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NVD Comparison and more...

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#1 GeezerGazer

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Posted 21 February 2020 - 12:34 AM

(Before you start reading this, extend the screen to the right; I prepared it separately in word processing and pasted here, so it does not wrap like when created here.)

 

I had the good fortune to be invited by Joelin to observe with he and Moshen in Mariposa, CA, on the 18th. He had rented an AirB&B for a few days at a nice dark location in the Sierra foothills, east of the central valley, only 90 minutes from where I live.  We started observing about 7 p.m.   In short order heavy dew had formed on all of our equipment… by 11, the dew had turned to ice.  We weren’t cold though… Moshen brought some great hand warmers! 

 

Joelin is an astrophotographer who is waiting for his ordered Mod 3C NVD to arrive.  Moshen and I brought our Mod 3Cs and I brought a second NVD that I just assembled last Saturday.  The “new” one is an AB Micro, using a 1x  C-mount Envis lens (from my Mod 3C), with a 12 yr. old F9800, thin film, green phosphor tube that had been originally part of a Collins I Cubed.  The specs on the tube are pretty average, well below most of what appears for astro use in this forum.  For comparison, here are the specs for my L3 white phosphor, the green Micro/F9800, and Moshen’s Mod 3C/L3 tubes:

 

            Ray’s Mod 3C/L3    Micro/F9800    Moshen’s Mod 3/L3

PCR     2680                       2274                 2574
EBI      1.1                           .9                      .5
Gain     61433                     57663               62647
S/N      33.8                        28.5                  33
Halo    .7                            1.1                     .7
RES    72 LP/MM               64 LP/MM        72 LP/MM
Mfg.    2016                       2008                  2017

 

Joelin used the Micro for some AP experiments during the evening, but later, we did some comparisons between the WP tube and the thin film green tube.  I have to say, I missed gain control on the Micro… but only for the first few minutes.  My eyes adapted to the bright image pretty quickly.  Skies were pretty dark; Joelin's SQM read 21.4

 

First, we sat down and passed around Moshen’s Mod 3C, and my Mod 3C for a comparison between them.  Try as we may, we could not detect a difference in the images presented by our two L3 tubes.  We wondered if threshold subjects might reveal some distinguishing difference between them, but we saw none at 1x.  You can see that our specs are pretty close on these L3 tubes.  The biggest difference between these two WP tubes is the EBI… but the temp was hovering near freezing, so it is likely that no visible difference in the EBI would have shown anyway. 

 

Then we held both Mod 3C devices at the same time, merging the image into a bino view.  Whoa!  That was amazing!  We both had an Astronomik 12nm H-a filter, so we put those on and tried the hand held BV mode again.  This was really eye-opening… literally.  Now I know what Eddgie and Gavster mean about the effect of NV binoculars being more than the sum of the parts!  Three differences make it pretty great:  first, the image is wider so I was seeing a larger FoV, second, there is a perceived overall brightness increase, and third, it’s just more relaxed viewing than with a monocular… perhaps the most important factor of the three.  

 

Then we compared Moshen’s Mod 3C and my Micro, holding the white phosphor or the green phosphor for quick, same-eye, comparisons.  I found that the Mod 3C with its WP tube, showed a very tiny bit more contrast when aiming at dark terrestrial spaces where trees provided a very dark background.  Just guessing, my thought was that the difference in gain and photo cathode response was presenting the slightly brighter image in the L3 tube.  However, turning both NVDs to the sky at 1x, where there was more light, there was almost no detectible difference in the image… equal brightness (Mod 3C using full gain), equal sharpness and about the same halo around bright stars. And, no bothersome scintillation in either device. 

 

We added the H-a 12nm filters, and here I saw a bit more difference in brightness, but it was quite subtle.  The Micro/F9800 presented a tiny bit more perceived scintillation, so the tube was probably working a bit harder with less available light because of filtration.  Pointing the Micro at the stars (where more light was available), I could see no difference in contrast between the Mod 3C and the Micro, except for the color difference.   Stars were just as bright and sharp in the Micro as the Mod 3C, and there was only a slight bit of scintillation; it was far from being distracting.

 

THEN, I held both the Micro and Mod 3C up (both at 1x with gain turned all the way up on the Mod 3C) and merged the image like a pair of binoculars again.  WOW!  The really strange aspect of this “experiment” was the way my eyes/brain merged the color of the two NVDs.  With one green and one white phosphor tube, the merged image appeared as a slightly greenish-blue tint for both of my eyes.  This seems like a game changer to me.  If a lower spec tube (read that as less expensive tube) can show the night sky this well when used with a higher spec tube, then NV BVing is within the realm of possibility for a larger number users. 

 

Cost?  I purchased a brand new Micro housing kit from NVD with ocular for $525.  The 12 yr. old F9800 thin film tube was $900.  Now, I have ordered two Computar V5013 C-mount objective lenses $100 each to use with my Micro and Mod 3C, along with two $5 step rings so I can use my 2” filters as first surface objective filtration… for 2x BV observing.  I’ll report back on this continuing “experiment” in a few weeks.

 

Thanks to Joelin for getting us together.  Thanks to both Joelin and Moshen for such a great evening… and to Moshen for sharing his NVD for the comparisons.  We had lots of NV discussions during the evening.  The next morning, we had a late breakfast and chatted for 2 hrs. before heading home.  Although Moshen and I have known each other on-line for 2.5 years, this was our first in-person greeting, and it was a great pleasure.


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#2 outofsight

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Posted 21 February 2020 - 01:14 AM

Thanks for the absolutely excellent report. Sounds like a good time! 


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#3 GOLGO13

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Posted 21 February 2020 - 07:19 AM

Very cool, but now I am worried for my wallet! Hah. Maybe sometime in the distant future. What was Joelin's impressions? Sounds like a great night.
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#4 chemisted

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Posted 21 February 2020 - 08:52 AM

Thanks for the great report, Ray.  Since I have an original Collins I3 I have done some comparisons with  my NVD Micro that I think might add some fuel to your fire.  This very old unit (ancient?) preceded thin film tubes and has PCR <2000, gain <60,000 and SNRdB <27 but a very low EBI by my estimation.  Last fall I did a comparison using my 140mm refractor with a reducer that got me to f/4 in combination with an Astronomik 12nm filter.  My first target was the Pacman nebula.  Both devices gave an excellent view with the Collins unit being a little dimmer but with equal, if not better, contrast.  It had more of a greyish cast and, to tell the truth, I actually liked it a bit better than the Micro view so I continued on to all those great sights in Cygnus.  They were all just as gorgeous and enthralling with the older Collins unit compared with my newer device even though perceived brightness was less.  These are some of the reasons I have encouraged people in the past to pick up a used unit at a good price if one can be found since Generation 3 tubes have always been very capable if properly chosen.  I continue to think that Bill Collins went through very many tubes from those available at the time to find ones that would perform well with a telescope.  


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#5 GOLGO13

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Posted 21 February 2020 - 09:05 AM

I think Mr. Collins also had a lot of experience since I saw some advertisements for his night vision units in some of my older Sky and Telescope magazines.

 

This one from 2002:

 

collins1

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#6 chemisted

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Posted 21 February 2020 - 09:39 AM

He most definitely had a lot of experience as his home telescope was the incredible 7" Apo refractor from Astro-Physics.  Thanks for the old ad!  I bought mine in March of that year.


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#7 Jeff Morgan

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Posted 21 February 2020 - 12:28 PM

Nice write-up Ray! Quite interesting, but I think my second NVD is a year out - at least.

 

We amateur astronomers tend to be an OCD bunch, and I see a lot of specification anxiety among the newer buyers.

 

As I read your report, it appears to support what I have advised prospective buyers on the forum - just get in the game! These tubes are like snowflakes (no two exactly alike).

 

Any of the new tubes should deliver game-changing results - but only if you are in the game.


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#8 GeezerGazer

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Posted 21 February 2020 - 01:55 PM

I'm sure Moshen and Joe will add their thoughts and opinions soon. 

 

I did purchase a brand new thin film, I cubed from Bill Collins about 2010 or 2012, but it was the wrong time of year here in the central valley, with high levels of dust and smoke in the air which severely degraded the effectiveness of NV.  When I called Bill about my problems, he asked me to return the unit for a refund, saying that the Central Valley of CA was known as one of the worst areas in the US for NV astronomy.  I gave up on NV until 2016, when I purchased my Mod 3C.  Even now, I rarely observe from home because of conditions here.  Driving 40 miles at 900' higher elevation gets me to darker skies and out of most of the muck in the air here, where both glass eyepieces and my NVD are able to perform much better.  That 40 mile drive is better than ANY filter I've ever used from home.  

 

Jeff, I agree with you.  The big step is choosing NV... the specs seem to be of less concern.  Specifications do matter, but the degree to which they matter, seem to be less important than I previously thought.  Certainly, the differences I saw between these tubes was far less than I anticipated.  But like most other aspects of astronomy equipment, small differences can be much more important to some than others... each of us has different preferences and tolerance levels.  Someone else might see differences between these tubes that I don't see, but for me, under the conditions of the night, the differences were very subtle.  Just like with glass eyepieces, performance improves with perfect seeing and transparency.  The conditions on Tuesday night were far from perfect with lots of humidity... dew was very heavy.  Given that our comparisons were carried out under those conditions, results could possibly change with better conditions.  The results were for one night, at one location, with three sets of eyes.  What was most surprising to me, was how well the older, thin film tube compared to the much newer filmless tubes.  Eddgie has spoken of these subtle differences in the past, preferring the thin film tube to filmless for tighter star images.  I personally did not see that distinction in this comparison, but what I did see was that the differences between these tubes is really quite subtle.  

 

Thanks for the great report, Ray.  Since I have an original Collins I3 I have done some comparisons with  my NVD Micro that I think might add some fuel to your fire.  This very old unit (ancient?) preceded thin film tubes and has PCR <2000, gain <60,000 and SNRdB <27 but a very low EBI by my estimation.  Last fall I did a comparison using my 140mm refractor with a reducer that got me to f/4 in combination with an Astronomik 12nm filter.  My first target was the Pacman nebula.  Both devices gave an excellent view with the Collins unit being a little dimmer but with equal, if not better, contrast.  It had more of a greyish cast and, to tell the truth, I actually liked it a bit better than the Micro view so I continued on to all those great sights in Cygnus.  They were all just as gorgeous and enthralling with the older Collins unit compared with my newer device even though perceived brightness was less.  These are some of the reasons I have encouraged people in the past to pick up a used unit at a good price if one can be found since Generation 3 tubes have always been very capable if properly chosen.  I continue to think that Bill Collins went through very many tubes from those available at the time to find ones that would perform well with a telescope.  

Ed, interesting commentary, which does resonate well with my findings.  

 

This was a fun comparison to do.  It was completely subjective, so keep that in mind.  

 

I am very happy to have put this Micro together, especially for it's relatively modest cost.  Even with the 50mm objective I ordered yesterday, total cost is $1530... a far cry from $4,000.  I pause to reflect on the $2470 difference between it and my Mod 3C... differences which I see and describe as subtle.  

 

So the question becomes, at what point do specifications make a distinct difference?  And, are those differences worth the cost for your style of viewing?  If using a 3nm H-a filter (which I don't have) is your goal, then perhaps a higher gain or photo cathode response is of necessity.  If viewing from very warm climes, then a lower EBI might be of significantly greater value for summertime performance.  But if you want it all, with the highest/lowest specs in every category, then not only will you have to wait, but you will also have to pay.  Tubes vary, as Jeff says, like snowflakes.  If the perfect snowflake is your goal, then you have to wait for it in the cold.  This comparison revealed to me how some pretty significant spec differences are manifested as quite subtle NV improvements.  

 

I would really like to hear input about my observations from CN members Cnoct, Jdbastro and Eddgie who all have experience with multiple types of NVDs using different types of tubes.  Their input would be much more valuable than my limited experience, now with just 3 NVDs.  


Edited by GeezerGazer, 21 February 2020 - 02:03 PM.

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#9 chemisted

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Posted 21 February 2020 - 03:12 PM

I can make a few additional comments on specifications as they relate to intended usage.  As you know, my Collins I cubed performs very well on distant globular clusters when used with my 10" reflector.  Trying to do the same with the 5.5" refractor is just not possible because it doesn't have the amplifying power when fewer photons are presented at relatively high f/ratios.  As I describe above, faster f/ratio targets are just fine.  I believe this has more to do with photocathode response and gain than it does with SNR.  Additionally I have convinced myself that the very low EBI of my Collins unit gives me a contrast benefit that enables me to see the very faint stars of clusters that would be swamped by a brighter background.

 

The Micro I have is an excellent modern device and I have one more anecdote to share in comparing it to the I3.  Also last fall I used the 10" at prime focus to observe NGC 6760 first at f/9.3 (25' FOV) and then at f/15 (17' FOV).  Both devices gave me beautiful views of dozens of stars at the faster f/ratio however when I changed to f/15 an interesting thing happened.  The Collins device apparently became photon starved and I lost a substantial number of stars.  The Micro, on the other hand, if anything gave a better view with more detail as I had hoped.  Changing back to f/9.3 once again gave views that were very nice and detailed with either device.

 

This all supports the contention that you can do an enormous amount of phenomenal viewing with any of these gen 3 tubes but only, as Jeff says, if you are in the game.  To quote a comment I made some years ago one should get one of these as soon as possible to start enjoying the good life.


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#10 outofsight

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Posted 21 February 2020 - 04:28 PM

"Jeff, I agree with you.  The big step is choosing NV... the specs seem to be of less concern.  Specifications do matter, but the degree to which they matter, seem to be less important than I previously thought." From #8.

 

This may have been what kennyrichmond was trying to convey in joelin's, "The frustrations of getting into NV" thread. Specifications, compared to simply buying any decent Gen 3 device, are probably overrated. In other words, if you don't already have an NVD, then your best move is to get one, and it will provide a massive boost in your viewing capabilities. You don't need the latest, greatest tube, because, in a way, there's no such thing. As Jeff Morgan said, "tubes are like snowflakes," no two are exactly alike. And unless you have two to directly compare, you'll hardly know the difference. 

 

So, first you do your research, and then you get any setup from <$1K to $4K or so, and you'll have an extreme boost in what you can view. And as in all of astro-equipment, the $4K system will not show you 4 times as much as the $1K system, the 4K boost will only be marginal (maybe 10%, very hard to say). So if you just want to try NV, you don't have to spend so much and you shouldn't get hung up on specs. But to spend on the low end you should do more research and have a good understanding of NV devices. But if you're spending a lot more, then do enough research until you are very comfortable and sure of your purchase.

 

Also from post 8. "I would really like to hear input about my observations from CN members Cnoct, Jdbastro and Eddgie who all have experience with multiple types of NVDs using different types of tubes.  Their input would be much more valuable than my limited experience, now with just 3 NVDs."

 

I will slightly disagree, not that their input wouldn't valuable, but whatever their input would be, it cannot take away or add to what you have seen in your own little experiment. Seeing is believing, you saw what you saw, directly comparing the devices. Unless it was an illusion, or you are deluded, you know that what might seem to be a lesser device can be quite good for viewing, and would be of great value to someone who wants to try night vision but isn't sure how to start. 

 

Let's face it, for many of us, spending $1K is at least 4 times easier than spending $4K, and spending $4K won't get you 4 times the quality of view. For anyone who's thinking about NV, don't overly concern yourself with the specs, concern yourself with adequate research and reasonably expectations and knowing what you're buying. Have fun with it.


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#11 moshen

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Posted 21 February 2020 - 05:16 PM

Thanks Ray for the well written observing report! I had a great time.

 

Joe was imaging with his C8 HD SCT and a smaller refractor. Ray brought his TEC140 and Explore Scientific 8" F4 newt. I chose to bring my dew-magnet C9.25" SCT. Skies were dark however humidity was high and thus transparency was average at best.

 

As Ray noted we couldn't distinguish a difference between our L3 unfilmed Mod3 tubes. We tried unfiltered and filtered with 12nm Ha. The major difference between our tubes is EBI and temps that night hovered around 32f so comparisons in much warmer weather may reveal a different outcome.

 

Ray's Micro/F9800 he put together for $1.4k was very good. Comparisons between it and the newer L3 unfilmed tubes mostly began showing their differences when looking at the pitch dark trees. There is more scintillation/noise noted in the older thin-filmed tube. Against the sky, there's enough background light both units showed remarkably similar views. There is still a bit more noise in the older green thin-filmed tube but it was easy to forget and mostly noticed when comparing to the L3 unfilmed. It may be preferable to many to build two of these thin-filmed green tubes for bino-viewing at a lower combined cost than one high-spec unfilmed white-phosphor monocular.

 

I also got to try Joe's 50mm Gary Russell Plossl EP afocally with my NV device. This brought my F10 SCT to a faster effective focal length when NV viewing. I think the 50mm Gary Russell coupled to the NV with the Rafcamera T2 to Envis adapter is a great alternative (lighter in weight & less cost) than the TeleVue 55mm Plossl and TeleVue adapter. The 50mm Gary Russell is very light with a body of machined delrin. It won't be as well corrected at the edge as a 41mm Panoptic but it trades off with much less weight, size, more focal reduction and less cost.

 

When Joe gets his Mod3 NVD in I'll try to get together with him and do another comparison. His incoming tube has slightly higher SNR & gain than mine.

Huge thanks to Joe for the invite to observe with him in the Sierras & it was a real pleasure to finally meet & observe with Ray.


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#12 joelin

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Posted 22 February 2020 - 02:04 AM

I had an excellent and enjoyable end of my 4 day stay in Mariposa with Moshen and Ray. Many thanks to both for bringing some NV gear to share as I'm still waiting on my NVD to arrive. I had acquired a number of accessories to expecting my NVD to arrive but it was delayed. Instead I focused on perfecting my astrophotography setup and doing some visual. I had my AT60ED on my Sirius mount connected via EQMOD. I captured data with the ASI1600 mono and LRGB filters. It was a challenging setup as many issues were uncovered over the few days and some aren't fully resolved yet. Astronomy software is quite hard to use!! I also had an Edge 8" on a Tak EM-200 doing visual by plate solving using an attached camera lens on the top dovetail. I followed Sue French's Deep Sky Wonders. For anyone who is bored with the sky because you've already seen M42, M31....read the book and Sue French writes in a way that brings magic to familiar objects as well as pointing out less familiar but just as wondrous objects.

 

Of the 4 nights, the first night was mostly clear, maybe 1/2 hour observing time lost in the early evening due to significant haze. The second night was mostly clear, the third night partly cloudy due to haze, but mostly clear after midnight. The final night was clear. 

 

Moshen and Ray arrived the final night. I did get a chance to use Ray's Micro. I attached my Sony A7S to the back side of it using a 28-70mm lens with the PVS-14 camera adapter. The adapter is quite hard to use but Ray showed me how to get it on. The ring must go down the ocular of the NVD first, and then slide up once you have the two halves of the circle firmly gripped and pressed against the ocular. With it I was able to mostly fill my frame at 50mm and have a reasonably secure connection to the NVD. One thing I did not like was how easy it was to rotate the setup due to the diagonal. I may look into doing a straight threaded connection if the weight isn't too great. 

 

With the camera on the NVD, I put LRGB filters in the diagonal and will attempt to do a color image of M42. I don't know how well that will turn out but I will say that dew may have impacted the images. It was very dewy with the top of my table feeling moist as early as 6PM. Most of that moist was frosty by 11PM. I'll work on these images and hopefully share something soon. 

 

Around midnight I took a short nap and got up to see Ray and Moshen testing their NVD. I got to put the Micro green phosphor in one eye and the Mod 3 white in the other. Surprisingly I could merge the images. The image quality was just about the same when pointed at the sky, but I could tell there was somewhat more contrast in the dark areas where trees were. The Micro offers incredible value at the prices Ray paid for! I tried to look for the faintest stars in a small triangle area in the sky and counted roughly the same number of stars between the Micro and Mod 3. I wrapped things up by 130am. 

 

Many thanks to Ray and Moshen for sharing their NVDs and writing up the observing report. I was really impressed to see how quickly Ray accumulated a bunch of images from using his phone and NVD. Its satisfying to walk away from a single night like a dozen usable photos. Now if it is possible to turn them into color....I am investigating right now. 


Edited by joelin, 22 February 2020 - 02:05 AM.

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#13 Jeff Morgan

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Posted 22 February 2020 - 11:57 AM

I also got to try Joe's 50mm Gary Russell Plossl EP afocally with my NV device. This brought my F10 SCT to a faster effective focal length when NV viewing. I think the 50mm Gary Russell coupled to the NV with the Rafcamera T2 to Envis adapter is a great alternative (lighter in weight & less cost) than the TeleVue 55mm Plossl and TeleVue adapter. The 50mm Gary Russell is very light with a body of machined delrin. It won't be as well corrected at the edge as a 41mm Panoptic but it trades off with much less weight, size, more focal reduction and less cost.

 

I got a first look at the Russell SP50 a few weeks back, using it on a f/6 SV80 refractor.

 

In a short session it did very well vs. the Tele Vue 55 Plossl. Somewhat smaller true field, but somewhat larger sharp field.

 

On paper there should be a brightness advantage to the 55 but I have not evaluated that yet.

 

A few more sessions with different scopes are in order for a full vetting, but early results are encouraging. And the T2 connection is a huge improvement to the DioptRX clamp ring.


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#14 PEterW

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Posted 22 February 2020 - 12:20 PM

Be interesting to see how the older tubes fare as the filter bandwidth gets smaller. The new tubes work very nicely with 3nm, though most of us never make it below 6 or 7nm.

Rule number 3 of NV Astro (number 1being to use fast optics, number 2 being get a low EBI)... is NEVER try using 2 units as binoculars... it’s fatal for your wallet!!
I had the misfortune of seeing the effect with Gavstar, using 2 different technology modern tubes (which do show subtle differences), when using both barnards loop and the angelfish nebulae just popped into view, where otherwise they weren’t there. Great report!

Peter
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#15 GOLGO13

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Posted 22 February 2020 - 03:28 PM

... is NEVER try using 2 units as binoculars... it’s fatal for your wallet!!
I had the misfortune of seeing the effect with Gavstar, using 2 different technology modern tubes (which do show subtle differences), when using both barnards loop and the angelfish nebulae just popped into view, where otherwise they weren’t there. Great report!

Peter

This is terrible news Peter!!! bawling.gif gaah.gif

 

I'm above my budget on NV as it is...haha.



#16 GeezerGazer

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Posted 22 February 2020 - 07:29 PM

I got a first look at the Russell SP50 a few weeks back, using it on a f/6 SV80 refractor.

 

In a short session it did very well vs. the Tele Vue 55 Plossl. Somewhat smaller true field, but somewhat larger sharp field.

 

....the T2 connection is a huge improvement to the DioptRX clamp ring.

Jeff, in 2018 when I purchased the TV PhoneMate and lens adapter I thought it worked OK.  But I also preferred the screw connection between the Russell Super Plossl eyepieces (50 & 65mm) and the NVD.  It's just a nice solid, simple connection.  I wish I had sent you the 65mm to test before I sent it to Ed.  I like to see testing in different optics... gives a better perspective of performance, from more eyes, under different skies (LP), and with a variety of scopes.  

 

The difference in focal reduction when using NV with the three lenses is quite substantial.  The advantage of of the 65mm is that it may not require an additional dedicated reducer in the mix to get to a really satisfactory focal ratio.  

     Russell SP 50     .52x reduction

     TV 55 P               .47x

     Russell SP 65     .4x

So where the 50mm takes your f6 scope to f:3.1, the 55mm to f2.8, the 65mm brings it to f2.4... I believe that you could detect this difference using it visually.  

 

Are you using any additional spacers between the eyepiece and the NVD objective, other than the M48 to M42 step down ring and the M42 to Envis adapter? 



#17 Jeff Morgan

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Posted 23 February 2020 - 12:51 AM

Are you using any additional spacers between the eyepiece and the NVD objective, other than the M48 to M42 step down ring and the M42 to Envis adapter? 

 

I did not use the 48->42 ring at all. Used only the 42->ENVIS ring from RAF Camera. Adding some T2 spacers is on the To-Do list.

 

Sadly work, weather, and social calendars have been totally out of phase.


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#18 GeezerGazer

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Posted 25 February 2020 - 01:20 AM

It didn't take long for my C-mount, 2x Computar objective lenses to arrive.  This particular lens, recommended by jdbastro and Moshen, is a very nice, compact CCTV lens that remains sharp almost to the edge of field, is easy to focus and has an adjustable, manual aperture.  I read a post several months ago how when using the Micro which does not have adjustable gain, that using an objective aperture seems to perform similar to a gain control.  I tried that and as long as the aperture is not stopped down too much, it does darken a very bright image.  I think I will enjoy these two objective lenses... thanks Moshen.  

 

Next, I tried out my Mod 3C and Micro in bino mode.  Last Saturday I worked on a simple device to mount up the two NVDs as a binocular.  It works well for me, and although the IPD is set by the spacer between the two units, I made 3 of them in different widths to accommodate an IPD span of 5mm .

 

The connector between the two units is simply a 1/4" x 20 tpi screw without a head, cut to the proper length.  I made a few spacers from ABS, HDPE and aluminum... in the future, I'd stick with HDPE.  It's a little softer than the ABS and doesn't leave marks on the black NVD housing like aluminum.  And, it's really easy to drill and tap.  The aluminum connector looks like this (each spacer looks the same except thinner or thicker): 

 

IMG_7181.jpg

 

I screw the connector into one NVD, then screw on the other NVD.  The connector keeps the NVDs perfectly parallel so I only need to adjust one axis to merge the image.  I tried it tonight and was super please.  I also found that mixing first surface filters, matters not a whit.  I had a 12nm H-a on the Micro and a 7nm H-a on the Mod 3C... brain power merged and collated the image just fine.  Testing from my red zone home with a LED street light 20° from Barnard's Loop, an interesting phenomenon... when I closed one eye and looked through the Mod 3C with 7nm H-a filter, I could JUST BARELY see Barnard's Loop.  With the Micro/12nm filter, I could not see it at all.  But with both eyes open, and both NVDs on, I could see just about the entire Barnard's loop in BV mode.  That was a surprise to me.   

 

Is the connector a perfect solution?  If you want to share the BV experience, it's a little cumbersome because you'd need a whole range of spacer widths and to change the IPD.  But for me, it's all I need.  It's simple to make, light weight and small and does a perfect job of aligning the two NVDs.  When the two units are attached to one another, the oculars are not perfectly parallel with each other, one is 2mm longer than the other... which means the mounting point is in a slightly different position in the housings.  This did not seem to make a difference to me for visual use.  

 

I did enjoy using my NV Binocular tonight.  I know it will be so much better when I take it to my darker observing site and sit in my lounge chair!  

 

So what does it look like?  

 

IMG_7175.jpg

 

IMG_7176.jpg

 

IMG_7178.jpg

 

 


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#19 GeezerGazer

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Posted 25 February 2020 - 01:30 AM

I forgot to mention one more thing... I think it was Chemisted who posted that he finds perfect focus with certain objectives and afocal lenses by moving the diopter adjustment on the NVD.  I tried this with the Micro and found that it did perform much better at -1.  This was true also with the Envis lens and with my camera lenses.  Whereas, with the Mod 3C, it performs best with all lenses at -0- diopter adjustment.  I believe the ocular on the Micro and the Mod 3C are exactly the same, but something else is different to require this adjustment.  



#20 joelin

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Posted 25 February 2020 - 04:25 PM

Interesting...so you set the lens to infinity focus and then the diopter to -1 or the other way around?

Also, what adapter do you need do the filters can thread on?
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#21 moshen

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Posted 25 February 2020 - 05:02 PM

Nice and clever way to mount both monoculars!


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#22 Eddgie

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Posted 26 February 2020 - 12:06 AM

The eyepiece diopter ring on the PVS-14, Micro, and Mod 3 has something of an "arbitrary"  -0- position.

 

What I mean by this is that the actual spacing of the focus of the -0- position can be varied by the user.

 

Between the dipoter adjustment and the housing, there is a wide flat black ring with small holes around the outside. This is the stop ring for the eyepiece travel adjustment.

 

If one finds that -0- is not perfect focus, one can make it so by srewing the lock ring toward the housing several turns.  Next, the diopter would be set so the -0- alignes to the dot on the base of the eyepiece.  Now, with the locking ring out of the way, the entire eyepiece assembly can be scewed further down on the treading to move it closer to fiber output window,  or out away from the window as necessary, to get the eyepiece into sharp focus.  Once sharp focus is achieved. the lock ring can be screwed back up to the base of the eyepiece assembly to lock it in place.

 

Now one would assume that this adjustment would be made with the user using their glasses or other corrective optics to ensure that they have proper infinity focus when doing this proceedure.

 

So, it is kind of an arbitrary setting that the user may tweak to their own preference.  

 

 

Mine is set to -0- for both eyes when wearing my glasses, and when I am not wearing my glasses, I have to adjsut my right diopter to by 1.5, but my left eye can stay the same. 

 

And a note. Once the lock ring has been backed away, it can then be turned up so that it gently touches the eyepiece assembly.  At this point, the eyepiece assembly can be completely unscrewed and this exposes the fiber optic window for cleaning (if necessary). This should not be done to a PVS-14 that has been purged in that is should not be necssary to every clean the fiber output window. There are ways the user can purge the PVS-14 on their own, but I would check to see if removal of the eyepiece voids the warranty.  Since the Micro and Mod 3 are often used at prime focus, purging is not that big a deal, but the objective or eyepiece is ever removed in high humidity conditions, I recommend opening it in dry environment when possible.  It has to be pretty high humidity to have issues with internal fogging, but it can happen. Purging C mount devices that are often used at prime focus is of course not really very pratical.  I never purge mine even though the ENVIS lens makes the housing air tight and waterproof.  My evironment is generally not very high in humidity and I have not had issues with internal fogging, but it can happen.

 

And one more note.  On the infinty lock rings on the PVS-14, PVS-7 and ENVIS lens, there is a tiny tiny hex lock screw.  There are similar holes in the eyepiece diopter position locking ring.  None of mine have ever had set screws in them, but I do not know if it is common practice to use them in the PVS-14 eyepiece lock ring.  If the ring cannot be moved by hand, I would check for the presence of such a hex screw.  Unless you are me, it is unlikey that you will have this wrench.. It is tiny tiny tiny.  I have one, but do not remember the size and am out traveling around these days, so I can't dig out my set of hex wrenches, but I promise you that this wrench is unlikely to be in the vast majority of standard hex wrench sets.   Again, I regret that I do not remember ths size.

 

So, you can set the -0- position anywhere you like.  -0- To the indicator, losen the lock ring, and screw the whole eyepiece in or out as necessary to bring the fiber window into best focus, then tighten the ring against the base of the eyepiece assembly.


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#23 GeezerGazer

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Posted 26 February 2020 - 02:15 AM

Interesting...so you set the lens to infinity focus and then the diopter to -1 or the other way around?

Also, what adapter do you need do the filters can thread on?

Joe I focused the objective on stars and then moved the diopter until stars were their smallest and sharpest.  Refocusing the objective did not improve the image.  The Computar V5013  50mm lens has 46mm filter threads, so I used a 46mm to 48mm step up adapter ring.  



#24 GeezerGazer

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Posted 26 February 2020 - 02:21 AM

Thanks Eddgie, great information, especially about moisture and purging. 



#25 chemisted

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Posted 28 February 2020 - 08:04 PM

Ray, You are being a most impressive influence on me.  First the Russell 65mm and now NV binocular.  Today I ventured forth to an old-timey camera shop in my new locale and asked about C-mount objectives.  The owner, who was walking out to get lunch, immediately detoured to a long forgotten shelf and produced a Fujinon 50mm f/1.4 CCTV lens that is absolutely new and sold it to me for a song.  He confided he had lots of stuff that he periodically asks himself WHY DO I KEEP THIS only to find out that there is someone like me who shows up at the door with a use he never imagined.

 

I plan on putting this on my I3 with the 12nm filter and using the Micro with my 50mm Nikkor and 7nm filter to approximate what you have done.  I'll post how it turns out.  Thanks again for the incentive to try this!


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