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Opticron eyepiece assembly.

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Old Thursday 27th December 2018, 18:47   #1
johnphearson
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Opticron eyepiece assembly.

Hi. Im new to this birdforum, To be honest I only joined to ask this question.
Im a novice bird and wildlife watcher. This forum looks very interesting, Im sure I can learn a lot from it.

Ive just bought a pre-used opticron es 80 scope. It came with a zoom lens and a wide angle lens (Opticron 40931 HR2) I took the wide angle lens apart to clean as the fist eye lens was dirty inside, I never expected 4 lenses inside, I think I have it back together Okay but just wondered if anyone had an exploded diagram of it.
Any help?
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Old Thursday 27th December 2018, 19:58   #2
Binastro
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Hi John, welcome.

I have taken many eyepieces apart and cleaned them, but many here wouldn't try.

Firstly, one has to carefully note each element, front and back and position.
If there are spacers that is a problem and they have to be arranged with no possibility of mistakes.

If the lens elements are edge blackened then it is difficult to mark them with pencil on the edge with angled marks.

However, if the eyepiece performs well, it is probably correctly assembled.

Are the 4 lenses single elements or are some cemented doublets?
These give extra reflections from a single light bulb.

So it could be 4 groups with 5 elements, maybe Erfle eyepiece.
If only 4 single elements, likely a Plossl, but not very wide angle.

Opticron can probably give an exploded diagram.

Don't try to take the zoom eyepiece apart as this is more complicated.

I'll see if I have a 40931 HR2. Probably not.
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Old Thursday 27th December 2018, 20:08   #3
Binastro
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A quick look only turned up the 40933 HR2 zoom.

The Opticron website has details of historic and modern eyepieces.
If nothing there, ask Opticron if they can help.
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Old Thursday 27th December 2018, 20:13   #4
Binastro
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If the eyepiece performs well, don't take it apart again unless with great care, as it may have been correctly disassembled and assembled by you first time round.
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Old Thursday 27th December 2018, 20:51   #5
johnphearson
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Thanks Binastro.
The lens seems to work okay now. I wasn’t sure about the first element, It spun as I disassembled, I presume the flat side is outer facing and convex innermost. The same as the 4th element.
I understand how to disassemble now, Flat down and draw the tube upwards leaving elements and spacers stacked.
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Old Thursday 27th December 2018, 22:00   #6
Binastro
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Hi John,
I got it wrong before, but made some tea, and thought I'll be back later.

The Plossl is 2 doublets.
Erfle 3 groups. 2 doublets and a single.

However, I have a 3/4 inch focal length Barr and Stroud, 75 degree field that was used a lot in 1940s military optics I think.
From memory 4 groups, 6 elements. I use it in 2 inch barrel, a fine eyepiece but uncoated so low transmission.

I am not sure about the hard coated 1940s Kodak 38mm wide angle eyepiece that I have in 3 inch barrel.

So your 4 group? eyepiece is maybe a 5 or 6 element wide angle, about 70 degree field?, with some cemented glass.
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Old Thursday 27th December 2018, 22:04   #7
Binastro
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The eye lens rear surface is often flat, but sometimes concave.

The problem with having a stack is it can fall over.
Maybe take a photo when first disassembled in case it topples over.

Last edited by Binastro : Thursday 27th December 2018 at 22:08.
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