe, but less vignetting.

 

[Red_Shoulder]

Yeah, it would be easier to just drop in a new ep, but I'm not sure if I can find 2. Definitely interested if available.

I think it's probably spherical, given the age and cost new?

Concerned about the view, but itshould have higher contrast, which it needs. I think it will be ok, hope so.

I got the ep open! The diameter is 0.745 in. (18.9mm.) Focal length is about 39-45mm, if it's 35mm, my estimates get about 7.5x. 2 plano-convex and 1 achromatic doublet, imo.

 

[Binastro]

I don't think so.

If the field lens is 17mm diameter and the focal length 39mm. Then the AFOV is about 25 deg.
This is not so, as the AFOV is about 65 deg.

You might get a pair of eyepieces from a scrap binocular.

If you have one very dominant eye, maybe any eyepiece will do?

At least it will be educational if you continue with the binocular.

 

[Red_Shoulder]

Yes, the element closest to the eye is a little less than 19mm and I measured the focal length more than once, it was about 39-45 mm.

The ones available at this diameter were similar focal length. Doubt this is anything too rare.

I doubt there is much chance of finding a scrap binocular, but I'd be interested if available.

 

[WJC]

Hi Red Shoulder,
Changing a whole eyepiece may be easier than replacing an element.

However, modern WA Nikons like that have aspheric elements, which you won't find normally on an astro eyepiece.
You could easily find a near correct focal length, but I don't know if you would like the resulting view from a different eyepiece.

A 35mm objective might be 140mm fl, so 20mm eyepiece 65 deg. Erfle, but a modern Nikon aspheric might be 4 element not 5? Maybe your Nikon uses spherical surfaces.

And, being a busy-body, I'll tell you that many of those aspheres are made by Bob Mathews at Mathews Optical Works in Poulsbo, Washington.

Bill

 

[OPTIC_NUT]

If you are talking about the Aculon 7x35//9.3,
the aspherical element is quite likely the field lens.
So...an aspherical PCX with nearly the same fl could replace that..
...if you get lucky with diameter.

Then you would have the nightmare of another EP that isn't parfocal.

I have some nice glass asphericals field lenses but they are from 7x50s (a bit wide).
They making shockingly good magnifiers... clean at 4x when a spherical the same fl
will only give me 2.5x

 

[Binastro]

Hi Red Shoulder.
The field lens is the element furthest from the eye.
What is the clear aperture of that?

Measure the focal length of the objective and divide by 7. That will give you the fl of the eyepiece approx. It is likely the magnification will change slightly at the edges, but we can forget that.

39 to 45mm is not the eyepiece fl.

The Nikon Action VII has aspheric eyepieces and the magnification varies slightly across the field.
The aspherics maybe a plastic on glass sandwich or just glass?

Zeiss had a mechanical aspheriser in the 1930s, but not their invention.

Here charity shops are full of faulty binoculars for a fiver. You could find box loads.
It is lucky when you find a good one, and occasionally gems for very little money.

In Sweden they have those Visby aspherical magnifiers made about the year 1,000.

P.S.
Red Shoulder.
Did you take the eyelens out and are you saying that is 39 to 45mm focal length?
If so, I apologise.
I thought you were quoting the whole eyepiece focal length.

P.P.S.
I think what you are saying is that the element nearest the eye is 18.9mm diameter and is an achromatic doublet of 42mm +/- 3mm focal length.
If this is correct.
Then one still has to find a doublet of the correct thickness. If lucky it might work.
And that the eyepiece is 4 elements.
I don't know when the Nikon Actions started using aspheric eyepieces.

 

[Binastro]

Re. last post 33.

If what I thought is correct, then changing both eyelens doublets for the nearest match you can find might work.
But they would need to be centred carefully and not tilted.

The other approach would be to find similar broken 7x35s. Nikon, Pentax, Olympus eyepieces might work.

 

[Red_Shoulder]

Yes, just the element closest to the eye is 39-45mm focal length, that's ok. The others are 50-55mm and 67mm (hard to measure these exactly) .

So I plugged all 3 in to get 17.3mm-20.9mm or so for the whole thing, depending on how far apart the elements are.

I still need to measure the objective's focal length, but 7x at around 20mm would be 125-150mm range, like you'd expect.

Based on another thread, these seem to be mid 80's or so, $80 new. Afaik, aspherical lenses were not common in more-expensive camera lenses at this time, so I wouldn't expect them here. Also, the diy ep I got off ebay (erfle) gives nice performance at about 60°, and I don't think it was aspherical at $13. So hopefully, for the repair at least, the element isn't aspherical.

But if it is, I might contact Mathews Optical and see if they'll sell me a few, or if they generally sell 1000+ at a time.

 

[Binastro]

Yes, the separations are maybe critical.
Probably 5 element Erfle, all spherical.
Objective fl probably 120 to 130mm.

7x35, 8x40 and 10x50 probably same eyepieces, even same bodies.

Erfle maybe little eye relief.

Russian Erfles from 8x30s are very nice, Zeiss copies. 15.5mm approx. little eye relief.

Let us know how you get on with Erfle swop.

Entertaining, although I would have let them be at my age.

 

[WJC]

Yes, just the element closest to the eye is 39-45mm focal length, that's ok. The others are 50-55mm and 67mm (hard to measure these exactly) .

So I plugged all 3 in to get 17.3mm-20.9mm or so for the whole thing, depending on how far apart the elements are.

I still need to measure the objective's focal length, but 7x at around 20mm would be 125-150mm range, like you'd expect.

Based on another thread, these seem to be mid 80's or so, $80 new. Afaik, aspherical lenses were not common in more-expensive camera lenses at this time, so I wouldn't expect them here. Also, the diy ep I got off ebay (erfle) gives nice performance at about 60°, and I don't think it was aspherical at $13. So hopefully, for the repair at least, the element isn't aspherical.

But if it is, I might contact Mathews Optical and see if they'll sell me a few, or if they generally sell 1000+ at a time.

Please don't bother, I would like to keep Bob as a friend; he doesn't do one-off projects. By the same token, if you want 10,000, go ahead a give him a call. Maybe, I can get some burger money out of the deal. And, like everything else in optics, one size does not fit all. If he is making aspheres for a given bino, chances are that is the only Nikon contract he has at the time—although next month may be different. :cat:

Bill

 

[Red_Shoulder]

Yes, the separations are maybe critical.
Probably 5 element Erfle, all spherical.
Objective fl probably 120 to 130mm.

7x35, 8x40 and 10x50 probably same eyepieces, even same bodies.

Erfle maybe little eye relief.

Russian Erfles from 8x30s are very nice, Zeiss copies. 15.5mm approx. little eye relief.

Let us know how you get on with Erfle swop.

Entertaining, although I would have let them be at my age.

The 32mm Erfle works fine in a telescope, I should have pointed out I'm not using in binoculars. It would be difficult to get it to fit binoculars.

The Erfle is 5 elements; 2 achromats and a double convex. The 9.3° 7x35's take a 4 element: 2 Plano convex and an achromatic doublet.

 

[Binastro]

I think I had a 32mm Erfle in 2 inch fit.

$13 is really cheap.

I have a 20mm Erfle in 1.25 inch fit.

Also the Russian 15.5mm Erfle or Bertele? fits 0.965 inch or 24.5mm fit. (Sold as E59 in the U.K.)

 

[Red_Shoulder]

Yes, my 32mm is a 2". Just sent the elements, and you have to figure out what to put them in.

The field stop on the 9.3° ep is about 24.5mm.