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lens2scope alternative? (mount diagonal/EP on a telephoto lens)

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#1 nicolachel

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Posted 25 April 2018 - 04:14 AM

Just wondering is there an alternative to the lens2scope thing that would allow one to mount a standard 1.25 " or 2" diagonal/EP to a telephoto lens (Like F mount) to turn it into a refractor?

 

As I understand lens2scope has a built in 10mm EP and thus doesn't allow the use of others.


Edited by nicolachel, 25 April 2018 - 04:15 AM.


#2 Mark9473

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Posted 25 April 2018 - 06:41 AM

I like this approach: a diagonal body (nosepiece removed) glued to a rear lens cap with a opening cut into it.

http://www.bobatkins...pe-adapter.html

 

Forget about the 2" option; the lens won't have enough back focus. Nikon F mount has only something like 46 mm to work with.



#3 Mark9473

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Posted 25 April 2018 - 06:46 AM

Here's one with a parts list: http://www.nobell.or...fspottingscope/



#4 nicolachel

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Posted 25 April 2018 - 10:10 PM

Thanks Mark! Thanks like an interesting DIY projectlol.gif



#5 luxo II

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Posted 26 April 2018 - 05:27 AM

Made one once for PK telephoto lenses by cannibalising a slim 5mm metal extension ring to use for the bayonet mount - far stronger than a lens cap and also locks in place so no risk of it falling off in the dark.

Using a jewellers screwdriver, removed the bayonet on the rear of the extension ring and the aperture mechanism then glued a 1.25” eyepiece adapter on the back using araldite - this lasted perfectly for many years.

There’s really no room for star diagonals of any sort - though I did try 1.25” a prism diagonal.

Lenses used were a 135mm f/2.8 - that really had to be stopped down to f/4, so it was really only about 30mm real aperture - and a 500mm f/8 mirror lens which made quite a nice super finder.

Eyepieces that worked well included an old Meade 20mm Erfle and LV 25mm. From memory the RKE 28 and 21 were not able to achieve sharp focus over the full field of view.

Edited by luxo II, 26 April 2018 - 05:35 AM.


#6 TONGKW

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Posted 26 April 2018 - 07:47 AM

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I have built a spotting scope with a old 400 mm f/5.6 telephoto lens, using a Nikon to 1.25” adapter, the front lens from a Celestron 2x Barlow and a 1.25” correct image diagonal.
All my 1.25” eyepiece will come to infinity focus and the image is sharp up to 80x which is good enough for birdwatching.

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Spotting Sun-001.jpg

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#7 TONGKW

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Posted 26 April 2018 - 07:55 AM

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The adapter has fittings for Nikon, Canon and Sony lens and was obtained from this website:-

https://item.taobao....&id=14902366113

I don’t know whether this adapter is obtainable in the US.
The cost of the adapter is RMB166= US$30 approximately plus postage.

﹣﹣﹣﹣

 

 

Attached Thumbnails

  • GRUS 相機鏡  1.25吋接口.jpg
  • GRUS 1.25-inch adapter.jpg
  • GRUS 1.25-inch adapter.jpg
  • GRUS 1.25-inch adapter.jpg
  • GRUS 1.25-inch adapter.jpg
  • GRUS 1.25-inch adapter.jpg

Edited by TONGKW, 26 April 2018 - 07:57 AM.


#8 TONGKW

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Posted 26 April 2018 - 08:02 AM

﹣﹣﹣﹣

I am sorry that the image of the adapter has been posted too many times. 

But it appears that I am not able to  delete the surplus images.

﹣﹣﹣﹣



#9 patta

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Posted 16 September 2018 - 09:56 AM

Very very interesting! Thanks all for posting

 

Last year I couldn't find the Taobao adapter and I had to make it myself.

 

Takes the Adaptall conic lens mount; I used it with M42 lenses; on the other side 1,25 eyepiece. Tapped an hole for tripod screw.

No Barlow, the image gets inverted; nobody liked except me!

I did it for afocal photography with the mobile phone, since I couldn't find monoculars with really wide field.

When I have time I'll try to put an erecting prism - without Barlow if I manage.

 

Here it the photo, hope it is visible

 

20180916 164244
Album: Afocal experiments 2017
2 images
0 comments



#10 patta

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Posted 20 September 2018 - 04:19 AM

By the way, one of the best Lens - as  - scope that I can imagine is:

 

   A reflex camera itself!

 

After all, it has the pentaprism and (in some models) also a fairly good eyepiece.

It can also take photos if needed!!  You can control aperture an focus in automatic lenses! Can have autofocus!!

 

Well yes it's heavy and the finder is a bit unconfortable, a 45 deg is better for use as terrestrial scope. Solution: see the image in live-view on the screen.

Am I missing the purpose of lens2scope?



#11 Snath

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Posted 20 September 2018 - 05:42 AM

Looking through the viewfinder cedes some light in the only‐partially‐silvered mirror (has to pass some light for the autofocus sensors behind it) and in the focusing screen.

 

Field of view is also lost—more than forty percent on a 35 mm camera, in cropping the image circle to a 3:2 rectangle.



#12 patta

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Posted 21 September 2018 - 09:18 AM

Agree! But look how small is the entrance of the lens2scope; its a 10mm eyepiece!  Much more cropping than a camera viewfinder.

 

To have (almost) the full field with no light loss, the only way is to have the eyepiece directly on the image plane: no prism, inverted image.

To match the 35mm (virtual) image needs a 2" eyepiece & large field lens (thus long FL, 30+ mm) to have the full field & light, but I didn't try; Just 1.25" eyepiece, max 20mm.




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