86 replies to this topic

[cnoct]

Historically, there's been no simple nor widely accessible method of adapting a PVS-14 for use in Prime night vision astronomy. 
 
For the many times I've been asked... "how do I adapt my PVS-14 for Prime focus"... My answer has usually been, you don't, use it as is and enjoy.   
 
That is not to say a PVS-14 couldn't be adapted to Prime, it certainly could, see this thread: https://www.cloudyni...per-14-chassis/ 
 
So why have I shot down such adaptations... Simple, no off-the-shelf parts to turn a custom DIY into an every able and willing persons DIY. 
 
After years of being widely inaccessible, here's an accessible, off-the-shelf DIY, for mechanically mounting a PVS-14 in Prime:
 
 PVS-14 Prime: An EZ DIY

• TRYBE Optics Mounting Latch - https://www.opticspl...ng-latches.html
• Generic 30-to-42mm Step Ring - https://www.amazon.c...r/dp/B009AKU3EE
• T2 to 2" Adapter (preferably zero optical length) - https://agenaastro.c...2-m48-22-5.html

 

• Remove native/oem objective lens 
• Thread all relevant components together
• Tighten set screw on latch 
• Orient TRYBE mounting latch over infinity set ring, affix by closing latch

Just because it's possible doesn't make it practical, this is not for those who don't really, really, really want it!

Edited by cnoct, 02 May 2022 - 10:55 AM.

[cnoct]

 

[cnoct]

 

[Joko]

Hi Cnoct, 

Great mod !

Last year I've been able to modify PVS-14 for prime use too.

 

But there is an issue to focus it in telescopes.

The reason is the distance between the photocathode and the focal point of the telescope is huge. I measured it to 35mm.

So backfocus is a real issue and i don't know if there are a lot of telescopes that can allow this.

 

Also with your method can you rescrew the oem objective lens and switch from prime to afocal easily ?

 

Last but not least it requires additional tools to do the mod and would void the warranty as people will have to remove the intensifier tube to remove the inner ring that holds the lens.

Edited by Joko, 02 May 2022 - 07:43 AM.

[a__l]

But there is an issue to focus it in telescopes.

The reason is the distance between the photocathode and the focal point of the telescope is huge. I measured it to 35mm.

So backfocus is a real issue and i don't know if there are a lot of telescopes that can allow this.

 

Any Newt allows it.

Dist 47 mm https://www.televue....id=61&Tab=_phot

Use this adapter for P2 https://agenaastro.c...-4-trg1072.html You may need an extension ring.

Edited by a__l, 02 May 2022 - 08:09 AM.

[Joko]

Any Newt allows it.

Dist 47 mm https://www.televue....id=61&Tab=_phot

Use this adapter for P2 https://agenaastro.c...-4-trg1072.html You may need an extension ring.

It seems not, it didn't work in all Newtonians I tried.

Unless if i use a barlow but the magnification and FOV are not the same.

Edited by Joko, 02 May 2022 - 08:45 AM.

[a__l]

It seems not, it didn't work in all Newtonians I tried.

Unless if i use a barlow but the magnification and FOV are not the same.

You removed the P2 head, replaced it with the adapter from the link above and it didn't work? Then your 35mm contradicts the 47mm from the Televue website.
The P2 works with any newt and has a 47mm back focus for all.

 

Unless, of course, Newton's design allows the use of P2!

Edited by a__l, 02 May 2022 - 09:04 AM.

[Joko]

You removed the P2 head, replaced it with the adapter from the link above and it didn't work? Then your 35mm contradicts the 47mm from the Televue website.
The P2 works with any newt and has a 47mm back focus for all.

 

Unless, of course, Newton's design allows the use of P2!

In Newtonians there is no need to use a paracorr to reach focus with glass eyepiece. But with PVS-14 in prime i couldn't reach focus in any Newtonians I tried.

So I don't understand why you speak about the P2. I don't have any and never spoke about it in my previous posts.

Edited by Joko, 02 May 2022 - 10:31 AM.

[cnoct]

Thank you, very thoughtful points.

For the most part, yes, I'd say issues you've identified do speak to other reasons I've typically not recommended this.

The issue of back focus have all been previously discussed: https://www.cloudyni...sis/?p=10230550 and https://www.cloudyni...sis/?p=10235330

There are solution to all these points.

With availability of the TRYBE Latch, a sound mechanical interface now exists for the use of a PVS-14 in configurations less known.

 

Also a great accessory for Afocal use. 
 

Hi Cnoct, 
Great mod !
Last year I've been able to modify PVS-14 for prime use too.
 
But there is an issue to focus it in telescopes.
The reason is the distance between the photocathode and the focal point of the telescope is huge. I measured it to 35mm.
So backfocus is a real issue and i don't know if there are a lot of telescopes that can allow this.
 
Also with your method can you rescrew the oem objective lens and switch from prime to afocal easily ?
 
Last but not least it requires additional tools to do the mod and would void the warranty as people will have to remove the intensifier tube to remove the inner ring that holds the lens.

Edited by cnoct, 02 May 2022 - 11:07 AM.

[cnoct]

And if you want to go directly T2 threads on a diagonal etc... Skip the 2" adapter and have at it.

[a__l]

In Newtonians there is no need to use a paracorr to reach focus with glass eyepiece. But with PVS-14 in prime i couldn't reach focus in any Newtonians I tried.

So I don't understand why you speak about the P2. I don't have any and never spoke about it in my previous posts.

P2 it's a necessary accessory for newtons faster than f/6. Including for glass eyepieces.

NV astronomy requires serious financial investments. The price of paraсorr-2 is incomparable with the price of commercial NV. So for those who have PVS-14 (and for those who don't yet!) it's a good alternative to existing commercial offerings. To use PVS-14 in two modes, afocal and prime focus.

 

And further. The warranty for PVS-14 usually does not cover
used item. This device is made in such a way that it breaks very rarely. Do not fill it with water with the lens removed and forget about the warranty.

Edited by a__l, 02 May 2022 - 05:04 PM.

[ButterFly]

Asteroid hunting and galaxies is probably where I would use this. Only eight years to go before the warranty expires. Plenty of time for a silvered secondary.

[slavicek]

P2 it's a necessary accessory for newtons faster than f/6. Including for glass eyepieces.

NV astronomy requires serious financial investments. The price of paraсorr-2 is incomparable with the price of commercial NV. So for those who have PVS-14 (and for those who don't yet!) it's a good alternative to existing commercial offerings. To use PVS-14 in two modes, afocal and prime focus.

 

And further. The warranty for PVS-14 usually does not cover
used item. This device is made in such a way that it breaks very rarely. Do not fill it with water with the lens removed and forget about the warranty.

I have f/3.3 and I do not use P2 with it - whether using ordinary eyepiece or using NV. I still have the P2 in it's original box.   But that is me (and I know others who do the as I do), however if you like to use P2 then use it. The point I want to argue is that it is not necessary to use P2 in "fast" DOBs, especially for observing the stuff one use NV for. 

I like doing Mods but this mod will definitely void the warranty, no question about that!

[GOLGO13]

I think the Paracorr depends on what you are observing. For nebula work I don't think it's a big deal. Plus it adds to an already fairly ridiculously tall stack (assuming 67mm afocal setup). For doing non-nebula work It's helpful depending on your setup. In some cases the edges of the view are already kind of messed up from the curvature of the envis lens (assuming). I've not done much 67mm on non-nebula targets yet.

 

Like for visual, It depends on the user as to if the Paracorr is necessary. I use it in my 10 inch F4.7 for visual. But I don't mind the view without it, especially if I'm focusing on small objects in the middle of the view.

 

Wide field views of the Milky way helps with some sort of coma correction.

[rfr66]

I have used my PVS-14 in prime. Per Cnoct's suggestion I had the internal and external retaining rings left out of my build by my dealer Nocturnality. This may have voided the manufacturer's warranty but my dealer is honoring the warranty directly. Now I just simply unscrew the objective lens and attach the prime adapter. It's very easy to switch back and forth quickly. I have had no problem with back focus issues. I am using it on my TEC 200FL f8 and changing focus from afocal to prime was only a small difference. I noticed that the contrast was better when viewing in prime and I stuck with it the whole night while viewing galaxies, globulars and planetaries. Using a barlow also worked well.  A 1.25" filter can be reversed mounted inside the Trybe latching mount which makes it very convenient. I highly recommend this solution to have your PVS-14 work in prime too. I will probably need to use afocal to view the larger nebulae but It's nice to have options.

[chemisted]

I have used my PVS-14 in prime. Per Cnoct's suggestion I had the internal and external retaining rings left out of my build by my dealer Nocturnality. This may have voided the manufacturer's warranty but my dealer is honoring the warranty directly. Now I just simply unscrew the objective lens and attach the prime adapter. It's very easy to switch back and forth quickly. I have had no problem with back focus issues. I am using it on my TEC 200FL f8 and changing focus from afocal to prime was only a small difference. I noticed that the contrast was better when viewing in prime and I stuck with it the whole night while viewing galaxies, globulars and planetaries. Using a barlow also worked well.  A 1.25" filter can be reversed mounted inside the Trybe latching mount which makes it very convenient. I highly recommend this solution to have your PVS-14 work in prime too. I will probably need to use afocal to view the larger nebulae but It's nice to have options.

What diagonal do you use in prime?

Edited by chemisted, 03 May 2022 - 09:00 AM.

[a__l]

I have f/3.3 and I do not use P2 with it - whether using ordinary eyepiece or using NV.

https://www.televue....art_updated.jpg

 

For your 22" Teeter at the edge of the field TV67 stars are about 200 airy radius. Why did you spend money on such a telescope? You do not need it.
You are from a relatively good mirror (I assume you have 1/2-1/3 lambda, you make a telescope with a surface accuracy of >50 lambdas - based on the airy radius) A rough glass plate will suffice for you instead of a parabolic mirror.

 

 

I think the Paracorr depends on what you are observing. For nebula work I don't think it's a big deal. 

Well, yes. At your of TV67 at f/3.3 edge, every more or less bright star will turn into a cometary nebula.

Edited by a__l, 03 May 2022 - 08:28 PM.

[a__l]

And in general, a rough estimate. Due to the coma for f/3.3, you will lose from a third to a half of the mirror diameter. Those the stars will be blured and the limited magnitude you will see will be correspondingly smaller.

 

Whether it's an NV or a glass eyepiece. This is the effect you get when P2 is in your box, instead of something in the telescope

 

I see Joko liked this, he probably likes this result

Edited by a__l, 03 May 2022 - 08:27 PM.

[a__l]

on my TEC 200FL f8 and changing focus from afocal to prime was only a small difference

There is probably something wrong here. Joko is right when he writes about 35mm.
Probably on your telescope Yuri installed a focuser something like 3.5″ draw tube travel. Newtons usually have 1.5" ....

 

https://www.televue....page.asp?id=214

 

See for TV55 parameter F 1.16" + 1" for TV67 (if I remember it right)

In this case, for prime, you need to move the focuser to the telescope lens (inside), for afocal, away from the lens (outside).

Edited by a__l, 03 May 2022 - 06:22 PM.

[rfr66]

What diagonal do you use in prime?

I’m using the T2 Baader Zeiss prism diagonal. I have the PVS-14 screwed right into it for a very short light path. 

[rfr66]

There is probably something wrong here. Joko is right when he writes about 35mm.
Probably on your telescope Yuri installed a focuser something like 3.5″ draw tube travel. Newtons usually have 1.5" ....

 

https://www.televue....page.asp?id=214

 

See for TV55 parameter F 1.16" + 1" for TV67 (if I remember it right)

In this case, for prime, you need to move the focuser to the telescope lens (inside), for afocal, away from the lens (outside).

The directions for focus seem correct. I’ll take an accurate measurement for focus travel next time. 

[a__l]

The directions for focus seem correct. 

I have decent experience with NV. Only my telescopes are different, 24" f/3.3 - now a deep modernization for carbon and 18" f/4 - modernization for carbon a couple of years ago ...

[slavicek]

https://www.televue....art_updated.jpg

 

For your 22" Teeter at the edge of the field TV67 stars are about 200 airy radius. Why did you spend money on such a telescope? You do not need it.

Well, I did not buy 22" telescope for NV only. That should be kind of obvious.

Anyway, back to the topic:

Afocal use of NV is usually "back focus" friendly. Converting PVS-14 to prime focus will have focusing issues with some telescopes. That is one of the drawbacks of this MOD. I guess there's always a trade off.

[a__l]

Well, I did not buy 22" telescope for NV only. 

OK. I will replace TV67 with Ethos 21. Let it be a little less than 200 radius. Basically, it doesn't change anything. Use the P2 and you will solve both the optical problems with your glass eyepieces and the possible problem of installing the prime PVS-14 in your telescope.
Although for the latter I would recommend buying two P2s, one for afocal and one for prime. Removing the P2 head in the dark is another problem. I use two coma correctors.

[GOLGO13]

I will check again, but it seemed to me that afocal edges won't be perfect because of the way it works. This was for sure the case with the TV40 Plossl. No real benefit with Paracorr. However, I've not done enough testing with the 67mm setup. I tried it once and didn't think it was needed, but I could do more checking.

For prime focus on non nebulas coma correction has potential. I've only done this with the MPCC and filter wheel.

Visual I've been on and off with the Paracorr. Not that I didn't like it, just on and off. I have one now and use it for visual. However, I'm more of a refractor guy most of the time. I like wide field observing in general.