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Short FL objective lens use

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14 replies to this topic

#1 nimitz69

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Posted 20 July 2020 - 05:38 PM

So has anyone ever tried an objective for their NVD shorter than 25mm? If so, how did it turn out? I have an opportunity to get my hands on a 12mm f/1.2 c-mount lens but don’t know if its worth it ...

#2 a__l

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Posted 20 July 2020 - 06:35 PM

I am also curious about this question. Most likely depends on the quality of the lens. Perhaps I will move slowly towards this.
I am currently looking for the best 25mm lens for afocal.



#3 nimitz69

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Posted 20 July 2020 - 07:37 PM

I think its hard to beat an ENVIS f/1.2 lens as it was designed for use with NVDs and the fact that the TVNC afocal adapter for TV EPS was designed to be used with it is a nice bonus. It really makes afocal easy - assuming you have TV EPS of course.

#4 a__l

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Posted 20 July 2020 - 07:45 PM

I'm not worried about the adapter problem. I can make anyone. In my opinion the use of Envis in observational astronomy is based on the PSV-14, which is difficult to use without a lens. But there is a caveat, Envis was developed for specific purposes, one of which is light weight. This does not always contribute to the best optical performance. Perhaps there are better quality lenses (?) I don't know yet.

 

Ps. It would be nice if mr. Nagler thought in this direction :)


Edited by a__l, 20 July 2020 - 07:59 PM.


#5 Eddgie

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Posted 20 July 2020 - 07:57 PM

I'm not worried about the adapter problem. I can make anyone. In my opinion the use of Envis in observational astronomy is based on the PSV-14, which is difficult to use without a lens. But there is a caveat, Envis was developed for specific purposes, one of which is light weight. This does not always contribute to the best optical performance. Perhaps there are better quality lenses (?) I don't know yet.

The ENVIS optical elements are the same as those used in the PVS-14 and PVS-7. Even part of the housing is the same.


Edited by Eddgie, 20 July 2020 - 07:58 PM.


#6 a__l

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Posted 20 July 2020 - 08:08 PM

Actually, I am writing about this.



#7 Mike Lockwood

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Posted 20 July 2020 - 08:12 PM

I think its hard to beat an ENVIS f/1.2 lens as it was designed for use with NVDs and the fact that the TVNC afocal adapter for TV EPS was designed to be used with it is a nice bonus. It really makes afocal easy - assuming you have TV EPS of course.

+1

 

The objective lens was developed to win government contracts, and provides a good image across the field at a very low f/# across a good part of the visible spectrum.  That is not easy.  I know of no better lens for this application.  If there were one, I suspect one would be paying $1k-$2k for it if it were even available for purchase.



#8 cnoct

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Posted 20 July 2020 - 09:42 PM

I do believe quite a few have and with good results, myself included. 

 

For me personally, in pursuits such as meteor watching and aiding TLE spotting, dropping down to 16mm has been enormously beneficial. Those few extra degree of FOV make for a significant difference, sure the magnification reduces  image scale but it's so much easier to quickly locate the altitude of TLE activity. As for meteor showers, well image scale is less important than FOV, at least for the way I find most pleasing. So for specific use cases, short FL lenses are extremely useful. 

 

Shorter FL objectives also have benefits for afocal so long as one maintains an ideal the exit pupil to entrance pupil ratio. There will be a loss in AFOV but if one wants to relay the exit pupil as close to one to one, then higher resolution and system efficiency can be achieved. Say I have a system that results in the formation of a 7mm exit pupil, well if I pair that with a 27mm FL objective with an entrance pupil of ~22mm, then that objective expands that 7mm exit pupil to ~19mm resulting in a lower the photon density over any given area of the photocathode. However, if I were to use a 16mm FL objective with a ~ 9mm entrance pupil, well now that 7mm exit pupil, from the exit pupil forming system, is expanded to ~10mm where photon density is relatively preserved.

 

 

So has anyone ever tried an objective for their NVD shorter than 25mm? If so, how did it turn out? I have an opportunity to get my hands on a 12mm f/1.2 c-mount lens but don’t know if its worth it ...

 

IDK but for me personally 12mm is pushing it, I'm good at 16mm but shorter than that becomes less tolerable and the gains to me are not as great, at least for hand to eye visual use. Will definitely get you a very wide FOV but might want that to be a static configuration or remote viewing/capture system.

 

Not often one comes across a good 12mm f/1.2 with a sensor format greater than 2/3" so might as well try it. 

 

NVD Micro with 16mm Objective.jpg



#9 a__l

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Posted 20 July 2020 - 11:16 PM

+1

 

The objective lens was developed to win government contracts, and provides a good image across the field at a very low f/# across a good part of the visible spectrum.  That is not easy.  I know of no better lens for this application.  If there were one, I suspect one would be paying $1k-$2k for it if it were even available for purchase.

This is not relevant to me. I cannot buy Envis for known reasons.
From user testing on the internet (hunters), I can see that the COT NVM-14 lens is better at the edge than the PSV-14. This of course still depends on the honesty of the testers. I couldn’t find this lens on the market. Lens of mine has problems at the edge I don't like.

Probably users who can spend 10K for NV can add 1-2K more if that makes sense.


Edited by a__l, 20 July 2020 - 11:21 PM.


#10 AllStarez

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Posted 21 July 2020 - 10:16 AM

I do believe quite a few have and with good results, myself included. 

 

For me personally, in pursuits such as meteor watching and aiding TLE spotting, dropping down to 16mm has been enormously beneficial. Those few extra degree of FOV make for a significant difference, sure the magnification reduces  image scale but it's so much easier to quickly locate the altitude of TLE activity. As for meteor showers, well image scale is less important than FOV, at least for the way I find most pleasing. So for specific use cases, short FL lenses are extremely useful. 

 

Shorter FL objectives also have benefits for afocal so long as one maintains an ideal the exit pupil to entrance pupil ratio. There will be a loss in AFOV but if one wants to relay the exit pupil as close to one to one, then higher resolution and system efficiency can be achieved. Say I have a system that results in the formation of a 7mm exit pupil, well if I pair that with a 27mm FL objective with an entrance pupil of ~22mm, then that objective expands that 7mm exit pupil to ~19mm resulting in a lower the photon density over any given area of the photocathode. However, if I were to use a 16mm FL objective with a ~ 9mm entrance pupil, well now that 7mm exit pupil, from the exit pupil forming system, is expanded to ~10mm where photon density is relatively preserved.

 

 

 

IDK but for me personally 12mm is pushing it, I'm good at 16mm but shorter than that becomes less tolerable and the gains to me are not as great, at least for hand to eye visual use. Will definitely get you a very wide FOV but might want that to be a static configuration or remote viewing/capture system.

 

Not often one comes across a good 12mm f/1.2 with a sensor format greater than 2/3" so might as well try it. 

 

attachicon.gifNVD Micro with 16mm Objective.jpg

 

Really interesting for meteor watching. What particular lens do you actually use with success ?



#11 cnoct

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Posted 21 July 2020 - 09:39 PM

My favorite, as of today, is a Schneider-Kreuznach Cinegon 16mm f/1.8.

 

I'm on Schneider kick right now so that's not to say others haven't been favorites of a time. At a maximum of f/1.8 is pushing edging on the slow side though I also use a f/2.0 fixed aperture version and would say that's about my limit for intended use of this focal length. The vast majority of machine vision 16mm I've gone through worked just as well. What I never had work well for me was the wide angle converter, though didn't try many so might be a viable option for some.

 

Better image of the lens than in the hand held configuration posted earlier. 

 

Wide Ange NV Capture System.jpg

 



#12 AllStarez

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Posted 22 July 2020 - 07:17 AM

Nice pics, and thanks for the references. It sounds hard to find out there, and rather expansive. I have found these ones in the second-hand market, have you experienced any by chance ?

 

Computar TV Lens 16 mm f1 .4

Cosmicar Mini TV 16 mm f/1.6

rioma TV Metal 16 mm F1.4 Made in Japan

Taylor Hobson Serital 1,  f1.9 C-Mount 16 mm



#13 PEterW

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Posted 22 July 2020 - 02:26 PM

Cnoct, what’s the cost for these sort of lenses as for
Meteor shower watching you want as much field of view that you can get.

Peter

#14 nimitz69

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Posted 22 July 2020 - 04:49 PM

Well I have a Fujinon 12mm F/1.2 lens inbound so it will be interesting to see how it performs. All I’ll need now is some meteors ...

#15 cnoct

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Posted 23 July 2020 - 08:09 AM

Here's to hoping the sensor format on that inbound Fujinon is =/> 1" sensor format (16mm diagonal), being both 12mm and f/1.2 makes that unlikely but hey fingerscrossed.gif.




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