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.
Have an epic day, skywalkers!
Edited by Eddgie, 19 January 2020 - 11:44 PM.