Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

MOD3 WP Honeycomb

  • Please log in to reply
87 replies to this topic

#51 jay.i

jay.i

    Mercury-Atlas

  • *****
  • topic starter
  • Posts: 2,893
  • Joined: 11 Jun 2017
  • Loc: Minneapolis, MN

Posted 30 August 2020 - 02:45 PM

No it is not. My Gen 3 WP tube does not display this pattern, at least not to this extent.

And it's from L3? Can you provide some pictures?


  • Tyson M likes this

#52 jdbastro

jdbastro

    Viking 1

  • *****
  • Posts: 825
  • Joined: 18 Aug 2007
  • Loc: Commie Calif.

Posted 31 August 2020 - 12:27 AM

jay.i,

 

Your tube rocks!   I have owned over a dozen recent vintage image tubes (Gen 3 thin-film and unfilmed, white phos and green).  Given similar performance specs, Unfilmed generally outperforms thin-film every time.  The FPN on unfilmed tubes from L3 is a feature, NOT a flaw.

 

Enjoy your tube.

 

Oh, and I'm not a vendor.



#53 cnoct

cnoct

    Apollo

  • *****
  • Posts: 1,086
  • Joined: 02 Sep 2010
  • Loc: Hawai'i

Posted 31 August 2020 - 03:47 AM

Just reference MIL-PRF-A3279602, won't change opinions but WTHay...
 
"Fixed pattern noise.
 
Multi-to-multi pattern variation.
With the operating potential applied to the assembly and the entire -4
photocathode uniformly illuminated at a level of 1 to 2 x 10 fc, multi-to-multi brightness deviations from the mean value shall not exceed ± 10 percent.
 
Multi-boundary pattern noise.
With the operating potential applied to the assembly and the entire photocathode uniformly illuminated at a level of 1 to 2 x 10 fc, the average value of the brightness deviations of the multi-boundary intensities shall not deviate from the mean value of the adjacent multi intensities by more than ± 10 percent. The mean value shall be established from the three adjacent multies containing the above multi-boundaries."
 
Google MIL-PRF-A3279602.pdf to bring up the PDF on GovTribe.com or other site.

Hmm J, not a vendor eh, spidey sense tingling...

#54 Astrojedi

Astrojedi

    Fly Me to the Moon

  • *****
  • Posts: 5,770
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 31 August 2020 - 06:21 AM

My point was a bit different. I work in semiconductors and Ga amplifiers are used in many applications including RF as well. Such large variations in performance would be unacceptable in all applications that I am aware of. But somehow in this industry vendors treat it as normal.

Maybe there is a good reason for it but in my experience fat govt. contracts are almost always a disincentive for innovation and investments in cost reduction. Given the level of control exerted by the govt. here I am not surprised such poor quality is acceptable.

#55 GOLGO13

GOLGO13

    Fly Me to the Moon

  • *****
  • Posts: 6,955
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 31 August 2020 - 07:46 AM

Jay, are you seeing this all the time or only against a bright background? I think I only see it against bright backgrounds like my garage door. I don't see anything while observing through the telescope. Or even general use in the woods. But I will try to look for it next time I have a chance.

#56 jay.i

jay.i

    Mercury-Atlas

  • *****
  • topic starter
  • Posts: 2,893
  • Joined: 11 Jun 2017
  • Loc: Minneapolis, MN

Posted 31 August 2020 - 09:32 AM

Jay, are you seeing this all the time or only against a bright background? I think I only see it against bright backgrounds like my garage door. I don't see anything while observing through the telescope. Or even general use in the woods. But I will try to look for it next time I have a chance.

As stated before, it is only in bright scenes. I do see it under heavy LP+poor transparency with my 6nm Ha filter which I was a little surprised by as the Ha filter should cut most of that LP. I think the poor transparency makes the sky lit uniformly enough that the honeycomb pattern can show itself.



#57 jay.i

jay.i

    Mercury-Atlas

  • *****
  • topic starter
  • Posts: 2,893
  • Joined: 11 Jun 2017
  • Loc: Minneapolis, MN

Posted 31 August 2020 - 09:34 AM

jay.i,

 

Your tube rocks!   I have owned over a dozen recent vintage image tubes (Gen 3 thin-film and unfilmed, white phos and green).  Given similar performance specs, Unfilmed generally outperforms thin-film every time.  The FPN on unfilmed tubes from L3 is a feature, NOT a flaw.

 

Enjoy your tube.

 

Oh, and I'm not a vendor.

What do you mean FPN is a feature? It's a byproduct of the MCP design. I'd absolutely prefer not to see a hexagonal screen in front of my images in brightly lit scenes. I would call it a flaw, despite knowing barely enough to say that I'm pretty sure there's no way to prevent it based on existing MCP design (as shown by cnoct in a previous post).



#58 GOLGO13

GOLGO13

    Fly Me to the Moon

  • *****
  • Posts: 6,955
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 31 August 2020 - 10:08 AM

As stated before, it is only in bright scenes. I do see it under heavy LP+poor transparency with my 6nm Ha filter which I was a little surprised by as the Ha filter should cut most of that LP. I think the poor transparency makes the sky lit uniformly enough that the honeycomb pattern can show itself.


Gotcha. That doesn't sound too bad to me. I would be concerned if it was under normal circumstances.

#59 Mike Lockwood

Mike Lockwood

    Vendor, Lockwood Custom Optics

  • *****
  • Vendors
  • Posts: 2,056
  • Joined: 01 Oct 2007
  • Loc: Usually in my optical shop

Posted 31 August 2020 - 02:59 PM

See my comet photo here for some faint FPN:

  http://www.loptics.c...n.html#July2020

 

The comet and the sky background were fairly bright.  I tend to run the gain fairly high.



#60 jay.i

jay.i

    Mercury-Atlas

  • *****
  • topic starter
  • Posts: 2,893
  • Joined: 11 Jun 2017
  • Loc: Minneapolis, MN

Posted 31 August 2020 - 10:45 PM

Had some clear-ish skies tonight and decided to check out Sagittarius with the FS-60CB. 55mm Plossl and 67mm lens show up tomorrow after UPS screwed up twice (continuing their trend of worst delivery company ever) so I couldn't go afocal to get some brightness. Despite that, running at native f/5.9, I got some nice views with the 6nm Astronomik Ha filter (given my Bortle 8 skies).

 

Curiously enough, I was finally able to see some honeycomb FPN looking through the telescope, at probably 75% gain. Sagittarius was fairly low in the sky and there were some scattered clouds, so the sky was not dark, just to make it crystal clear. You can slightly see the pattern in this image taken with my Pixel 3a in Night Sight mode. Note the glare arc from street lights/the moon/something around the area.

 

The FPN didn't bother me in the instances that I could see it, but it was noticed. Normal? Maybe.

Attached Thumbnails

  • apartment_m8-m20_ohheytheressomehoneycombeh.jpg

Edited by jay.i, 31 August 2020 - 10:54 PM.


#61 jdbastro

jdbastro

    Viking 1

  • *****
  • Posts: 825
  • Joined: 18 Aug 2007
  • Loc: Commie Calif.

Posted 01 September 2020 - 12:11 AM

It's normal.  Relax and enjoy your tube.


  • cnoct likes this

#62 Tyson M

Tyson M

    Fly Me to the Moon

  • *****
  • Posts: 6,072
  • Joined: 22 Jan 2015
  • Loc: Canada

Posted 01 September 2020 - 02:05 PM

This thread has been informative with an aspect I didnt know existed with NV devices.  Good to know, thanks J! 


  • jay.i likes this

#63 jay.i

jay.i

    Mercury-Atlas

  • *****
  • topic starter
  • Posts: 2,893
  • Joined: 11 Jun 2017
  • Loc: Minneapolis, MN

Posted 01 September 2020 - 03:07 PM

This thread has been informative with an aspect I didnt know existed with NV devices.  Good to know, thanks J! 

Glad to hear it Tyson! I didn't know about it either despite my research before buying (if I did, I forgot, because people don't talk about it much) which is why it's been a bit of a difficult thing to accept. If I had expected it, maybe I would feel differently. Maybe I would have requested a tube from a different manufacturer whose tubes don't show it as prominently as L3. My goal here was to see if my tube was defective, improve my own understanding, and help others along the way if possible. Hopefully others learn from this as well.

 

I sent my photos to Todd from UNV today, and he responded saying they are all normal. He wants to know what I see under clear skies "without any light pollution". I told him that there is basically no one who can get away from LP entirely, and that even though I am moving to a slightly darker location soon, I won't be getting to truly dark skies with any regularity, and so my device's performance under typical observing conditions is important to me. I think that would be true for every user of a product (to anticipate its performance under typical operating conditions for that user).

 

In that case, I'd recommend that anyone who plans to observe regularly under bright skies (brighter than Bortle 6 I'd say) should explore the possibility of getting a tube from manufacturers other than L3, like Elbit or Photonis, so as to avoid prominent FPN. My tube has some great stats, but the FPN negates them in some scenarios where they mean less (high light = low EBI/high SNR doesn't matter as much). Had I known this before, and had I been able to find a filmless WP tube from another manufacturer that had similar stats, for the same money, in a MOD3 housing, I would have bought that. But hindsight is 20/20, and tubes like mine don't seem to come around every day, so I think I oughta be happy.


  • Tyson M likes this

#64 GOLGO13

GOLGO13

    Fly Me to the Moon

  • *****
  • Posts: 6,955
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 01 September 2020 - 07:10 PM

Jay,

 

I just did an indoor test (it's cloudy outside). I didn't see the pattern when it was very dark in the basement until I used the IR feature. Then I saw it pretty clear on drywall that's not painted (bright white). So the brighter the situation with the gain turned up, the more I would see the pattern.

 

I don't remember seeing this much outside of very bright situations, but I don't look for it too much. 

 

I could see maybe in a situation with a very bright sky, no filter, gain way up,  this could show up. I also only remember seeing this at 1x. My skies are Bortle 6 I think the best SQM I have had is 19.4. 

 

Is this occurring with every filter type? HA, Long pass, etc?



#65 GOLGO13

GOLGO13

    Fly Me to the Moon

  • *****
  • Posts: 6,955
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 01 September 2020 - 07:58 PM

I tried to take a picture of it, but it didn't come out. Visually I wouldn't say it was extremely obvious all over the entire FOV. More spots had some more obvious than others. I can say I don't remember seeing this at 1x under my sky. But I will try to look for it next time. I do have areas of my sky that are quite washed out.

 

It maybe worth trying another tube, but certainly I think it is possible to see what you are seeing in bright situation against a bright object at close range. Just seems like maybe yours is a bit more obvious than others.

 

My tube type is filmless WP 11769 and specs below:


Edited by GOLGO13, 01 September 2020 - 10:23 PM.


#66 John Vogt

John Vogt

    Mariner 2

  • *****
  • Posts: 253
  • Joined: 26 Oct 2005

Posted 01 September 2020 - 08:29 PM

Hi All,

 

This has been a most enlightening and informative thread.  I also was not aware of FPN until this

discussion ensued.

This puts me into something of a quandary, I had ordered a MOD3C ASTRO from UNV back in May but because I had requested a tube with higher gain (2500) Todd had indicated it would take some months to get one with that spec. I have yet to hear from them as to the status of my order and was about to call him but at this point I'm not sure how I should proceed.

 

I'm not familiar with the different brand tubes available and as Jay mentioned maybe I should request a different brand tube to avoid the FPN issues being discussed. That is if UNV can even get a different brand tube to minimize this issue and also will it be able to match the specs of the L3 tubes most are using?

 

Last Sept at Cherry Springs I used Al Nagler's TNV/PVS-14 attached to my 32" for an entire evening and did not see any of these issues. Of course that site had an SQM of 21.7 or better, not like the Bortle 6-7 or worse skies I have at home.

 

What's a fella to do?

 

John



#67 jay.i

jay.i

    Mercury-Atlas

  • *****
  • topic starter
  • Posts: 2,893
  • Joined: 11 Jun 2017
  • Loc: Minneapolis, MN

Posted 01 September 2020 - 10:19 PM

Jay,

 

I just did an indoor test (it's cloudy outside). I didn't see the pattern when it was very dark in the basement until I used the IR feature. Then I saw it pretty clear on drywall that's not painted (bright white). So the brighter the situation with the gain turned up, the more I would see the pattern.

 

I don't remember seeing this much outside of very bright situations, but I don't look for it too much. 

 

I could see maybe in a situation with a very bright sky, no filter, gain way up,  this could show up. I also only remember seeing this at 1x. My skies are Bortle 6 I think the best SQM I have had is 19.4. 

 

Is this occurring with every filter type? HA, Long pass, etc?

I just got in from a session with my TV 55/67 Plossl setup, finally doing afocal, using my EON 120, and I saw it with the Astronomik 642nm IR pass filter but not with the 6nm Ha filter, at least I don't think so. Considering the 642 lets a decent amount of light in, I'm not super surprised, but even at 30deg altitude I saw it. Just measured the skies - SQM 18.67 near Sagittarius (about 15-20deg up) and SQM 19.03 at maybe 65-70 degrees to the south. There's a full moon out which definitely isn't helping, but there's no glare in the image or anything. It's just bright enough for me to see a little FPN. It didn't really annoy me, I just said "oh hey FPN what's up nice to see you again" and kept scanning for cool stuff. I've stumbled into a few globs and nebula in Sagittarius and have spent my time looking at the clusters and asterisms I find, so the FPN hasn't been a bother. So that's nice.

 

With my ENVIS and 50mm Computar, whether I use no filter, 7nm Ha, 6nm Ha, 685nm IR pass, or 642nm IR pass, under my home skies, I have no issue seeing FPN at 50% gain. The cleaner image at medium gain makes it easier to see than at higher gain where scintillation sort of lowers perceived resolution so I don't see the FPN as much.

 

I don't think mods want us sharing all tube specs at once (to be safe than sorry with ITAR) but my tube is only slightly better than yours in all specs (72 res is the biggest possibly relevant difference I'd say). Is yours made by L3 or Elbit or someone else?



#68 GOLGO13

GOLGO13

    Fly Me to the Moon

  • *****
  • Posts: 6,955
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 01 September 2020 - 10:24 PM

OK...I took the specs out...but at least you could see what it looked like.

 

I don't know who made mine, but some of the other folks here should know by the model.



#69 jay.i

jay.i

    Mercury-Atlas

  • *****
  • topic starter
  • Posts: 2,893
  • Joined: 11 Jun 2017
  • Loc: Minneapolis, MN

Posted 01 September 2020 - 10:40 PM

Here's a phone shot (Pixel 3a, Night Sight) of M8 and M20 using my 6nm Astronomik Ha filter with my EON120 + 67Plossl + 0.75x reducer. Should be around 10x and f/2.2 effective. Pretty incredible view even without the long exposure phone shot! You can see some FPN in the photo, but it was almost completely undetectable visually.

Attached Thumbnails

  • eon120-67plossl-m8-m20.jpg

  • moshen and Tyson M like this

#70 GOLGO13

GOLGO13

    Fly Me to the Moon

  • *****
  • Posts: 6,955
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 02 September 2020 - 11:35 AM

I do see it in your picture. Not sure if anyone else is getting that in their pictures. I don't believe I've seen it in many pictures on the site here. At least not too often.

 

 I don't remember seeing this in astronomy use or pictures. However, I am not great at taking the pictures, but I did have some recent fairly good ones.

 

I just looked at many old pictures and some were taken with the 6 inch F4 reduced quite a bit...I don't see anything, but then again, I didn't see it in the photos I just took against a wall where I did see it visually. So maybe my camera is just not picking it up.

 

Just trying to help out here. Is this a possible phenomenon, yes. Should it be as obvious as it appears your situation is? That's hard to say. I just went in my bathroom which only had light coming in from under the door a little. With the gain all the way up I can make out a little bit of this on the white toilet. It's much more obvious when I use the IR. Now that I'm looking for it I think I am seeing it a bit more. 

 

When I observe through the scope, I usually have the gain turned out nearly all the way. I usually put it on full, then dial it back just a small amount. 

 

 Since you are very early in the process with the vendor, I'd think it would be reasonable to try another unit out to see if it's different. Since our specs were almost the same, I'd think we could rule out this being spec specific. But I would say from my experience yes this is possible. I don't really find it distracting but I don't think I'm seeing it astronomically. 

 

I'm also interested in the factor of the speed. Because I know for me I tend to see this more when using the Envis lens than I do through the scope. I usually use prime focus and use the .7 reducer. So F2.8 in my 6 inch F4. Sometimes I combine afocal with the 40mm plossl and the .7 reducer. Which I believe is probably giving me a .5 reduction and probably F2 like you talked about above. So maybe the brighter the image the more likely to see it. 

 

I would also guess the filters cutting some light may help out a bit.

 

Hopefully this all helps :) ... If your unit is like mine I've been quite happy with it and this feature has not been much of a concern astronomically. 



#71 jdbastro

jdbastro

    Viking 1

  • *****
  • Posts: 825
  • Joined: 18 Aug 2007
  • Loc: Commie Calif.

Posted 02 September 2020 - 01:38 PM

... Had I known this before, and had I been able to find a filmless WP tube from another manufacturer that had similar stats, for the same money, in a MOD3 housing, I would have bought that. But hindsight is 20/20, and tubes like mine don't seem to come around every day, so I think I oughta be happy.

There is only ONE manufacturer of unfilmed tubes.  And that is L3 (or whatever they're calling themselves these days).  Given a thin-filmed tube with similar specs to an unfilmed, the unfilmed produces a crisper, less 'filmy/hazy' view with fast optics, every time.  You have a great tube.  If you go with a thin-filmed, you'll lose image contrast with fast optics.



#72 Astrojedi

Astrojedi

    Fly Me to the Moon

  • *****
  • Posts: 5,770
  • Joined: 27 May 2015
  • Loc: SoCal

Posted 02 September 2020 - 01:41 PM

There is only ONE manufacturer of unfilmed tubes.  And that is L3 (or whatever they're calling themselves these days).  Given a thin-filmed tube with similar specs to an unfilmed, the unfilmed produces a crisper, less 'filmy/hazy' view with fast optics, every time.  You have a great tube.  If you go with a thin-filmed, you'll lose image contrast with fast optics.

I don’t have as much experience as you in NV so looking to understand this better. Why do you say you will lose contrast when using thin filmed tubes with fast optics?



#73 Gavster

Gavster

    Apollo

  • *****
  • Posts: 1,135
  • Joined: 07 Mar 2014

Posted 02 September 2020 - 02:58 PM

There is only ONE manufacturer of unfilmed tubes.  And that is L3 (or whatever they're calling themselves these days).  Given a thin-filmed tube with similar specs to an unfilmed, the unfilmed produces a crisper, less 'filmy/hazy' view with fast optics, every time.  You have a great tube.  If you go with a thin-filmed, you'll lose image contrast with fast optics.

As you also have a photonis intens tube, I’d also be interested to hear your thoughts on how this compares to your l3 and high spec thin filmed tubes both with and without ha filters. I have seen previous comments that thin filmed tubes show tighter stars than unfilmed - do you agree with this? 


  • Joko likes this

#74 jdbastro

jdbastro

    Viking 1

  • *****
  • Posts: 825
  • Joined: 18 Aug 2007
  • Loc: Commie Calif.

Posted 02 September 2020 - 03:05 PM

I don’t have as much experience as you in NV so looking to understand this better. Why do you say you will lose contrast when using thin filmed tubes with fast optics?

I have put a thin-filmed up against several unfilmed tubes at 1X with f1.2 objectives.  The TF tube had higher specs than the either unfilmed.  The sky in the unfilmed tubes looked crisp.  The TF tube appeared to show a faint milky haze compared to the unfilmed.

 

When you run with slower optics, the difference becomes far less obvious.


  • Joko likes this

#75 jdbastro

jdbastro

    Viking 1

  • *****
  • Posts: 825
  • Joined: 18 Aug 2007
  • Loc: Commie Calif.

Posted 02 September 2020 - 03:09 PM

As you also have a photonis intens tube, I’d also be interested to hear your thoughts on how this compares to your l3 and high spec thin filmed tubes both with and without ha filters. I have seen previous comments that thin filmed tubes show tighter stars than unfilmed - do you agree with this? 

Without Ha filters, the unfilmed showed fainter stars at low power (< 10X).  I don't recall the results with Ha.  Generally, INTENS tubes lack the PR (PCR) of either good performing thin-filmed or unfilmed tubes.  PR turns photons into electrons.  You always want as much of that as you can get in an image intensifier.  Photonis refuses to publish PR for their tubes.  Why is that, I wonder?


  • Joko and cnoct like this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics