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Can a PVS-14 objective be converted to an "Envis lens" ?

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#1 ArsMachina

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Posted 24 May 2021 - 03:50 PM

I am actually at the fence about buying two monocular NV devices to be used mainly with my APM 150 SD binoculars.

 

I want to have the option of prime usage as well as afocal usage (beside using 1x,  C-Mount and SLR lenses) so I need a device with a detachable C-Mount objective.

 

As I am living in Germany the Mod.3 is not available for me.

The Mini 14 has no manual gain what I believe to be necessary for astro use.

So I will go with the OVNI-M device

 

From all what I have read so long the PVS-14 Objective and the Envis lens are considered to be very good regarding their threaded front which can be attached to the Televue adapter for afocal use.

 

Unfortunatey the Envis lens is out of production and very hard to find, especially in Europe :-(

 

When I am comparing pictures of the Envis lens and the PVS-14 objective I see the design is quite similar, except of the mounting threads:

 

gallery 139776 8407 45080
 
K1600 DSC00982 1
 
As I have good skills and a lathe which can cut threads I am asking myself if it would be possible to convert an original PVS-14 objective, which is easily available, with a C-Mount thread to work with a Mod.3 or in my case an OVNI-M
 
Mechanically I do not see a problem to cut away the red marked part of the PVS-14 objective and add an adapter with C-Mount thread here.
 
But the big question is, will it come to focus with a Mod.3 and OVNI-B ???
 
Hopefully someone knows more about these two lenses and especially about their focus points.
 
Jochen

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#2 maxmir

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Posted 24 May 2021 - 09:41 PM

I am planning to test using PVS 14 lens with C mount adapter that I will make soon
I think that It should work fine
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#3 ArsMachina

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Posted 25 May 2021 - 01:29 AM

That sounds interesting, Maxmir.

 

Please keep me informed about your results, so I can go the same way.

 

Thank you Jochen



#4 Gavster

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Posted 25 May 2021 - 02:45 AM

See post 25 of the attached thread for a bit of information about what’s required to convert a pvs-14 to envis type lens

https://www.cloudyni...eedback-please/



#5 PEterW

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Posted 25 May 2021 - 03:22 AM

I’d stick to afocal, it’ll turn the f5.5 into F2.2 and make the nebulae shine. Try to get (roughly) matched tubes… don’t need exact specs. Two eyes really pull out the faint wispy stuff better than one! Prime is nice for avoiding fling stacks in the scope and for using camera lenses, but it can’t match the speed.
Wonder if the limited APM helical focus could prove an issue?

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#6 maxmir

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Posted 25 May 2021 - 03:32 AM

Looking at the old thread, it said the C mount adapter would require turn down the diameter PVS-14 lens. Did anyone do this yet?

#7 cnoct

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Posted 25 May 2021 - 04:24 AM

Yes, NVEC had this done when they had the objective assembly manufactured for the ENVIS (M-703E) program.

 

Aside from the fine focus threads and adapter, the lens is the same as the original AVIMO and Thales PVS-14 objective. 

 

Looking at the old thread, it said the C mount adapter would require turn down the diameter PVS-14 lens. Did anyone do this yet?

 

There's enough in the wall to safely do this, I've had ANVIS lenses turned down a tad bit more that this requires. 

 

It's a worthy project.



#8 ArsMachina

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Posted 25 May 2021 - 04:42 AM

I’d stick to afocal, it’ll turn the f5.5 into F2.2 and make the nebulae shine.

Peter, I am talking about afocal here, but for afocal a lens in the NV device is needed.

 

If the issue to convert a PVS-14 objective into an "Envis" is just about the diameter I am save.

The OVNI-M has a thread diameter of 31mm what is way bigger than C-Mount (around 25mm)

 

My concern was the focus position but now I am quite sure that I will be able to use PVS-14 objectives with the OVNI-M

 

Thanks for all your help!

 

Jochen



#9 ArsMachina

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Posted 25 May 2021 - 07:02 AM

Here are two pictures Jonathan did send me, I believe they make it clear.

Here is the front part of the OVNI-M with the 31mm diameter thread:

 

189337296 843871859811256 5835933535888986154 N
 
And here it is with the 31mm to C-Mount adapter screwed in, you see C-Mount has a way smaller diameter:
 
189567114 1696097180582254 6381079504436244611 N
 
This means the PVS-14 Objectives can be adapted to the OVNI-M without problems of the lens diameter what seems not to be the case if one wants to adapt the PVS-14 objective to the smaller C-Mount threads.
 
I hope this helps to understand what I am planning to do :-)
 
Jochen

Edited by ArsMachina, 25 May 2021 - 07:03 AM.

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#10 a__l

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Posted 25 May 2021 - 07:24 AM

My M31 adapters I made myself
Zeiss-Tevidon lens, M42 (prime focus), two different c-mounts (for Fujinon and Nikkor).

Attached Thumbnails

  • Adapter_M31.jpg

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#11 MJB87

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Posted 25 May 2021 - 08:09 AM

Let's please stay on topic. This is a topic specifically to the modification of a PVS-14 objective to fit a Mod3.C or OVNI-M device. Posts dealing with other issues will be removed. Users are always welcome to start a new topic in this or another appropriate forum.



#12 a__l

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Posted 25 May 2021 - 08:10 AM

I hope this helps to understand what I am planning to do :-)

 
 

 

Really curious. There is a nuance. Clamp the lens in a lathe. I hope you write in detail.



#13 maxmir

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Posted 25 May 2021 - 08:41 AM

Clamping it in the lathe is tricky.  I have done this with a small lens in an aluminum cell without damage. This is plastic. I might have to disassemble it



#14 a__l

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Posted 25 May 2021 - 09:32 AM

There are other problems here. You need a clean room. There is a lot of dust in a normal room. In addition, it is necessary to correctly maintain all distances between the 8 elements of the lens. This may result in the inability to use the lens in the future.



#15 maxmir

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Posted 25 May 2021 - 10:10 AM

It would be easiest if you can chuck up the lens cell without taking it apart. The grip on the lathe without cracking the lens is the key.

A six jaw chuck would be nice if you have one.

I suspect the outer cell will cut and thread with very light pressure at minimum speed.

 

I see disassembly biggest problem for most people. The o rings often need special tools.

Most lens have spacers for distance. Dust can be keep under control with great care. Clean room is nice but not required.

Recording the position and orientation of each lens element is required. It can be done. But your right; it might not come back together perfectly.

 

Perhaps explains why we don't see this solution for the mod3c.


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#16 ArsMachina

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Posted 25 May 2021 - 10:20 AM

I am very experienced in clamping plastic.

I do have a 6x chuck for safe clamping with low pressure for such jobs:

 

13355 0

 

Taking apart the objective would be an option, I did this for other jobs in the past, but here I believe it is not necessary.

 

Jochen


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#17 maxmir

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Posted 25 May 2021 - 10:24 AM

I think figured out how to do this on the lathe! 

 

Make a part the fits into front of lens using the filter thread as the holder / grip piece.

You have to turn and thread in a direction so it won't unscrew. I made this already for an afocal adapter.

Just cover the lens to protect it against chips


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#18 a__l

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Posted 25 May 2021 - 10:32 AM

ArsMachina, Yes!

I thought about it, but you got ahead of me :)
I only have a standard, 3 pcs cam.



#19 ArsMachina

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Posted 25 May 2021 - 11:05 AM

Fortunately my workshop is very well equipped :-)

 

I bough this 6 piece chuck not long ago at Ebay.

They are chinese produced and quite cheap.

Not the very best quality but for sensitive parts from time to time they are good enough and very helpful

 

Jochen



#20 GeezerGazer

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Posted 25 May 2021 - 11:18 PM

Jochen,

The Envis lens appears to be glass-reinforced resin, which is among the most tricky of plastics to machine.  The best cutters for glass-fiber-filled plastic materials have positive rake angles and very sharp cutting edges.  As with all plastics, avoid heat buildup with lower speeds.  Glass-reinforced resin also causes dust when machined, so if you do not have a dust evacuation system, you might consider wearing a respirator. 

 

I'd like to read about your success and any issues you encounter... I hope you will post here after you have made the adapter.  

Ray


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#21 ArsMachina

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Posted 26 May 2021 - 02:17 AM

I will use a mask while machining plastic.

 

Do you know if the original PVS-14 objective is made out of the same material?

 

Jochen



#22 cnoct

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Posted 26 May 2021 - 02:34 AM

Aluminum same as the ENVIS

.

On the ENVIS, except for the Ultem of the focus sleeve and infinity stop ring, the entire assembly, lens tube/body is all aluminum.

 

The part and material being machined is aluminum.


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#23 ArsMachina

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Posted 26 May 2021 - 03:06 AM

That is interesting, cnoct, I did not expect any aluminium there but only plastic.

But Aluminium is way batter to machine and cutting threads.

 

Jochen



#24 maxmir

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Posted 26 May 2021 - 07:40 AM

That make things easier.

Thanks Cnoct



#25 a__l

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Posted 13 July 2021 - 06:43 PM

 

I am actually at the fence about buying two monocular NV devices to be used mainly with my APM 150 SD binoculars.

 

I want to have the option of prime usage as well as afocal usage (beside using 1x,  C-Mount and SLR lenses) so I need a device with a detachable C-Mount objective.

 

As I am living in Germany the Mod.3 is not available for me.

The Mini 14 has no manual gain what I believe to be necessary for astro use.

So I will go with the OVNI-M device

 

From all what I have read so long the PVS-14 Objective and the Envis lens are considered to be very good regarding their threaded front which can be attached to the Televue adapter for afocal use.

 

Unfortunatey the Envis lens is out of production and very hard to find, especially in Europe :-(

 

When I am comparing pictures of the Envis lens and the PVS-14 objective I see the design is quite similar, except of the mounting threads:

 

 
 
 
 
As I have good skills and a lathe which can cut threads I am asking myself if it would be possible to convert an original PVS-14 objective, which is easily available, with a C-Mount thread to work with a Mod.3 or in my case an OVNI-M
 
Mechanically I do not see a problem to cut away the red marked part of the PVS-14 objective and add an adapter with C-Mount thread here.
 
But the big question is, will it come to focus with a Mod.3 and OVNI-B ???
 
Hopefully someone knows more about these two lenses and especially about their focus points.
 
Jochen
 

I am very experienced in clamping plastic.

I do have a 6x chuck for safe clamping with low pressure for such jobs:

 


Taking apart the objective would be an option, I did this for other jobs in the past, but here I believe it is not necessary.

Jochen

 

ArsMachina,

From a mechanical point of view, there are several options for the original PVS-14 objective.
You will not be able to thread M31x0.75 on any of them.
In your picture, the objective is presumably ITT. You run the risk of trying to thread a c-mount on it. Most likely it will fall apart. Also, you need a stop plane when focusing at infinity. My first attempt ended in disaster. I will be thinking about a objective from another manufacturer. Need to think about an intermediate adapter (I). To connect with the body of NV.

 

Better to make an adapter (II) for the front of the PVS-14 lens and attach the chuck to it. This will provide a reliable fit for cutting with any chuck. In the future, use this adapter (II) for attaching to TV 55 for afocal (for example). Remove the cone from this eyepiece, there is a metric thread. Make a mating thread on this adapter(II) to attach to this eyepiece.


Edited by a__l, 13 July 2021 - 07:10 PM.

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