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How to replace Eyepieces in Binocular

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#1 big al

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Posted 16 April 2018 - 01:13 PM

now I have a pair of big & bulky Swallow 25-125-80 Zoom Binoculars which are of no use to me ,advertised in classified adds, I don't like zoom binoculars one bit ,and these well are way to strong (zoom wise) that's why I want to sell them, then I had a thought ,would it be possible to take the zoom optics any eye pieces of them, and replace with some x7 0r x6 eyepieces , at 6x80 or 7x80 they would be very useable as astro bins , but ok I am able (I think) to remove the zoom eye pieces and covers ,but how would I go about getting x7 eye pieces to work with them, is I just a case of getting the correct fit? or does everything else ,prism's objective lens etc. all have to be sorted ,

hope there is somebody on here with the expertise to answer the question (please no guessing) if you don't know leave the reply blank until somebody who does know (how too) reply's, then we all get to share there knowledge?

ps have done an internet search but cannot find any answers' concerning the question I asked ,even YouTube drew a blank .

thanks

Al


Edited by big al, 16 April 2018 - 02:38 PM.


#2 Mark9473

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Posted 16 April 2018 - 02:23 PM

Consider changing your thread title to something about exchanging eyepieces on binoculars, otherwise the right people may never get to see your question. Otherwise search for similar threads and PM the people involved such as MartinPond and others.



#3 big al

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Posted 16 April 2018 - 02:33 PM

good point will try to do ,but don't think I can edit thread title

maybe if a mod sees this thread they might be able to add "exchanging eyepieces" to the title thread?

fingers crossed 

Al


Edited by big al, 16 April 2018 - 02:41 PM.


#4 brentwood

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Posted 16 April 2018 - 05:53 PM

 A couple of points here, firstly, a 6x80 or 7x80 binocular would be ineffective as the  exit pupil would be larger than your own eye pupils. As a result, these binoculars would perform as 6x42 or 7x49, assuming your own pupils are 7mm.

Secondly, using eyepieces from 6x or 7x binoculars would NOT result in the same magnification with the 80mm objectives.


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#5 Jawaid I. Abbasi

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Posted 16 April 2018 - 08:15 PM

Title Changed

Well, you can asked Siebert Optics or Denis to do the service for you. Nothing hurt to email or call them for a quote.


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#6 big al

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Posted 17 April 2018 - 10:40 AM

thanks but would the light gathering be really good with a 80mm objective and large exit pupil ? making them ideal night binoculars for star gazing?



#7 Rich V.

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Posted 17 April 2018 - 11:57 AM

The 80mm objective lens' light gathering is limited by your own eye's pupil size as Brentwood pointed out above.  At 7x, an 80mm instrument will provide a ~11.5mm exit pupil.  Even if your eyes still have a large 7mm dilated pupil, you're only going to see the central 49mms of your 80mm objective.  The rest of the light is wasted on your iris and won't reach your retina anyhow.

 

Also, to reach 7x, it would take very long focal length eyepieces to reach such a low power.  It's not a matter of substituting existing binocular eyepieces to fit your binos; bino eyepieces like that were never made.   IIRC, an 11x80 is the lowest mag 80mm bino I've ever heard of for good reason.

 

Rich


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#8 KennyJ

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Posted 17 April 2018 - 12:06 PM

10x80 was a configuration used by German manufacturer Busch in the famous FLAK 45 degree model.

 

However, although I'm far from an expert on the matter, from what I've read, I suspect this venture is doomed from the outset due to the unorthodox and generally very poor quality construction of these type of zoom binoculars.

 

Kenny


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#9 Foss

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Posted 18 April 2018 - 10:35 AM

^^^ and Zeiss's 80° 10 x 80 Kriegsmarine.

 

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#10 Jon Isaacs

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Posted 18 April 2018 - 05:57 PM

^^^ and Zeiss's 80° 10 x 80 Kriegsmarine.

 

A nice shot of Jack's 10x80. At 10x, they're ideal for large aperture hand held use. :)

 

jon


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#11 MartinPond

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Posted 19 April 2018 - 07:17 AM

Any zooms I have scavenged had an

elaborate mechanical construct as well as 

many restrictions in the path width....

 

Seems dicey that you could ever match the phase length through the thing

and come up with a decent focal range at single power.

 

I suppose, if enough if the post-prism mechanics were replaced,

you could make something work.  Not an easy task though,

due to effective length and field restriction..


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