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New Mod 3 Binocular Report

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#1 Eddgie

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Posted 19 January 2020 - 02:09 PM

I recently acquired a second night vision binocular.  I did not mean for it to work out this way.. The Matrix made this happen.  

 

My road map was to wind up with a really top end monocular for telescope viewing, where I think the performance of the monocular is most important, and a dedicated binocular for low power work.  Since a binocular is really mostly only usable for 1x and 3x due to IPD restrictions making SLR lenses just not a practical configuration option, the plan was to put together two F9800VG tubes in Mod 3 bodies with PVS-14 objectives. Since they would be used exclusively for binocular viewing or as two monoculars and not ever be called on to work in a telescope and because I like the fast focusing of the PVS-14 objective (infinity to about 10 inches in less than half a turn vs the multiple turns required to do the same with the ENVIS).

The plan was to take the F9800VG from my Micro and supplement it with another F9800VG.

With this plan, I would use the power supplies from the original Mod 3 pods and sell them to finance the new high spec Mod 3 monocular.

 

Now along the way, Ed Wilcox put a Mod 3 with a pair of MX11769 Omni VII tubes up for auction and impulsively, I entered a bid.  It was a dumb bass thing to do, but I did it.  I entered the minimum bid and imedtially somewhat regretted it, but a bid is a bid, and while you can retract a bid on eBay, they don't like when you do that, and stupidity to me is not a valid reason to retract a bid.

 

Of course I had the hope since I made the minimum bid, I would be outbid by someone but again, the will of the Matrix is often what determines the outcome of these things and even though I made the minimum bid, about four days later, I was the proud owner of a complete new Mod 3 Brovo binocular.

 

The specs on the tubes were listed as Omni VII. Now most people say that an Omni VII tube will have a minimum spec of 28 SN, but I am not so sure this is correct so I was skeptical of this particlar spec, but Ed has a tester and the bench test showed the resolution of these tubes as 68 lines and that is pretty good for a thin film tube.

 

In a message I asked Ed if he had an idea on the EBI and since these where old spec contract tubes, no specs would be included with the tube, but Ed said that he thought that on is scale of EBI, they were an 8, with 10 being best, and he reckoned the EBI to be maybe .8 which again, is pretty good for thin film tubes. 

 

So, a week later, the binocular comes to me. It is packed in a new Pelican case (nice) and includes some accessories, so a pretty complete kit.

 

Ok, first time I turned them on  ----- Noise.  Lots of noise ----. Now I have an F9800VG which absolutely has a minimum SN of 28, and these did not see that quiet. 

 

I spoke to Ed about it, and Ed said that he routinely raises the gain on these tubes because a lot of his customers want the gain as high as he can safely do it, with the understanding that this is almost for sure going to decrease tube life.   Ed said though that if I wanted him to lower the gain, which would lower the noise, he could turn down the gain limit, or he said that I could simply just lower the manual gain.  

 

So, I decided to reserve judgement on the gain until I had a really good night to use the tubes.

 

Meanwhile, it was time to cheap EBI.  In my sophisticated and top secret test facility which is cleverly disguised as a master bedroom closet, I proceeded to test EBI.

 

Now I do not have a test set.  I have to rely on comparing to tubes where I have a documented EBI and I have to give a somewhat subjective rating based on how much less or more clarity this or that tube has vs a tube with known EBI.

 

Now in my case, I had three tubes with known EBI.  The first tube has an EBI of .1, the second has an EBI of .2, and the final one, my newest high spec tube, as an EBI of .5.  Now .5 is actually (in my opinion) a really low EBI in terms of law of averages (and this is just based on the large number of L3 tube specs I have seen) but of course .1 is pixie dust stuff and .2 is minor magic.  .5 though is nothing to sneeze at. 

 

It is the characteristic of EBI to impart a veiling glow across the field of view and as the device gets to its threshold of performance, this veiling glow starts to obscure low contrast detail and as the EBI level increases, the amount of contrast needed to see a detail is increased.

 

Now the next thing is that with the gain on the new Mod 3 set to max, I have to say that it was shocking at how bright the view was in anything slightly above the threshold. The noise was crazy bad, but noise is noise and amplification is amplification, and even my highest performance thin film tube did not produce as much usable brigtness as the new Binocular. I can see why his customers want the gain turned way up, but this was a crazy amount of noise.

 

So, before the test, to make it a fair test, I used the manual gain control to adjust the overall brightness to about the same level as the new L3 tube, though these were both brighter than the very low EBI tubes, which do not have as sensitive PCR and have less gain. I don't know if that is why they were dimmer, but at the theshold, the new L3 tube was brighter, and I adjusted the gain on the new thin film binocular to match the brightness of the new L3 tube.

 

Next, I compared each monocular (I actually demounted the thin film tubes for this test) side by side with one another using the same eye and this was the way it worked out.

 

The .1 EBI tube is unmistakable even from the .2 EBI tube, though here, the difference is subtle. The clarity of a .1 EBI tube is quite amazing.  Now the noise (scintillation) was about the same as the .2 EBI tube, but at .1 EBI, there is a pretty crazy amount of contrast. 

The .2 EBI tube was also very clear but one could see under careful scrutiny that the black levels were not quite as black so that two black shoes could have clear outlines against the dark of the background in the .1 EBI tube, while in the .2 EBI tube, they were not quite as defined.

 

The surprise of the test was the left side thin film tube.  This tube is the nosiest tube in terms of scintillation, but in terms of EBI, it was surprisingly close to the .1 and .2 EBI tubes.   It took a comparison to the new .5 EBI tube to really make a judgment, but I would say that the EBI of this tube is among the lowest I have owned, coming in a bit closer to the .5 EBI tube than the .2 EBI tube, so probably around .4.  This was without a doubt, the lowest EBI I have ever seen in a thin film tube.  I was pretty floored and very excited about that.  Now this was with the gain turned down but still the image was as bright as it was in the L3 tube and I felt that overall, except for the scintillation, the tube was also probably graced with a pretty good PCR and gain.  Noisy though. 

 

Next the .5 flimless tube.  Without something to compare directly too, this tube would be quite excellent in terms of EBI, but with the baseline set at .1, .5 is blatantly obvious.  While most of the detail can be seen in this tube, dark on dark is harder to pic out than the other three tubes, but it makes up for a lot of this by having almost no scintillation and a very bright image. Still, it is a fine tube and except for the EBI spec, a great performer.  By comparison, the F9800VG tubes have as good a PCR and better gain, but tend to have somewhat higher EBI.  Nothing produces stars as sharp as those I have seen in the F9800VG though.

Last tube was the right side thin film tube, and even here, this was one of the better thin film tubes I have used.  Ed said he thought EBI was maybe .8, and I would say that this was about right!  This was the second nosiest tube though and while the EBI is still very good, the noise was still quite bothersome.  It still produced a clarity that was well past what I have ever seen in any PVS-7 tube I have owned (and that has been a shocking number) and once again, better than I had hoped.    From an EBI standpoint though, they are mismatched and I could actually see that when I tested them as a binocular. My left eye sees a view that is slightly clearer than my right eye sees and it is actually kind of easy to see and a bit bothersome but this is only really a factor when you are at extinction level so now on to the actual sky testing. Still, I can guess that it is more important to match tubes in binocular than I had thought. I figured you could fix all problems with gain control, but I have seen now that it could be slightly bothersome to have two tubes that were mismatched in EBI and SN. 

 

Under the sky, the mismatch of EBI is impossible to see. There simply is not the amount of contrast variation to make these small differences easily visible. Seeing a rack of shoes in a closet is a rich environment by comparison to the open sky. 

 

So, under the city sky, with the gain all the way up, the noise is hard to see when running long pass filters but with narrow filters, these tubes get pretty noisy.  Ah, but they are quite good at showing nebula! The PCR and gain here has to be really good because nebula were really bright!  Could some of this be due to the P43????   I don't know, but over the last couple of years, more and more, I have come to prefer P43, and that was another reason why I thought I would be content with a pair of thin film binoculars for low power sweeping.

 

Under darker skies, the noise does show more, so the gain has to be down even more, but still the image is quite bright.  Not as bright as the new L3 tube if I turn down the gain to tame the noise, but still as bright as the low EBI tubes. 

 

I love stars field in the thin film green tubes.  Stars just seem to have more dynamic range. They just pop out more!

 

Better than the filmless low EBI binoculars?  Wow, this is tough. The low EBI binoculars give a clarity that is difficult to match.  These come as close to looking at black and white photograph in front of your face as you can imagine.  While the thin film binocular has crazy gain, to use that gain means crazy noise, and in almost every situation, the filmless binocular not only has better clarity, but also a quieter noise level.

And what about the high spec tube?  It gets slaughtered by the binocular because the binocular gives full binocular summation, and until you have used a full binocular, it is hard to really appreciate how binocular summation elevates the view.  The noise seems less, and the brain sums the signal to increase brightness of any detail in the view.  If I were only going to do l low power with a binocular, I would take either of these binoculars over the high spec monocular.   

 

So, my original intention was to sell off the two filmless monoculars to recover some of the money I would spend on the new high spec monocular, but now I find myself unable to part with the original Mod 3 with C mount.  In spite of the fact that the tubes are otherwise nothing special, they still give level of clarity in low light that is quite remarkable.   For stellar work, I adore the thin film tubes because of the dynamic range of the stars.

In the 6" f/4 scope, the new monocular was sublime, with layered detail on nebula that was some of the best I have seen, but it was a cold night so the already low EBI was probably down in the neighborhood of the low EBI tubes, but in the summer, I expect that to change. 

 

Now I am not an expert on NV, and the reasons for some of the things I observed were just my own understanding of the way things work, and I could be wrong in some of my reasoning, but the actual observations are relative to the way I described them. 

For a lot of people, having this much money tied up in a pair of binoculars would seem to be insanity, but I have had a lot of eye issues in the last five years and as a result, I have come to feel like what precious little high acuity observing time I have left is going to be utilized using the gear I enjoy best, and each of these devices seems to do something that pleases me better than the other two, so for now, I want to keep them all and enjoy them to my fullest ability.

 

Hope someone out there that read this enjoyed it.

 

XQE_0001.JPG

 

Have an epic day, skywalkers! 


Edited by Eddgie, 19 January 2020 - 11:44 PM.

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#2 SiriusLooker

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Posted 19 January 2020 - 03:54 PM

Eddgie..

 As usual most impressive (detail), review.  Funny, unknown to me, prior to see this recent topic, I just sent you a private message, in regards to EBI. So this answer a couple of questions I was asking already. True this type of hobby can get very expensive at times, but the outcome can be just as rewarding, and are truly hard to convene what the mind sees in the dark.

I am curious does the Photo sensitivity have a factor in this as well, or is that the same as the gain increase?

Dennis



#3 Eddgie

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Posted 19 January 2020 - 07:51 PM

I have to confess that I do not know if PCR influences gain but logic would suggest that the more sensitive the photocatode, for a given number of photon strikes, more electrons would be introduced into the amplification process. 

But I am unclear on how the relationship works. 

 

In general though, for the three tubes I have spec sheets for, the one with the lowest PCR has the lowest gaih (62685/15500) with the next tube having a PCR of 2163 and gain figures of 63945/15500, and the highest PCR tube having 2727, with gains of 68026/16952.   So I do not really know for sure, but in this case, the higher PCR response tubes have higher gain figures but that could just be totally coincidental.

 

Now the lowest EBI tube is the middle one and not the lowest PCR tube.

 

Contrast these to my first F9800 though, and here the gain was almost 68,600/17700 with a PCR response of 2505 or something like that.  

 

So, my ignorance in this area is pretty evident.  I think PCR plays a role, but the internal amplification potential of the tube has to count too because as shown above, we have a thin film tube with a less sensitive photocatode that still has higher gain than my best filmless tube (though higher EBI and lower SN with the SN being meaningfully lower). And I think this is where my left binocular tube is at.  Again, Ed has the gain limit turned up very high so that makes it hard to really do a direct compare, but I believe that this tube has perhaps the highest gain I have ever had.  Turned to the same brightness though it is noisier by a good bit.  The EBI though was surprisingly low. I had expected something like 1 or even higher, but both of the binocular tubes had reasonably low EBI as compared to the tubes I have and the unscientific method used.

When you know how to look at EBI it is easy to pick out a low or high EBI tube, and if you have documented tubes to work from, I think it is feasible to give a decently close approximation of the EBI level. 

 

EBI is a very important tube spec, but I would not throw a lot of gain or SN out of the window to pick up a decimal place or two of EBI.  Now if the difference is between .2 or .3 EBI and .9 or 1 EBI, then yeah, that is enough to accept a lower PCR and gain figures.  But taking a low sensitivity tube with low gain to get a couple of decimal places of EBI is maybe a bad tradloff.

 

Most tubes I see people buying are reasonably balanced in that they are not the best in every spec, but no spec seems to be so low as to be concerned about getting satisfying performance. I don't really even know if my new tube was all that much of an improvement over my previous tubes, but it was a bit better in PCR and gain without sacrificing too much EBI, and that was what I was looking for.  I would not have gotten if if the EBI had been .9 or whatever. I asked Richard for PCR above 2500 with gain in the 680000 to 70,000 range, but I said EBI of .5 was what I was kind of hoping for, though I might have taken .6 if the other specs were super high.

 

SN Is not a big driver for me and I also made this clear to Richard.   While the SN of the new tube is not terrible (34.4) I considered EBI to be more important than having the highest possible SN. I have seen a couple of tubes out there with similar or better SN, PCR and gain specs, but with somewhat higher EBI as well. I had one guy tell me he had a 38 SN tube but the EBI was 1.1.  He was thrilled with the tube because it had high SN, but having had very low EBI tubes, I could not have made that trade. At the threshold, 1.1 is a lot of EBI vs .5   That would have been more EBI than I personally could have accepted in a brand new device. 

 

It is always a tradeoff.  The perfect tube may exist, but it is probably in the cockpit of an F22 or on the helmet of a Navy Seal. 

 

I wish there was not so much specmanship around tube selection, but considering we pay more for these things than some high end stereo gear, if one has the patience to wait for the tube that balances out the way the buyer is hoping, then since the cost is the same, then why not?  Is my tube the best tube?  LOL..No, I am positive that there are better tubes out there!  Is it good enough?  Well, unless some revolution occurs, I don't see myself trying to squeeze up from here.  Past where I am, the gains get slimmer and slimmer.  

 

I came to think it would be a mistake to sell the filmless Mod 3 C binocular (I was going to sell them as monoculars).  These tubes are unremarkable in every other way, but at the very threshold of observing conditions, like trying to see the nebula that M29 sits inside of, on a hot summer night, I might want to unplug that tube from the binocular and use it. The SN is not that great, the PCR is not that hot, and the gain is nothing special, but you don't see a .1 EBI or .2 EBI tube everyday and I decided it would be reckless to sell them off.  So, now I am stuck with two binoculars and a monocular.  Life is so cruel.  I really did not intend it to turn out this way, but the Matrix seems to think that this was what I was supposed to have. 


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#4 chemisted

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Posted 20 January 2020 - 09:31 AM

Eddgie has done a remarkable job of not just buying and evaluating a lot of different intensifiers but also taking the time to summarize his observations for others to digest.  I couldn't agree more with his conclusions regarding the weighing the importance of different parameters.  I have felt that if a person is going to pay the high price required for the very best tube out there then there needs to be some way to quantify that decision.  I also feel this quantification can be useful when buying used or at a better price point than the very top end.  Eddgie's conclusion that his very low EBI tubes are just too good to part with is one that I heartily agree with.  S/N is less important to me as it really should be converted to S/NdB and even a S/N of 40 is only S/NdB of 32.


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#5 Eddgie

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Posted 20 January 2020 - 06:22 PM

Eddgie has done a remarkable job of not just buying and evaluating a lot of different intensifiers but also taking the time to summarize his observations for others to digest.  I couldn't agree more with his conclusions regarding the weighing the importance of different parameters.  I have felt that if a person is going to pay the high price required for the very best tube out there then there needs to be some way to quantify that decision.  I also feel this quantification can be useful when buying used or at a better price point than the very top end.  Eddgie's conclusion that his very low EBI tubes are just too good to part with is one that I heartily agree with.  S/N is less important to me as it really should be converted to S/NdB and even a S/N of 40 is only S/NdB of 32.

Yeah, when I asked Ed Wilcox about the EBI before putting in a bid, he said it was unusual for buyers to care that much about it.  He said most people just want the highest SN they can get and he was kind of curious about why I was so concerned with EBI.

 

Hunters are a big part of the civilian market, and I have seen a lot of videos where hunters used IR torches so if you add any illumination, the EBI does not matter at all.   It is only when the device is used at the edge of the illumination threshold that this becomes an important parameter, but when running very narrow band filters, looking for the dimmest nebula in the field, then an IR Torch can't help you. 

 

Ed and I had a long email after the sale, and at that time, he asked a lot of questions about using NV for astronomy.  He of course has a Mod 3 with C mount, so when I explained how he could use a 1.25" nose or use narrow band filters, he was very interested.  He had heard of people using NV for astronomy, and he has a telescope, but he did not know how simple it was to do.

 

Anyway, Ed said most buyers ever ask about EBI and are only concerned about SN so my interest in this was something he was not accustomed to hearing or discussing, but we had a very nice conversation about it and last email we exchanged, he was shopping for a 6nm H-a filter! 



#6 GeezerGazer

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Posted 23 January 2020 - 03:10 PM

Most tubes I see people buying are reasonably balanced in that they are not the best in every spec, but no spec seems to be so low as to be concerned about getting satisfying performance.

 

I agree with this Ed.  It just makes sense to me.  My tube is not great in any specific spec, but is satisfactory for my needs... even having an EBI of 1.1   What it lacks in this spec, it makes up for in others.  

 

There are tradeoffs.  But I have never been concerned that I got short changed... although I have wondered what the difference would actually show, when compared to a very high spec, unicorn tube.  Your closet test results in the other thread seem to show how EBI (maybe mixed with other specifications) effects the image.  

 

During the 7 months in 2018-19, when I was hunting for a tube with substantially lower EBI, I found some with a lower EBI, but with other specs (PCR or S/N, Gain) that were substantially less than what I have.  So to accept these tubes might improve threshold H-a, but might put up an image of bright nebulae that is perhaps not as good as what I currently see with my average tube.  Those offerings were not an attractive option for me.  I chose to stick with my average tube and just enjoy what it shows me.  

 

This effort of searching for the unicorn, reminded me of my hunt for the perfect high power eyepiece for double stars as compared to the perfect high power eyepiece for planetary observing.  I purchased and sold many eyepieces in that endeavor and compared them in many scopes... deciding in the end, that each had strong points that were much more reliant on seeing and transparency to actually "see" a difference.  NV is different, with measurable specifications that we dwell on, to get the "best" possible image.  I mean, who wants to buy "average" if they can buy the "best"?   These specifications do or can make a difference under certain conditions and on specific subjects, but overall, I am quite happy with my average tube.  

 

I would love to compare the views between my Mod 3C and anyone else having one, but until I actually see the difference of a "better" image, I will not sell my tube to buy another.  But, since late 2016 when my Mod 3C arrived, I have NEVER had the opportunity to look through another NVD... not once.  None of the dozen seasoned observers I travel with once or twice a year to dark sites, have an NVD.  Moshen is the closest NV astronomer to me at 100 miles distant, and we have never met in person, although we have communicated often.  

 

As most here know, I am engaged in NV phonetography most of the time when under the stars, and I do prefer those images to the visual image through my Mod 3C.  Images are helpful to me and I really like that they provide a record of observations.  Even without a permanent image, I find that attaching my phone to the Mod 3C eyepiece and making the proper setting in Long Exposure mode of NightCap, provides an image on the phone screen that is nearly free from noise/scintillation.  I'm not talking about taking the image... just making the settings can provide an improvement over the image through the NV ocular in real time.  These days, my phone is usually attached to my NVD because of that improvement in the image.  If I set the exposure to 1second, the delay is annoying to me, but the image on the phone screen is much better defined, with better illumination for seeing increased detail... which is important for my aging eyes.  The adjustments within the phone and NightCap give me far greater control over the image than the NV gain control alone.  NV phonetography is an endeavor that I never suspected would be so satisfying, but it IS... and I really fell into it by accident, because my "average" Mod 3C made it possible.  

Ray



#7 chemisted

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Posted 23 January 2020 - 07:08 PM

Ray, I have a problem with you labeling your tube as "average".  To me all the specs are very fine.  Let me list them for you:  SNR=33.8, PR=2680, Gain=61433.  In my mind these combine to make a top tier tube (I like alliteration) and they have enabled you to produce the killer phonatography images that we have all enjoyed seeing.  If there is anything "average" about your tube it is true that, with diligence, others can obtain similarly performing equipment.  I think that is a good thing!  Ed


Edited by chemisted, 23 January 2020 - 07:09 PM.


#8 GeezerGazer

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Posted 23 January 2020 - 11:00 PM

Ray, I have a problem with you labeling your tube as "average".  To me all the specs are very fine.  Let me list them for you:  SNR=33.8, PR=2680, Gain=61433.  In my mind these combine to make a top tier tube (I like alliteration) and they have enabled you to produce the killer phonatography images that we have all enjoyed seeing.  If there is anything "average" about your tube it is true that, with diligence, others can obtain similarly performing equipment.  I think that is a good thing!  Ed

Ed, I do have a good tube.  But amongst the L3 filmless tubes listed in the tube spec thread from last year, I do consider mine pretty average.  I checked the other six L3 tube specs listed in that thread, 3 of which had two categories of specs that are higher than my tube; 2 listed 3 categories of specs higher than my tube; and one listed 4 specs higher than my tube.  I have no measure of other L3 tubes and I suspect that all of our tubes are higher, on average, than the average tube belonging to a paintballer, because we know to ask for and hunt for better specs to suit our needs.  Interestingly, I did seem to have the second highest (best) PCR, along with the highest (worst) EBI.  Five of the six had higher S/N than my tube, and four had higher Gain than my tube.  Of those who reported Halo in their L3, we all seemed to hover at .7 or .8.  So among these tubes, I do consider my tube pretty average.  

 

Yes, I agree Ed, that the opportunity exists with NV, for any astronomer to see more with their existing equipment, and even more with specialized optics that allow NV to perform at its best.  

Ray


Edited by GeezerGazer, 23 January 2020 - 11:12 PM.


#9 Eddgie

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Posted 24 January 2020 - 09:54 AM

Ray, I have a problem with you labeling your tube as "average".  To me all the specs are very fine.  Let me list them for you:  SNR=33.8, PR=2680, Gain=61433.  In my mind these combine to make a top tier tube (I like alliteration) and they have enabled you to produce the killer phonatography images that we have all enjoyed seeing.  If there is anything "average" about your tube it is true that, with diligence, others can obtain similarly performing equipment.  I think that is a good thing!  Ed

The difference between Ray's tube and the higher performance tubes is enough that one can see  but whether that difference would be worth it is highly subjective

 

I absolutely believe that nebula like the Horse Head will be brighter when viewed with a tube having a very high sensitivity and lots of gain and galaxies will also appear brighter in such a tube.  I have compared my average spec tube to Peter's and I believe I could pick them out in a blind test. 

 

I have used three tubes with very high PCR and gain. The first was the NV Depot F9800ULT with gain of almost 70,000 and PCR of over 2500.  The second was Peter's tube with gain of over 68,00 and PCR of over 2600.  The last was my newest tube, with gain of about 68,000 and PCR of about 2600.  I would say that all of these tubes have produced images of nebula that were a bit brighter than the lower gain and PCR tubes (2200 or or so, gain of 63,000, which is kind of what I see as average these days.)   In all of these high sensitivity, high gain tubes, things are slightly brighter.

 

Now the difference is subtle, but I think most people would see it.  Then it becomes subjective.. Is it worth moving from a f/7.5 ED scope to an f/7 Apo?  Is it worth moving from a 14" dob to a 16" dob? Is it worth waiting a long time to get it?  This is the kind of difference we are talking here.  Any of these will be a big jump over a PVS-7 (or should be or something is badly out of whack) or a "Bronze Spec" PVS-14, whatever that is but the step here is small.  I think it is enough to see though and for people with very large hobby budgets and patience, I recommend exercising the patience to get a tube that is at the top end of the performance spectrum as possible.   All of these tubes sell for about the same price, so the gating factor is patience.  

 

The tubes people are getting are all going to be a huge improvement over glass eyepieces and all will give fantastic views. Some will be a bit brighter than others though and when the devices from the different ends of the bell curve of "Premium" tubes are compared, I think most people would easily see the difference.  For most people that bought decently balanced tubes though, the difference is subtle. 

 

The subjective question is whether it is worth it to take the time to work with a vendor and the patience and perhaps higher price to get that small improvement in performace.  As with so many subjective questions, I choose not to speculate. 

 

I would take any late Gen 3 image intensifier I have ever owned, including my PVS-7s over a box of Naglers though..  When I look in the eyepiece of any of these, I see stuff that thrills me


Edited by Eddgie, 24 January 2020 - 10:08 AM.


#10 GOLGO13

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Posted 24 January 2020 - 10:58 AM

I have used three tubes with very high PCR and gain. The first was the NV Depot F9800ULT with gain of almost 70,000 and PCR of over 2500.  The second was Peter's tube with gain of over 68,00 and PCR of over 2600.  The last was my newest tube, with gain of about 68,000 and PCR of about 2600.  I would say that all of these tubes have produced images of nebula that were a bit brighter than the lower gain and PCR tubes (2200 or or so, gain of 63,000, which is kind of what I see as average these days.)   In all of these high sensitivity, high gain tubes, things are slightly brighter.

 

This comment is interesting. It could very well be that PCR and Gain are things to consider over EBI. While I've not looked through another device, the vibe I get from other folk's posts are those types of tubes may provide a brighter view and handle HA filters a bit better. My PCR and gain are on the lower end. That being said I still get a good view.

 

I would like to try getting better phone images. Maybe I'll order the TV phone adapter. I just don't really want to use an EQ mount...so I may need to get a tracking alt/az mount. But currently I own a EQ mount so that may have to do for now.



#11 Eddgie

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Posted 24 January 2020 - 12:56 PM

I do think PCR and Gain are important.  

 

A big part of the value propostion of filmless tubes is that they are supposed to be "better" than thin film tubes, but specs are specs and all tubes US tube have specs that are presented in the same way.

 

If you pay more for a filmless tube then, the logic would seem to say that you should expect specs that are higher than what you can get in a thin film tube, but often I see more expensive filmless tubes selling for more, and having some important specs that are not as good as the best thin film tubes. Now a big part of this is because people want the white phosphor and that does mean you probably have to go filmless, and likewise, people want gain control, and the best performing thin film tube model sold today does not have gain control.

 

I  have though said many times that I would not throw sensitivity and gain under the bus for a few decimal places of EBI because at the end of the day, the primary value proposition here is light amplification, and the more sensitivity you use, and the more gain you have, the more amplification you get, and the more amplification you get, the brighter a given subject will appear.  

 

Enough difference to wait months for a tube with very sensitivity and gain or pay a premium for it?  Totally subjective.

 

But yes, I think high sensitivity and gain do improve the view.   I doubt that anyone would struggle to tell the difference in brightness between a tube with 2000 sensitivity and 60,000 gain, and a tube with 2600 PCR and 69000 gain.   That is a pretty big difference.  Both do great astronomy, but better is better and a really high sensitivity tube with super high gain will produce a view that differs enough in brigntness that I think most people would see it easily.

 

I did this with Peters tube and my tube several times (his being about the higher specs here, and mine being the lower but a bit better than above).  We both agreed that his tube produced better views of galaxies.  I could see almost everything in both tubes, but again, we both agreed that his tube showed brighter galaxies and nebula.  Now this is a big gap and most people are getting tubes with better than 2000 sensitivity and 60,000 gain and the closer you get, the less the difference will be, but that is why I think knowing tube specs before you buy is important.  



#12 GOLGO13

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Posted 24 January 2020 - 01:09 PM

I'm thinking where this would probably come in handy are objects like the Horse Head Nebula. Seeing the snout detail could probably be easier with the brighter tube. My skies appear to be 19ish on the SQM scale. My best bet is with my 10 inch dob on a nicely transparent night. But still the snout is barely doable in the best conditions I've had. 

 

I can see the notch fairly well most of the time.

 

This is using 6nm astronomik or 8nm Chroma.

 

One thing I do find interesting is between the 12nm astronomik, 8nm chroma, and 6nm astromonik, The differences are not as extreme as it sounded like people describe. Maybe my eyes are not great right now. I can tell the detail is better with the 8 and 6. And I do believe there are times to use the 12. But I'm not seeing huge differences when I check between them. Only that some subtle details are better on nebulas. And for very faint objects, the 12 seems to do better.

 

I think my unit works very well for it's intended purpose and I don't think anything is wrong with it. I was able to use it recently in the woods and in a dark interior room and it was pretty awesome. 

 

And I do think it's good for astronomy as well. But I wouldn't mind trying out a tube with higher sensitivity and gain to see how that goes. I do know my unit seems to work the same in the cold as it did in hot weather. And that's probably where the low EBI helps.



#13 chemisted

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Posted 24 January 2020 - 01:16 PM

I don't think it is clear cut at all.  The interesting thing about Ray's tube is the very high Photocathode Sensitivity.  If you take 2200 as a benchmark it is 22% higher than that.  If you take 68000 as a benchmark for gain Ray's 61,433 is 90% of that so only 10% lower.  As Ray said, he has never had a chance to compare devices and that is why, as a group, we tend to rely on those of us with multiple devices to provide some evaluation and feedback.  Eddgie does an excellent job of this and is to be commended.  But even here it has to be recognized that these are analog devices that may differ from one another in subtle ways even when the numbers look quite comparable.  I developed my algorithms to determine if I would consider buying a tube with different specs and came to the conclusion that I would not either now or in the future.  I consider all of these top tier tubes to be very capable performers, but, as Eddgie just said, there can be small differences from one unit to another.



#14 GOLGO13

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Posted 24 January 2020 - 01:54 PM

I don't think it is clear cut at all.  The interesting thing about Ray's tube is the very high Photocathode Sensitivity.  If you take 2200 as a benchmark it is 22% higher than that.  If you take 68000 as a benchmark for gain Ray's 61,433 is 90% of that so only 10% lower.  As Ray said, he has never had a chance to compare devices and that is why, as a group, we tend to rely on those of us with multiple devices to provide some evaluation and feedback.  Eddgie does an excellent job of this and is to be commended.  But even here it has to be recognized that these are analog devices that may differ from one another in subtle ways even when the numbers look quite comparable.  I developed my algorithms to determine if I would consider buying a tube with different specs and came to the conclusion that I would not either now or in the future.  I consider all of these top tier tubes to be very capable performers, but, as Eddgie just said, there can be small differences from one unit to another.

Very true. I have nothing to compare to other than glass. And I can say with certainty that the difference is huge! Glass is still good though and I think there will be cases where I will prefer glass. 

 

Unfortunately some of my glass experience is only from memory. I've only been to truly darks skies a few times. I've been to moderately dark skies 20-30 times. Which is kind of sad when you think about observing over 17 years. But also points to why I felt it was important to try out NV. 

 

The other issue with my dark sky experience is I spent most of the time looking at the Milky Way. Kind of funny how that works out. 

 

Now I live fairly close to dark skies I should be able to get some better visits. Just need to look for a weekend that looks promising and get out there.

 

All things being said, I'm quite happy with my purchase. After selling the filter that came with it, It was $2900 total. While that's still quite a bit of money, it's pretty reasonable. It's actually my biggest single  astro-purchase by quite a bit. However, it has by a large amount rekindled the hobby for me. I tried to do some astrophotography but quickly realized it's not my thing. Maybe I'll dabble in that again someday. But for now NV is a much better fit. It's very much a  visual observing feel to me. 

 

I think for people looking to get into it, make sure you get specs and make sure they are above a minimum for each spec. What that minimum is I don't want to say myself but other posts talked to it. I think if I were spending $4K+ I'd want to ensure they were pretty good specs. But $4K to me maybe worth a bit more. Not to say I'm poor, just that would be a major purchase. And the more I think about $4-5K I'd be tempted to get a few pinball machines instead tongue2.gif 



#15 joelin

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Posted 24 January 2020 - 03:56 PM

I do think PCR and Gain are important.  

 

A big part of the value propostion of filmless tubes is that they are supposed to be "better" than thin film tubes, but specs are specs and all tubes US tube have specs that are presented in the same way.

 

If you pay more for a filmless tube then, the logic would seem to say that you should expect specs that are higher than what you can get in a thin film tube, but often I see more expensive filmless tubes selling for more, and having some important specs that are not as good as the best thin film tubes. Now a big part of this is because people want the white phosphor and that does mean you probably have to go filmless, and likewise, people want gain control, and the best performing thin film tube model sold today does not have gain control.

 

I  have though said many times that I would not throw sensitivity and gain under the bus for a few decimal places of EBI because at the end of the day, the primary value proposition here is light amplification, and the more sensitivity you use, and the more gain you have, the more amplification you get, and the more amplification you get, the brighter a given subject will appear.  

 

Enough difference to wait months for a tube with very sensitivity and gain or pay a premium for it?  Totally subjective.

 

But yes, I think high sensitivity and gain do improve the view.   I doubt that anyone would struggle to tell the difference in brightness between a tube with 2000 sensitivity and 60,000 gain, and a tube with 2600 PCR and 69000 gain.   That is a pretty big difference.  Both do great astronomy, but better is better and a really high sensitivity tube with super high gain will produce a view that differs enough in brigntness that I think most people would see it easily.

 

I did this with Peters tube and my tube several times (his being about the higher specs here, and mine being the lower but a bit better than above).  We both agreed that his tube produced better views of galaxies.  I could see almost everything in both tubes, but again, we both agreed that his tube showed brighter galaxies and nebula.  Now this is a big gap and most people are getting tubes with better than 2000 sensitivity and 60,000 gain and the closer you get, the less the difference will be, but that is why I think knowing tube specs before you buy is important.  

 

 

Is there a mathematical relationship between PCR and EBI?

 

For example, lets pretend you have two NV devices, A with EBI 0.1 and B with EBI 0.2.

 

Let's say A has a PCR 1000 can barely make out some faint signal. Would deivce B need a PCR of 2000 to resolve it (twice the response) given it it has an EBI of 0.2 (twice the background glow)....and keeping all other tube specifications constant between A and B?


Edited by joelin, 24 January 2020 - 03:59 PM.


#16 Eddgie

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Posted 24 January 2020 - 05:26 PM

Is there a mathematical relationship between PCR and EBI?

 

 

This is something I do not know for sure but this is how I think it works.

 

 

Tube gain is measured as the light output (in fL) divided by the light input (in fc). This is the measure that we see on the spec sheet. 

 

The spec sheet list "Luminance Gain" at both 2x106 and 2x104 in foot candles and I take that to mean that with a given luminance presented to the photocatode, you will have this much total amplification.  So, if I had a 6.9 lux per square millimeter of output and the tube had a .0001 lux input, that would be 69,000 gain. If I had a 6.1 lux per square millimeter output, and a .0001 lux input, that would be 61,000 gain.   Now this is "Tube Gain" and does not reflect the entire system gain, but it is safe to say that since all of the optics and housing are the same, then the tube gain would be the most reliable way to compare and spec sheets are for tubes and not the entire system. Now that difference above represents a 12% difference in brightness, and research says that a 12% change is greater than the brightness differential detection threshold, so yeah, when I use my lowest gain tube and I compare it to my highest gain tube (#1 vs #4 below) I can see that the highest gain tube is brighter. I should be able to see it, and I do see it.  It is just enough that I think the average person would see.  Now, if the gain difference were 65k Vs 68K, no, I don't think so.   

 

My thinking (and it is only my thinking because no one seems to have ever answered this question to me) is that the photocatode sensitivity is the input to the tube and the final figure accounts for the actual tube amplification.  That would mean that a weak photocatode feeding a tube with a bit stronger amplification at the microchannel plate might produce the same output brightness as a tube with a more sensitive photocathode and a slightly less powerful amplifier. 

We can assume that like any analog vacuum tube, individual tubes might vary over a small range of amplification, so I think the photocatode is probably a big player in that the more electrons you knock loose and send to the microchannel plate, the all things being equal, the more electrons you should get out.   If one amplifier is a little less efficient it would have a little lower total tube gain and if one were more efficient, it would have a little higher tube gain.

 

The big thing though is that the range of photocatadode sensitivity seems to be much larger than the amplifier variance because from most of the specs I see, typically, the more sensitive the PCR, the more tube gain.  That is not always true ****, but it seems to be fairly true in a general way.

 

No tube I have seen with a photocatode of less than 2500 has had a system gain of 69,000 but my newest tube has a photocatode of 2575 or something and only 68000 gain while my F9800ULT had 2505 PCR and almost 69000 gain.     

 

So, I do not think that it is linear, but I think the bigger variable is the photocatode and not the amplification factor.  I doubt that the actual gain of the tube itself varies more than a few percent but we see considerable variation in the system gain, and since in general terms, the higher PCR tubes also tend to have higher tube gain, it makes sense that the PCR is the major influence and the actual microchannel plate/tube circuitry secondary.

 

But I don't know if this is exactly right.  I have never been able to actually find detailed descriptions of how these correlated, but again, we have a lot of examples to work with, and in general terms, tube gain seems to be most influenced by PCR and for a given PCR, the strength of the amplifier might modify that positively or negatively a small amount depending on how many additional electrons the microchannel plate provides. Some might be a little better, some a little worse or the input voltage on the MCP might be a bit higher or lower.   Who knows, but probably the variance here is minor. 

 

If this is correct, then the PCR really sets the tone for the party electron party.  At least that is the way it seems.

 

The following are real tube specs with gain at  2x10 (Max is 80,000) and 2x10(Max is 21000)

 

PCR 2019..   62685 and 15500

 

PCR 2163     63945 and 15500

 

PCR 2505     68671 and  17777  ****

 

PCR 2572     68026 and 16925 

 

**** So, while it has a less sensitive Photocatohde the third tube (an F9800 ULT)  does have slightly more gain than higher PCR of the forth tube which is a filmless tube but in general, we can see that gain tends to follow PCR sensitivity. 

 

I can tell you that over the years, I have come to think that my early L3 tubes were not as good as my ULT except in EBI.  People are under the perception that filmless tubes are superior to thin film tubes, but if the specs are not as good, my experience is that the performace will not be as good. When you buy a tube you are buying performance and tube performance is given to us in the spec sheet. 

And once again I am compelled to say that even my lowest performance tube has been hugely rewarding to use and in the hot summer months, it has been great at detecting faint nebula, but for most things the higher PCR tubes have provided a bit brighter images, especially on nebula above the EBI threshold and galaxies.  Everything is just a bit brighter, and again, that is what amplification is supposed to do. It is supposed to make dim things brighter and the more amplification, the brighter those things should appear. 

 

And this last note.   The tube I wanted was the F9800 M24H.  Harris listed specs for it, but the US distributor can't get them.  I "Settled" for the new Filmless tube.  It was not my first choice but the F9800 M24H is simply not showing up in the civilian marketplace.  I prefer the characteristics of the thin film, P43 tubes, but we can't buy the best thin film tubes. This was supposed to be the promise of the filmless tubes, but in practice many are not as good as the best thin film tubes we an buy. 

 

Someone wise to NV hinted around at that, but at the time, I was too stupid to pick up on it. 

 

Sorry for the long post.. I have probably said way to much. 


Edited by Eddgie, 24 January 2020 - 05:32 PM.


#17 GeezerGazer

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Posted 25 January 2020 - 02:41 AM

Interesting to hear the correlation between PCR and Gain.  Thank you Ed.  



#18 Eddgie

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Posted 25 January 2020 - 08:52 AM

Interesting to hear the correlation between PCR and Gain.  Thank you Ed.  

Important to say that I have no expertise here.  I have four tubes with spec sheets that seem to show a correlation, but I am the first to admit that I don't have any of the tube electronic design theory.

 

In the best I can say is that the empirical evidence (we have a lot of tube data on CN) is that the PCR is the primary influence in tube gain, and that microchannel plate variations will modify that slightly, but sticking a highly sensitive PCR on a given tube will most likely raise the gain by the variance in sensitivity between its PCR and the PCR it replaces.

 

But I am not an expert.  I am just a guy looking at specs and drawing conclusion from them and that does not mean they are the right conclusions.  Only accept this if your own logic leaves you to the same conclusion.  My logic is not always reliable. 


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#19 Jeff Morgan

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Posted 25 January 2020 - 12:52 PM

Important to say that I have no expertise here.  I have four tubes with spec sheets that seem to show a correlation, but I am the first to admit that I don't have any of the tube electronic design theory.

 

Too bad the producers do not market directly to the consumer. In such a case, an inquiry might draw a reply from someone with such a background.



#20 Eddgie

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Posted 25 January 2020 - 01:50 PM

Too bad the producers do not market directly to the consumer. In such a case, an inquiry might draw a reply from someone with such a background.

Private citizens constitute a tiny tiny tiny fraction of tube sales.  The rely on the distributors and the dealers to promote the products because there is just not enough profit in this marketing channel to make it worth even having a part time employee playing around with marketing for this market segment.

 

The US government has purchased hundreds of thousands of devices over the years and law enforcement probably tens of thousands more. 

 

We have purchased 50 or 60.   Hunters are moving to thermal and we see this in used PVS-14 sales. 

 

So, private citizens are too small a market for them to care about.

 

Now even with telescopes, the manufacters often don't really provide much.  Most Apos sold today don't even show spot diagrams or publish polychromtic Strehl, so at least we have actual measured performance specs..


Edited by Eddgie, 25 January 2020 - 02:03 PM.


#21 joelin

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Posted 25 January 2020 - 11:57 PM

Is there a mathematical relationship between PCR and EBI?

 

For example, lets pretend you have two NV devices, A with EBI 0.1 and B with EBI 0.2.

 

Let's say A has a PCR 1000 can barely make out some faint signal. Would deivce B need a PCR of 2000 to resolve it (twice the response) given it it has an EBI of 0.2 (twice the background glow)....and keeping all other tube specifications constant between A and B?

I'm speculating EBI isn't linear..as in an EBI twice as high doesn't require double the PCR response to bring a faint signal just above the background glow...

 

because if that was the case, an EBI of 0.1 would be the ultimate device...I see as EBI goes from 0.1 to 1.0 in many of the sample device specs that have been shared on this forum...PCR tends to increase a bit...but maybe from 2000 to 2600....and not a 10x increase which would bring it to 20,000....

 

and Eddgie has said not to throw PCR under the bus for improvements in EBI...so it seems like the 30% increase in PCR from 2000 to 2600 should reasonably compensate for increases in EBI from 0.1 to values closer to 1....



#22 Alien Observatory

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Posted 26 January 2020 - 12:21 AM

Important to say that I have no expertise here.  I have four tubes with spec sheets that seem to show a correlation, but I am the first to admit that I don't have any of the tube electronic design theory.

 

In the best I can say is that the empirical evidence (we have a lot of tube data on CN) is that the PCR is the primary influence in tube gain, and that microchannel plate variations will modify that slightly, but sticking a highly sensitive PCR on a given tube will most likely raise the gain by the variance in sensitivity between its PCR and the PCR it replaces.

 

But I am not an expert.  I am just a guy looking at specs and drawing conclusion from them and that does not mean they are the right conclusions.  Only accept this if your own logic leaves you to the same conclusion.  My logic is not always reliable. 

I agree in totality, now if I could just understand the science behind this Post / Thread.. struggling to understand ... Pat Utah :)



#23 joelin

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Posted 26 January 2020 - 01:34 AM

with all the people on CN, I'm having a hard time believing no one can understand how it works well enough to clearly define how the specs relate to each other mathematically 

 

is it like some mystery that few know?


Edited by joelin, 26 January 2020 - 01:35 AM.


#24 Mazerski

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Posted 26 January 2020 - 10:58 AM

I’ll go out on a limb here and say most may not care about specs vs. math... I was out last night in hand-held mode with Nikon 180mm f/2.8 lens and once I point to sky and see stuff, I don’t even think about specs and equations. I just want to look.

 

My audio analogy is the same... you turn it on, sit and listen and slew rates, dynamic range, etc is not what your thinking about. 
 

The Rosette looked great last night - I’m not thinking about gain, EBI, or any of that stuff...I’m thinking how amazing it is that I can see it (and it’s rather large) with holding a device in my hand.

 

Seems to me with all the Qs you ask, your missing the point.

 

This: using both eyes with PVS7 @ EBI = 0.3 provides great view of nebulas

This: using one eye with Mod 3 @ EBI = 1.1 provides a better view of nebulas

 


Edited by Mazerski, 26 January 2020 - 11:11 AM.


#25 Eddgie

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Posted 26 January 2020 - 01:06 PM

 

This: using both eyes with PVS7 @ EBI = 0.3 provides great view of nebulas

This: using one eye with Mod 3 @ EBI = 1.1 provides a better view of nebulas

I have l said about half a dozen times now that EBI affects threshold performance. If you are viewing in an environment where the sky glow is providing more luminance than the EBI of the tube, then the sky glow is what sets limit of performance and not the EBI.

 

Did you know that M29 sits inside a nebula?  I didn't until I saw it myself.

 

I have seen all of the pink nebula in this picture using a .1 EBI tube.  There have many other tubes that would not show this nebulosity.  

 

Messier-29.jpg

EBI does not set the limit when observing from light polluted skies because the sky glow is stronger than the EBI level.  It is only when the sky level falls below the EBI level that EBI will have the most impact.  Again, I have see everything pink in the above picture but not with every tube I have ever owned.  My low EBI tubes though allow me to see it pretty easily, though sky conditions still have to be pretty good. 

 

You might want to try viewing the above scene with your two devices sometime.  The Nebula around M29 itself is a good example of an illumination source that is near the threashold of illumination and hence would be a good challange for EBI.

 

Remember, the Horse Head is (as these things go) pretty bright.   The Veil can be seen by an obsever using just a filter and no telescope, as can the North American Nebula.  Here, gain is what we see when we compare devices. To see the difference in EBI, you can't really use these very bright nebula because they produce a signal far above the EBI level. 

 

I mean it really is not that important to me for you to get the value of EBI.  If you are happy, that is all that matters, but some may be interested in what EBI looks like and what it does, and this post was really for those that care to understand the performance characteristics of image intensifiers.  If one does not really care, then this post would have been an enormous waste of time for them.




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