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turning camera lenses into visual refractors

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#1 joelin

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Posted 29 November 2019 - 03:26 AM

has anyone ever tried to turn a camera lens such as a Nikon into a refractor with visual capability using eyepieces?

 

I feel like I am close, see: https://photos.app.g...8oQmVsbFuEAQQB9

 

Its basically: Nikon lens -> ZWO Nikon adapter -> top of coma corrector (theres no glass here, just a holder) -> eyepiece

 

between the Nikon adapter and the top of the coma corrector I'll need an M42 female to M48 male adapter which I can get from scopestuff here: http://www.scopestuff.com/ss_4248.htm

 

The question is: will all of this come to focus?

 

how about If I use it with a daystar quark? will it come to focus? i wonder because with the daystar quark, I always add in some extension tubes at the focuser...and I'm thinking this extra length (via coma corrector holder) is also the same as that extra length?


Edited by joelin, 29 November 2019 - 03:45 AM.


#2 havasman

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Posted 29 November 2019 - 03:51 AM

I took a Zeiss Tele-Tessar f3.5 200mm, a C/Y extension tube and an ES82 18mm and made an interesting tool of them. I don't remember which length extension worked. The whole thing was a bit clunky but it was fun to try. It worked too. I remember NGC869/884 being very finely rendered.



#3 Jarno

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Posted 29 November 2019 - 05:57 AM

It's possible but challenging since you only have 46.5mm of backfocus to work with. Bynolyt offers an adapter called lens2scope which does an OK job but introduces some chromatic abberration. You also can't exchange the eyepiece so you have a fixed magnification of focal length / 7. 

 

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#4 Uwe Pilz

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Posted 29 November 2019 - 02:50 PM

The most important problem are the different design aims: A refractor is diffraction limited at the axis. A telephoto lens tries to receive a decent mapping in the field. Telephoto lenses are not diffraction limited, until stopped down remarkably.

 

So you may build a wide filed scope form such a lens. But every cheap FH refractor will give you better results.


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#5 joelin

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Posted 29 November 2019 - 03:55 PM

Yes but can't find a refractor under 300mm focal length while.camera lenses can

#6 Uwe Pilz

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Posted 29 November 2019 - 04:45 PM

> but can't find a refractor under 300mm focal length

 

May be a a finder or a a binocular lens are choices.


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#7 BillP

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Posted 29 November 2019 - 05:09 PM

I have a bunch of the old manual and AIS and E Nikon SLR lenses.  To have fun with them as spotters or astronomy I just got the two items linked to be able to put an eyepiece on the end of them.

 

https://www.ebay.com...CCABEgJBmfD_BwE

 

https://www.ebay.com...BCABEgKvRvD_BwE



#8 joelin

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Posted 29 November 2019 - 05:40 PM

Oh neat.
We're you able to reach focus at infinity with those adapters?

#9 Jarno

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Posted 29 November 2019 - 07:17 PM



Yes but can't find a refractor under 300mm focal length while.camera lenses can

How about this one or this one? So, they do exist.

 

Jarno 


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#10 james7ca

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Posted 01 December 2019 - 01:20 AM

Kenko sells a 200mm f/4 lens that they outfit for use as a telescope. I purchased the t-mount version of that lens a few years ago for just over $100 direct from Japan. Unfortunately:

 

1.) It has a lot of chromatic aberration and I don't think it would make a good telescope (it's a four-element design, but as Uwe Pilz said camera lenses aren't really designed to operate as telescopes).

2.) I can't find any reasonable pricing on this lens anymore, seems like the retailers now want something like $300 for it which is kind of ridiculous.

 

That said, it was a pretty good value at the price I payed and it's actually a decent scope for wide-field, narrow-band astrophotography.

 

Here is a listing on eBay for the telescope version of the lens (at $363):

 

  https://www.ebay.com...id=223121964318



#11 joelin

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Posted 01 December 2019 - 03:40 AM

How about this one or this one? So, they do exist.

 

Jarno 

I've thought about going even much lower...like sub 100mm... mostly because I might want to try putting a night vision device into a relatively wider lens....50mm would be nice for viewing the core of the milky way



#12 Jon Isaacs

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Posted 01 December 2019 - 05:17 AM

I've thought about going even much lower...like sub 100mm... mostly because I might want to try putting a night vision device into a relatively wider lens....50mm would be nice for viewing the core of the milky way

 

In general, one difficulty with using a camera lens as a telescope is that there is not enough backfocus to use a diagonal, you're stuck viewing straight through.  

 

But it seems you're not really looking to use this as a telescope, rather you are going to use it as a camera lens...  Camera lenses work quite well as camera lenses.. :)  

 

Jon


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#13 joelin

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Posted 01 December 2019 - 09:42 AM

I’d prefer having a diagonal a when it comes to night vision actually....maybe I can use a Barlow to push the light out? 



#14 noisejammer

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Posted 01 December 2019 - 10:04 AM

I’d prefer having a diagonal a when it comes to night vision actually....maybe I can use a Barlow to push the light out? 

The problem is that a camera lens extender is designed to keep the lens register at the same place.

 

Some older telephoto lenses have quite a long gap between the lens mount and the furthest back optical element. You can sometimes remove the mount (for example, the old Tamron Adaptall series.) You might me able to get more space that way.

 

Another option might be an obsolete medium format lens - say something like a Contax 645 with 64mm . These have excellent optics and are available from KEH (presumably among others.) Here's a 140mm f/2.8. You could also look at Pentax, Pentacon, Mamiya and even Hasselblad  or Bronica offerings.



#15 daquad

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Posted 04 December 2019 - 12:30 PM

I used a Telesar Extension tube with the eyepiece adapter linked by Billp to use with my ancient Vivitar 200 mm f/3.5 manual telephoto.  Only straight through viewing, though.

 

Dom Q.

 

Viv 200 f3.5.JPG



#16 jgraham

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Posted 04 December 2019 - 01:23 PM

Here's a throwback... it used to be fairly common to use surplus lenses from photocopiers for camera lenses and small refractors, so-called CopyScopes. This is one that I used as a satellite tracking scope for many years before I replaced it with an Orion StarBlast...

 

CopyScope-1.jpg

 

Note the scales that I used to set the altitude and azimuth. :)


Edited by jgraham, 04 December 2019 - 01:24 PM.


#17 BillP

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Posted 04 December 2019 - 03:58 PM

Oh neat.
We're you able to reach focus at infinity with those adapters?

 

Depends on the lens, but yes reaches infinity focus.



#18 SonnyE

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Posted 05 December 2019 - 11:02 AM

Thinking about this, I suggest putting the lens on it's appropriate camera and look through that.

I do that with my Tamron 150-600 mm from time to time.

Also, if your eyes are younger than mine (and most are), there is live view on the back of my D3300. wink.gif


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#19 joelin

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Posted 05 December 2019 - 12:12 PM

Yes but it’s usually not as sensitive unless you expose for long time

#20 Jeff Morgan

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Posted 05 December 2019 - 02:24 PM

Very easy to do with a NV eyepiece. And popular since camera lenses have very fast focal ratios. Just need a $20 Canon (or Nikon) to C-mount adapter.

 

If you wanted to use a conventional eyepiece, Precise Parts could make the telephoto adapter. Telephoto on one side, 2" or maybe T2 on the back side. Attach a Baader Click Lock adapter. You'll also need to know the flange to focal plane distance for your lens.

 

https://en.wikipedia..._focal_distance

 

The issues are:

 

1) Camera lens will (usually) require some form of mount due to weight and magnification;

2) You'll need to plan your adapter such that the eyepiece can come to focus within the flange to focal plane distance of your chosen lens; and 

3) The camera lens is essentially a straight-thru refractor, with insufficient room for a star diagonal. You'll need a front-mounted flat to achieve right angle function.

 

But is is doable.

 

IMG_3043.jpg
IMG_1132.jpg
IMG_9245.jpg
IMG_6565.jpg

 


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#21 joelin

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Posted 05 December 2019 - 09:11 PM

nice photos~!

 

do you have to try to worry about getting exactly 55mm backspacing when using canon/nikon lenses with the NVD? or is it fine just to get close to it and then adjust your focus? what spacing do you end up having?



#22 slavicek

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Posted 06 December 2019 - 03:27 PM

Joelin,

as I've posted elsewhere, here is one for you:

 

canon1-8-nv.JPG

 

White phosphorus NV + C-mount to Canon EOS adapter + 200mm F/1.8 Canon

or if you like, you can use it with "regular" eyepiece:

 

canon1-8-11.JPG

 

Nagler 11 mm + C-mount to Canon EOS (holds eyepieces too) + 200mm F/1.8 Canon

 

So, which one are you going to go for? Let me know so I can help you with the filter holder.




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