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PVS-7 on the way!

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#26 Eddgie

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Posted 03 July 2020 - 08:38 AM

What are all the c mount lenses that will allow mod 3 binocular operation and most users to have a comfortable IPD? I think I’ve seen the 50mms work but how about higher focal lengths?

While it is not C mount, you can use CCD guide scopes.

 

The problem with any NV binocular used at prime focus is going to be the IPD of the wearer. This will generally limit you to 50mm objectives. This is because by the time you put the lens in a cell, then mount the cell in a tube, you are looking at a device that has an external diameter of about 58mm.  My own IPD is 64mm, so I have not found any 60mm optic that had a small enough external diameter to be useful as a binocular pair.

 

SLR lenses are generally even worse because they typically have a much bigger diameter than the objective and this is to facilitate the focuser and aperture rings. 

 

The longest focal length I have used in a full binocular is a pair of 50mm f/3.8 CCD guide scopes.   These are not C mount, but using a 1.25" nose on the pods, you can then utilize the 1.25" helical focuser interface on the CCD guider.

 

I did this a long time ago but the problem was that the play in the bridge made it hard to keep the tubes in perfect alignment.  I had given up on it because it was too hard to keep manually keep the tubes parallel while moving around the sky.

 

Here is the binocular with the pair of 50mm f/3.8 CCD finder scopes.  As you can see, the outside of the dew shields is almost touching.  

 

Mod 3 with 7x lenses.jpg

 

This was before I had a 3D printer though, and I am in the process of re-visiting this approach using the same approach as I used for the 3x binocular, which was to print a bridge for the lenses that will hold them in perfect alignment.  Even at 3x, I had some problem with the lenses not staying collimated. Some of this was due to the slop in the bridge on the Mod 3 and some of it was with the slip over connectors.  (I had the first Mod 3 binocular with C mount and after some discusssion with AB night vision about the slop, about a year later, they came out with an upgraded bridge.  Now it is better, but it still has some play.  Printing the bridge though was the real answer.  With a 3D printed bridge (the white thing in the picture) I have zero issue with lens collimation.

 

post-14923-0-44295300-1547953091.jpg

 

I am also looking at building a pair of lenses from a pair of 30mm f/4 guide scopes.  I have the 3x lenses, but it would be easier to go back and forth between the 30mm and the 50mm bridged lenses than go back and forth between the 3x afocal and 50mm guide scope lenses.  I could just slip the bridged lenses off of the 1.25" barrels, and swap them rather than have to re-mount the ENVIS lenses and move the filters. 

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Edited by Eddgie, 03 July 2020 - 09:11 AM.

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#27 Eddgie

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Posted 03 July 2020 - 08:48 AM

And the merits of the CCD Guide scopes as binocular lenses are that they are very light with a minimal number of elements and quite excellent transmission.  The only reason I gave up on them the first time was the issue with keeping them aligned. They did not really weigh any more than my 180mm Nikon lens and because there were two of them and it was true binocular summation, I think the views were better than using a single monocular with an f/2.8 lens.  Binocular summation is powerful stuff.

 

It is the 3D printer that made me want to go back to the CCD guide scope lenses. The bridge was fantastic on the afocal 2x lenses, completely solving the alignment issue. I don't know if I will actually do the 30mm pair, but I want to try the 50mm pair again for sure.

 

I have even considered building a binocular out of a pair of inexpensive 6" f/4 imagaing Newtonians.  It think that would be freaking awesome.



#28 joelin

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Posted 03 July 2020 - 01:17 PM

Thanks for sharing your experiences Eddgie. If possible, could you share the 3d adapter designs so others can also try this setup?

 

Meanwhile, I asked earlier, but wonder if a larger aperture telescope + 1x NVD would provide similar views as a 2x smaller aperture telescope as a binoscope + 2x NVD

 

Let's take the popular 150mm f/4 imaging newt. This would seem to have just over 2x the aperture as a single 102mm f/5 refractors. So the imaging newt vs the dual 102mm refractors is a good comparison.

 

They would also have similar image scales at 600mm focal length for the newt and 510mm focal length for the refractors. 

 

So given similar total aperture and similar image scales....would they product similar images?



#29 Solar storm

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Posted 04 July 2020 - 07:45 AM

How do you install a gain knob on a PVS7

I had it installed by Tom Lyons.  He’s a night vision guy in Texas.  Super nice guy.



#30 Eddgie

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Posted 04 July 2020 - 09:38 AM

Thanks for sharing your experiences Eddgie. If possible, could you share the 3d adapter designs so others can also try this setup?

 

Meanwhile, I asked earlier, but wonder if a larger aperture telescope + 1x NVD would provide similar views as a 2x smaller aperture telescope as a binoscope + 2x NVD

 

Let's take the popular 150mm f/4 imaging newt. This would seem to have just over 2x the aperture as a single 102mm f/5 refractors. So the imaging newt vs the dual 102mm refractors is a good comparison.

 

They would also have similar image scales at 600mm focal length for the newt and 510mm focal length for the refractors. 

 

So given similar total aperture and similar image scales....would they product similar images?

As to how these two kinds of scopes would compare, I really don't know.  I would guess that the binocular would be better, but that is just a guess.  I have no experience using my NV gear in a binocular telescope. 

 

Sadly, due to some operating system curruption, I had to reload my system a long time ago and lost the bridge 360 Fusion design file.   The bridge was set for 64mm IPD, so unless your IPD were 64mm, you would need to modify it anyway so you would need the Fusion file.  So, don't have it.  So sorry.   

 

If you have Fusion 360, it is a pretty easy design to make. 

 

I just ordered a new pair of the 50mm CCD Guide Scopes, so when they get here, I will be designing a new bridge for them. 



#31 joelin

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Posted 04 July 2020 - 01:39 PM

I did some thinking about binoviewers and 2x NVDs and its still not clear to me why they're worse than a single NVD. 

 

I use binoviewers with 2x glass eyepieces in my SCT and find the amount of detail I can discern to be roughly the same as the 1x eyepiece + diagonal situation. The reason is although yes the light is split in half along each path of the binoviewer, and the resulting view a single eyepiece is dimmer, the brain will combine the two dim images from two glass eyepieces and create a brigther image that will be roughly the same as a 1x eyepiece in a diagonal.

 

It seems like this is not the case for 2x NVDs and binoviewers. If it translates over for glass, why not NVDs?



#32 Eddgie

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Posted 04 July 2020 - 02:19 PM

 the brain will combine the two dim images from two glass eyepieces and create a brigther image that will be roughly the same as a 1x eyepiece

 

That is not really the case. Ignoring transmission losses, each eye will receive a view that is 50% as bright, but binocular summation does not add those together to give you an image that is perceived to be a bright as you would get with a single eyepiece.  Binocular summation will add the images together, but it is not 100% effective.  The total perceived brightness will be about the same as using an aperture that is .7 diameters of a single eyepiece.  So, if you use a binoviwer in a 100mm scope, for the same exit pupils, the view will be as bright as the view in a 70mm scope used with a single eyepiece. 

 

Next is the effect of the vignetting because of long light path. This is the golden rule for calculating vignetting.. A light cone passing through a circular restriction will be reduced by 1mm in diameter for every multiple of the focal length of the telescope from the point where it passes through the restriction to the focal plane.

 

Suppose your binoviewer has a 26mm front aperture and a light path length of 115mm.   The light path of the Mod 3 is about 18mm, so from the front aperture of the binoviewer to the photocathode, the light would travel 133mm. Using the golden rule, if the telescope was f/6, then a fully illuminated light cone entering into that 26mm hole would travel 133mm to the photocathode and in that distance the diameter of that cone would be reduced by (133 / 6 = ) 22.16mm. This means that by the time the fully illuminated circle reaches the focal plane, only a 3.84mm circle is fully illuminated, and outside of that, the field is vignetted and the vignetting is quite pronounced. Another way of saying this is that only a 3.84mm circle at the center of the field is working at full aperture, and outside of this circle, the aperture is smoothly reduced until you get to the edge of the photocatode.  Now even though you can see the vignetting, a small subject placed at the center of the field would be seen at full brightness.

 

As can be seen though, the dimming and vignetting are very negative consequences and in most cases, you really can't use a focal ratio faster than about f/6.  At f/5, even the center of the field would not be fully illuminated using a binoviewer with the specs I used in the above axample. 

 

That should not stop you from doing it if you like but this is what happens.


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#33 Eddgie

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Posted 04 July 2020 - 02:30 PM

And Edz posted a lot of papers about binocular summation in the binoviewer forum a long time ago, but some of the links to the papers that contain that data are now dead, but the .7 effective aperture brightness came from a paper he linked.  So, you don't get all of the brightness back, but you do get some, though the photocathodes themselves are only stimulated with half the number of photons each, so from a signal to noise ratio perspective, it is like each photocathode is working at twice the focal ratio, and while binocular summation might improve that by 1.3x, it will be noisier than a single device will be.

 

Again, none of this should stop you from trying it though.  I tried it a few times and I did not think it was as good as using a single eyepiece but I can point to a lot of things over the years that I did not think worked well, but that others did, so mostly I am trying to focus here on how a specific configuration would behave.  I can tell you what it does and why it does it, but I cannot tell you if that would cause it to be below your threshold for acceptance.  For that, you would have to try it yourself. 

 

Using the above examples, you could calculate the fully illuminated circle for a given configuration if you have the light path figures. I can't even tell at what point vignetting would become a problem for anyone but my own preference is to use configurations with as large a fully illuminated image circle as possible and I have  little tolerance for vignetting.  


Edited by Eddgie, 04 July 2020 - 02:40 PM.


#34 joelin

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Posted 04 July 2020 - 02:37 PM

I'm also not sure about the "each photocathode is working at twice the focal ratio".

 

If I have an f/4 camera lens and only allow half as much light to come in (such as creating a mask to block 50% of the front objective), the equivalent aperture is now f/5.6. I know this because I can double the exposure time at f/5.6 and get roughly the same brightness image as f/4. 

 

If I go all the way to f/8, I need to quadruple the exposure time. 


Edited by joelin, 04 July 2020 - 02:38 PM.


#35 Eddgie

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Posted 04 July 2020 - 03:37 PM

I'm also not sure about the "each photocathode is working at twice the focal ratio".

 

If I have an f/4 camera lens and only allow half as much light to come in (such as creating a mask to block 50% of the front objective), the equivalent aperture is now f/5.6. I know this because I can double the exposure time at f/5.6 and get roughly the same brightness image as f/4. 

 

If I go all the way to f/8, I need to quadruple the exposure time. 

I am sorry, you are correct. It is like changing the brightness by one full f/stop. 


Edited by Eddgie, 04 July 2020 - 03:40 PM.


#36 joelin

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Posted 04 July 2020 - 03:40 PM

And Edz posted a lot of papers about binocular summation in the binoviewer forum a long time ago, but some of the links to the papers that contain that data are now dead, but the .7 effective aperture brightness came from a paper he linked.  So, you don't get all of the brightness back, but you do get some, though the photocathodes themselves are only stimulated with half the number of photons each, so from a signal to noise ratio perspective, it is like each photocathode is working at twice the focal ratio, and while binocular summation might improve that by 1.3x, it will be noisier than a single device will be.

 

Again, none of this should stop you from trying it though.  I tried it a few times and I did not think it was as good as using a single eyepiece but I can point to a lot of things over the years that I did not think worked well, but that others did, so mostly I am trying to focus here on how a specific configuration would behave.  I can tell you what it does and why it does it, but I cannot tell you if that would cause it to be below your threshold for acceptance.  For that, you would have to try it yourself. 

 

Using the above examples, you could calculate the fully illuminated circle for a given configuration if you have the light path figures. I can't even tell at what point vignetting would become a problem for anyone but my own preference is to use configurations with as large a fully illuminated image circle as possible and I have  little tolerance for vignetting.  

so based on what you're saying here...its not a good idea to do binoviewers with 2x glass eyepieces either (no NVDs)...as I'll just get 0.7 effective aperture

 

so if thats the case...people use binoviewers for comfort and not for detecting extremely faint objects?


Edited by joelin, 04 July 2020 - 03:40 PM.


#37 Eddgie

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Posted 04 July 2020 - 04:09 PM

Well, people use binoviewers for a variety of reasons.  but yes, when you use a binoviewer, even with binocular summation, for a given exit pupil, an extended object will only appear as bright as it would in an aperture of .7 times the diameter used with monocular vision.

 

Limiting magnitude is reduced by about .2 or .3.

 

To compensate for this on extended objects you can simply use a slightly lower power to offset the dimming and while this reduces the image scale slightly, binocular summation makes things look larger than they do to one eye, and it enhances the visual acuity, so using a slightly lower power in practice is not much of a penalty.  This does not help with point sources though. For that, you loose about .2 or .3 magnitudes, but this is not really easy to see unless one is doing very careful limiting magnitude comparisons.   The is somewhat less than it is with seeing something with direct vision vs averted vision.  In any given field, a .2 or .3 difference in limiting magnitude is not going to be something that jumps out.

 

And I would not say that people should not use them.  Before I went to night vision astronomy I used binoviewers exclusively for all observing.  I still use them for all solar system observing.  

 

In addition to improving visual acuity, they also provide a more relaxing view, and the give a spacial depth that is not really present when monoviewing.  While a binoviewer does not have true parallax and therefor does not allow depth perception, when viewing with them, most people will report that the fields appear more 3D like.  We know that it is not truly 3D, that it is just a trick of the brain, but many binoviewer users will tell you that they think the binocular field of view seems more immersive.  


Edited by Eddgie, 04 July 2020 - 04:14 PM.


#38 Dale Eason

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Posted 04 July 2020 - 04:11 PM

I use bino viewers for more detail than I get with a single eyepiece. For what ever reason it helps to see more detail when the object is bright enough.   Bino however dims the object I'm looking at and if it was very dim in one eyepiece it will be too dim to see at all in the bino viewer.  So I only use the bino views on Bright enough objects.  When I'm looking for dim fuzzies I don't use the bino viewers.  I use a single eyepiece.

 

But when usable it is not just for comfort.  There is actually more information observed.

 

Dale


Edited by Dale Eason, 04 July 2020 - 04:12 PM.


#39 StarAlert

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Posted 05 July 2020 - 03:27 PM

I gave up on PVS-7s a few years ago because it was almost impossible to find one with a really high quality tube.  As much as I like using both eyes at the telescope, every PVS-7 I have owned simply had too much noise for my liking.  

 

I remember being out at Mansfield dam a few years ago with my last PVS-7 and comparing the view with my Micro with F9800 tube. I could see Barnard's loop easily and brightly in my a single Mod 3 but when I used the PVS-7, while I could see the loop pretty easily, the view was extremely grainy.   Now without narrow pass filters at 1x, I thought the standard PVS-7 did a really nice job, but when used in my 12" F/4.9 with a long pass filter on galaxies, the noise was just a bit to much to give really enjoyable views of galaxies.  

Now two or three years ago (time flies!) there was a small lot of PVS-7s sold with filmless white phosphor tubes.  At the time, I was on the fence about it so I tarried on getting one.

 

One night Peter and I went to Mansfield dam (after he had sorted his PVS-7 out. It was purchased in a PVS-7 A housing that had a lot of issues and he rehoused it into a PVS-7 B/D) and had some time to use the re-housed PVS-7.   It was wonderful. I was really impressed with the view. It was the first time that I had ever used a PVS-7 that fully pleased me.   The view was crisp and bright, and very quiet. 

 

Time goes buy and I was PMed by a CN member yesterday that had bought one of these when they became avialable, and he was wanting to know if the price was fair.  Now at the time, I did not realize it was one of the filmless tube PVS-7s.  He had provided a spec for the SN of 24.1 or something and I thought it was a thin film tube so I was not so interested, but I did know someone that was looking for a PVS-7 and forwarded on to the other individual.  

During the email, the other individual pointed out that the SN was actually over 30.  There had been a copy of the spec sheet in seller's original PM, but as it turns out, he had apparently transposed the minimum SN date in the text of his note (with the other figures like .3 EBI and such) and when I went back to look at the spec sheet, I realized it was one of the L3 filmless tubes.  

 

Since I had already pointed the other buyer to it, I did not fell like I should go steal the sale from him, but I told the seller if the other buyer passed, I would take it.  About 18 hours later, one of the unicorn filmless WP Unicorn PVS-7s is on its way to me.  How fun for me!

 

One of the biggest problems with a full NV binocular is that it is very hard to get more than 3x and a zoom lens is of course not really possible.  I think this unit will pair really well with my 70mm to 210mm zoom. I also really look forward to using it in my 12" dob and with the zoom lens.  I mostly run with full gain, so for me, the absence of a gain control is not really that important. 

 

Some thoughts  on binocular summation as it applies to the PVS-7 and full binocular... 

 

A Mod 3 (or other binocular) has two image intensifiers and the random scintillation and noise patterns are different, so the brain kind of averages these artifacts out of the view all by itself, and with a full binocular, I do believe you get a very meaningful boost in perceived signal to noise ratio.  There is nothing like using a full  binocular.

 

The PVS-7 though uses a single tube, and both eyes see the exact same pattern, and because if this, I don't feel like one gets the same perceived signal to noise ratio benefit that is provided by a full binocular. I do believe that there is some slight improvement, but my subjective opinion is that it is not nearly the same as using a full binocular.

 

The brightness penalty of a standard binoviewer is not present in a PVS-7.  The output brightness of a PVS-7 would not be any different from two single monoculars because the tube itself is set up to provide a minimum luminous output to each eyepiece so there is no real penalty here.

 

The last attribute of binocular summation is visual acuity.  Just like with a standard binoviewer, the PVS-7 allows the users to use both eyes and just like with a standard binoviewer, the image will look larger than it would using one eye, and the visual acuity will be improved.  This is independent of the SN issue because while there is only one image shared by both eyes, this is analogous to getting an eye exam and viewing a single visual acuity chart at a distance with one eye, then the other eye, then opening both eyes and noting an improvement in the sharpness of the letters on the vision test chart.  

 

I am very happy to have the good fortune to get one of these unicorn PVS-7s.  I have often wondered if I could find one, if it could or would displace a monocular as my primary telescope observation device.  This unit does not have the SN of my best monocular, but it is very similar in specs to my first filmless tubes in my original Mod 3 binocular, and that worked quite well for years for me in my telescope as far as performance goes, so I am looking forward to seeing if the improved visual acuity and low EBI offsets the better SN of my best monoclar. 

It was a real surprise to me to see one of these become available.  I thought having pointed it to another CN member, it would escape me, but the Matrix must have wanted me to have it.

 

Weather his is not great with more dust expected in coming days, but the first chance I get, I will give some A/B comparisons in the telescope. 

 

Hope you are all doing everything you can to stay safe. Remember, it is very dangerous out there. I appears that a lot of people out there may not be that interested in protecting you, so protect yourself. 

Eddgie,

I’ve been looking for a PVS-7 with WP. How does this compare to the L3 you are referencing?

https://www.nightvis...e-phosphor.aspx



#40 joelin

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Posted 05 July 2020 - 03:30 PM

It definitely seems like there demand for PVS-7 WP and also potentially with gain.

Who was the original person who made them and what would it take to have them make a few more?


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#41 StarAlert

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Posted 05 July 2020 - 04:01 PM

And here is an L3 filmless WP tube that is compatible with a PVS-7. 
https://www.ultimate...e-c001-1601.htm

 

Can this just be dropped into any PVS-7? 



#42 Eddgie

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Posted 05 July 2020 - 04:55 PM

And here is an L3 filmless WP tube that is compatible with a PVS-7. 
https://www.ultimate...e-c001-1601.htm

 

Can this just be dropped into any PVS-7? 

While they show this on their web page, to the best of my knowledge, they have never had one in stock.

 

The 10130 format tube is indeed a drop in for the PVS-7.  It was designed specifically for the PVS-7 and only works in goggles like the PVS-7.  

 

There are notable differences between these tubes in terms of physical packaging and internal design. Physically, they are the same diameter but a different length.  They do not use pigtails for the connection to the power supply, instead using pin sockets on one end of the tube to get power.   There are no external gain control wires.

 

The other difference is that the fiber optic bundle of the 10130 type tube does not have the twist (non-inverting) that is present in the PVS-14. In the PVS-7, the image is inverted by the collimator I think but because the PVS-14 does not have a collimator, the fiber bundle has to be twisted so that the upside down image at the photocathode is turned right side up at the output window.  

 

Anyway, I have been dealing with Ultimate for four years and they know that I was looking for a high end PVS-7 tube, but my phone never rang.   Why they have it on their page, I do not know.


Edited by Eddgie, 05 July 2020 - 05:02 PM.


#43 Doug Culbertson

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Posted 05 July 2020 - 05:33 PM

It definitely seems like there demand for PVS-7 WP and also potentially with gain.

Who was the original person who made them and what would it take to have them make a few more?


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This place claims to have WP PVS-7s in stock. Just a bit more expensive than the ones that Glynn was selling awhile back. 



#44 Eddgie

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Posted 05 July 2020 - 05:54 PM

This place claims to have WP PVS-7s in stock. Just a bit more expensive than the ones that Glynn was selling awhile back. 

They might have them in stock, but these are Harris tubes (and not that this is at all bad, the thin film tubes are very nice tubes) but the Harris tube P45 tubes that NV Devices had in stock had minimums that were much lower than the F9800VG.  Now that does not mean the specs might not have been higher than minimum but they were unlikely to have been in even the SN of 28 range.   

 

And that is why I never bought one.  For me, the biggest objection to the PVS-7 was simply that it was very difficult to find a tube that would match the specs of the filmless monocular tubes (or even the excellent F9800VG monocular tube for that matter.. I never owned a PVS-7 that came close to performing even as good as my F9800VG.)

 

pvs  7 specs.jpg

But if they have them in stock and the SN is in the 30s with PCR in the 2200 range and gain in the 60K range, then maybe for someone that wants to use both eyes, it would be worth it??? 

 

These would have spec sheets so I would assume that if someone called them, they could tell what the specs were. 


Edited by Eddgie, 05 July 2020 - 05:57 PM.

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#45 Eddgie

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Posted 05 July 2020 - 06:01 PM

And my interactions with NV 4 Less is that they are motivated deal makers.  I would guess that their stated price is just a "suggested" retail price and that some negotiation would probably shave $500 off of that price. Maybe more.   Wholesale on that tube is probably $2700 or something.   After all, the F9810 is just a thin film tube and not known as a blazing performer.  


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#46 StarAlert

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Posted 05 July 2020 - 06:19 PM

If I picked one of these up, it would need to be modified to put in a scope, right? 



#47 joelin

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Posted 05 July 2020 - 06:32 PM

They might have them in stock, but these are Harris tubes (and not that this is at all bad, the thin film tubes are very nice tubes) but the Harris tube P45 tubes that NV Devices had in stock had minimums that were much lower than the F9800VG. Now that does not mean the specs might not have been higher than minimum but they were unlikely to have been in even the SN of 28 range.

And that is why I never bought one. For me, the biggest objection to the PVS-7 was simply that it was very difficult to find a tube that would match the specs of the filmless monocular tubes (or even the excellent F9800VG monocular tube for that matter.. I never owned a PVS-7 that came close to performing even as good as my F9800VG.)

attachicon.gifpvs 7 specs.jpg
But if they have them in stock and the SN is in the 30s with PCR in the 2200 range and gain in the 60K range, then maybe for someone that wants to use both eyes, it would be worth it???

These would have spec sheets so I would assume that if someone called them, they could tell what the specs were.

curious to know how you know they're Harris tubes ...it doesn't seem obvious from the listing

this goes to an even bigger question..that often I see online people selling PVS-14 gen 3 with nothing that indicates if its L3, film or filmless, specs, or Harris or whatever....

how is anyone supposed to know since these seem to be big impacts on performance?

as an example...here is a mystery PVS-14: https://www.ebay.com...ksAAOSwTeNfAiLd

another mystery PVS-14: https://www.atncorp....ision-monocular

both of those don't say much in terms of the specs or if its film or filmless and are quite expensive....
do people just by them without any idea if its low, medium or high performance???

Wouldn’t that be like buying a computer without knowing the specs?

Edited by joelin, 05 July 2020 - 06:43 PM.


#48 Eddgie

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Posted 05 July 2020 - 07:22 PM

curious to know how you know they're Harris tubes ...it doesn't seem obvious from the listing

this goes to an even bigger question..that often I see online people selling PVS-14 gen 3 with nothing that indicates if its L3, film or filmless, specs, or Harris or whatever....

how is anyone supposed to know since these seem to be big impacts on performance?

as an example...here is a mystery PVS-14: https://www.ebay.com...ksAAOSwTeNfAiLd

another mystery PVS-14: https://www.atncorp....ision-monocular

both of those don't say much in terms of the specs or if its film or filmless and are quite expensive....
do people just by them without any idea if its low, medium or high performance???

Wouldn’t that be like buying a computer without knowing the specs?

Second line in the description on the ad:

 

 

Image Intensifier Tube Type: ITT Exelis/Harris  Autogated Hand Select WHITE PHOSPHOR

One should never buy from an ad that does not give a tube model.   

Some dealers used to go by arbitrary grade such as "Silver/Gold/Platinum" or "Alpha/Bravo/Charlie" but of course the problem with this is one dealer's Platinum tube might be another dealers Gold tube, so buying by grade this way, you really don't know what you are getting.

Contrast this to NVDevices, which generally sells by model number (F9800YG or F9800VG or whatever) and for the model number, they would publish Harris's minimum specs for that model.  The exception being the ULT, which was a house grade where they had indeed selected the very highest performance tubes and posted the minimums for a tube with that grade.

 

Otherwise, if they don't advertise a specific model number, you really don't know what you are getting unless it is a Harris or L3 tube model number, in which case it would probably come with a spec sheet anyway.

 

But we know the tube in the PVS-7 is a Harris F9810 because they say it is a Harris tube right in the description, and the only real spec they give is the SN, which is shared by the F9810VG, YG, and UG, but they don't even say that so you don't know the PCR minimum.




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