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New NV optical accessory from Televue

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#1 phonehome

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Posted 27 February 2020 - 10:05 PM

In case anyone missed it, there is a new NV optical accessory on the horizon from Televue.  It easily modifies a 55mm TV plossl into a 67mm exclusively for NV use.  This both increases the field of view and reduces the image size projected on a NV objective.  If my calcs are correct it is optimal for something around f/3.3 which results in about a 20mm exit pupil for the NV objective.  Of course it'll work for other f/ratios too.

 

Mike Lockwood has the info from Televue released to date.  Go to the very end of his article (However if your into NV I recommend reading the whole article):

 

http://www.loptics.c...on.html#Feb2020

 

I understand a prototype was tested at WSP.  Maybe we'll get some feedback.

 

Thank you uncle Al (and Mike)!

 

Ed


Edited by phonehome, 27 February 2020 - 10:20 PM.

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#2 Jeff Morgan

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Posted 28 February 2020 - 02:12 AM

A very long Plossl is not exactly a new invention. Russell Optics already makes 65, 72, and 85mm Plossls that can provide very large exit pupils for a NVD.

 

I am not getting what the selling point is on this?

 

Is there any improvement in edge-of-field performance? That would make it highly desirable.


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#3 PEterW

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Posted 28 February 2020 - 08:39 AM

It scrapes the light from the plossl that would miss the 40degree field of view of the NV objective and pokes it into the NV system, effectively lengthening the plossl and enabling greater focal reduction for brighter image. NV is still a niche and so we can’t expect things like custom eyepieces specifically for us, but we can get small tools that help us.. witness the “TV-TNVC adapter” and now this novel optic. There are other long focal length EP out there and probably other approaches to NV we’ve not tried, let’s keep experimenting!

I understand we’ll get a WSP experiences report soon and then we can start saving for product release.

Peter
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#4 The Ardent

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Posted 28 February 2020 - 11:11 AM

Maybe they will have it at NEAF. 



#5 PEterW

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Posted 28 February 2020 - 12:37 PM

Ask David!

Peter

#6 hoof

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Posted 28 February 2020 - 11:57 PM

Interesting.  

 

One day I hope they release an updated TNVC adapter that has a bigger opening.  The current one has about a 15mm opening, meaning that the biggest exit pupil that a NV device with an ENVIS lens can take is 15mm, well short of the 18-20mm theoretical maximum.  Not sure why they did this, could be light baffling or something, as the opening looks like a light baffle.

 

A 67mm effective TV Plossl on a F/4 light cone would yield an effective F ratio of 1.6, with an exit pupil of 17mm (assuming 27mm focal length for the ENVIS), so too big for the TNVC adapter, by about 1-2mm.  At 67mm, you'd need F/4.5 or smaller to fit into the TNVC adapter opening.  Basically, unless you have F/4.5 or higher focal ratio for your telescope, I would stick with the naked 55m configuration.



#7 PEterW

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Posted 29 February 2020 - 03:34 AM

Interesting... have to see how they get round this and what the new unit looks like. I am sure there are many of us with <f4.5 scopes hoping to go <f2.

Peter

#8 Mike Lockwood

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Posted 29 February 2020 - 08:02 PM

Al reported that it does improve the quality at the edge of the field of view.  So consider it a sort of corrected long plossl.

 

I will post images if I can get a sample to test.  As I understand it, they are working to make sure that it will fit 55mm Plossls from long ago up until present, machined by different suppliers, probably.

 

Stay tuned.


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