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NVD Comparison and more...

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#51 Peregrinatum

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Posted 02 March 2020 - 02:03 PM

Just beautiful images Ray, you have the best NV phone images I have seen.


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#52 GeezerGazer

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Posted 04 March 2020 - 04:49 AM

I wanted to finish test photos for the tube comparison as stated at the end of post #49.  So I was out tonight for 30 minutes just after 7 p.m. in the half moon at zenith to take 4 images, two through the Mod 3C white phosphor and two through the Micro green phosphor.  Again, I was pretty impressed with how well the 12 yr. old tube performed.  I aimed at two subjects, the first 2 images were taken with the Mod 3C WP tube, of IC 1848, the Soul Nebula, using my ES 208 w/ASA .73x reducer, 7nm filter; the second target was IC 434 with Barnard 33 (HH).  Then I switched to the Micro with green phosphor tube and re-acquired the same targets... using exactly the same settings.  

 

You might wonder where the photos are.  Well, I don't feel like writing a full-on observing report to put them in this post.  So you can see both comparison photos with all the settings in my gallery images:  

https://www.cloudyni...oto-of-ic-1848/

They are the first two images at the top of the page.  Just click on them to open them.  I'll leave them posted for a month or two.  There are no photos in this post, so I think I'm within the rules.  

 

Now, remember that I wanted to show 3 things.  First, the image of IC434 which includes Alnitak, reveals the difference in halo between these tubes.  Visually, the Mod 3C WP tube showed a bright, but smaller halo around Alnitak; the photo shows a larger, but much fainter secondary halo.  The Micro green phosphor F9800 tube showed a much larger and brighter halo visually, demonstrated in the photo comparison.  This bright halo, however, is smaller than the dim secondary halo revealed through the Mod 3C.  I did not see the Mod 3C secondary halo at all visually at the ocular... only in the photo does it appear.  

 

The second thing I wanted to show was star comparison with the best focus that I could achieve.  In both (all 4) comparison photos, and visually, the stars (other than the brightest which show halo) remain tight through both intensifiers.  

 

Finally, I wanted to photograph for brightness comparison using the same settings for images through both tubes.  So that's what I did on both subjects.  The settings are shown under the images.  I am pretty sure that when the previous image of the Rosette was taken, the gain on the Mod 3C must have been set lower than full gain.  When I took the current images, I made sure that the gain was fully on.  As a result, the images are VERY close in brightness.   

 

Overall, with the exception of differences in halo around the brightest stars, these intensifier tubes seem pretty equal, in spite of their significantly different specifications.  The Mod 3C L3 WP tube may reveal contrast, especially in very dim subjects a little better, but it is quite subtle.  The Micro has no gain control, so it is always at maximum gain.  But the aperture ring on the 50mm Computar f:1.3 lens works just as well as a manual gain on the Mod 3C.  This works well with any of my camera lenses, but when used in prime focus with a telescope, there is no aperture ring.  Narrow band-pass and long pass filters do tone down the brightness through the Micro to a large extent.  

 

The only thing left for me to test between these two intensifiers is a very narrow band-pass H-a filter.  For that, I'll wait until after full moon.  I'm expecting a new filter about that time.  

Clear Skies.  



#53 starzonesteve

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Posted 04 March 2020 - 09:56 AM

Thanks for taking the time and effort to do this. These two photos are very close, closer than the previous comparison, imo. I very slightly liked the green phosphor image better. Mostly it contrasts the nebulosity just a little bit more in relation to the background stars than the white phosphor. The difference is extremely subtle. They are both very clean images.


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#54 Jeff Morgan

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Posted 04 March 2020 - 11:41 PM

Finally, I wanted to photograph for brightness comparison using the same settings for images through both tubes.  So that's what I did on both subjects.  The settings are shown under the images.  I am pretty sure that when the previous image of the Rosette was taken, the gain on the Mod 3C must have been set lower than full gain.  When I took the current images, I made sure that the gain was fully on.  As a result, the images are VERY close in brightness.   

 

Overall, with the exception of differences in halo around the brightest stars, these intensifier tubes seem pretty equal, in spite of their significantly different specifications.  The Mod 3C L3 WP tube may reveal contrast, especially in very dim subjects a little better, but it is quite subtle.  The Micro has no gain control, so it is always at maximum gain.  But the aperture ring on the 50mm Computar f:1.3 lens works just as well as a manual gain on the Mod 3C.  This works well with any of my camera lenses, but when used in prime focus with a telescope, there is no aperture ring.  Narrow band-pass and long pass filters do tone down the brightness through the Micro to a large extent.  

 

Interesting, when I shoot photos I also turn down the gain, thinking it will "defeat" scintillation. It would seem that notion is mistaken.

 

Impressive work. I would agree, very close. When you have to do A/B A/B for a few minutes to see the difference - both have to be declared "Winner".

 

So do you like white or green?

 

Very slightly more nebula or very slightly sharper stars?

 

Which tube can you get soonest?


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#55 GeezerGazer

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Posted 14 March 2020 - 02:14 AM

Interesting, when I shoot photos I also turn down the gain, thinking it will "defeat" scintillation. It would seem that notion is mistaken.

 

So do you like white or green?

 

Jeff, turning the gain down is not necessary when using long exposure mode in NightCap.  It averages any scintillation out of the image.  I never turn down the gain on the NVD.  Even on the brightest subject you can find in the night sky, first reduce the ISO to it's lowest setting (ISO 24 on an XR) and if it is still too bright, shorten the exposure time.  The lower the ISO, the less noise you'll see; the faster your exposure, the more images are averaged in a given number of seconds.  So keep that gain on full when taking an image.  

 

I like both, green and white phosphor.  If I don't like an image color, I usually change them to B&W (one click editing tools within the iPhone photos app or by using Snapseed photo editing app) before I put them into my computer library.  No post processing for photos here in the forum.  But I use these same apps to crop, rotate, etc. before posting here.  The NightCap camera app also has a B&W setting so that you can take the image in B&W, therefore avoiding any post processing altogether... I frequently use that option.



#56 GeezerGazer

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Posted 14 March 2020 - 02:22 AM

The 3.5nm Antlia H-a filter I ordered has arrived, but of course, a storm is rolling in.  So when it clears, I'll give it a try for visual use in mono and bino mode.  I'm thinking it will be too aggressive to use for imaging with my iPhone, but for visual, it might work well. I'll test this filter for visual mono/bino and imaging and post back when finished... last test.  



#57 Gavster

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Posted 14 March 2020 - 02:41 AM

Jeff, turning the gain down is not necessary when using long exposure mode in NightCap.  It averages any scintillation out of the image.  I never turn down the gain on the NVD.  Even on the brightest subject you can find in the night sky, first reduce the ISO to it's lowest setting (ISO 24 on an XR) and if it is still too bright, shorten the exposure time.  The lower the ISO, the less noise you'll see; the faster your exposure, the more images are averaged in a given number of seconds.  So keep that gain on full when taking an image.  

 

I like both, green and white phosphor.  If I don't like an image color, I usually change them to B&W (one click editing tools within the iPhone photos app or by using Snapseed photo editing app) before I put them into my computer library.  No post processing for photos here in the forum.  But I use these same apps to crop, rotate, etc. before posting here.  The NightCap camera app also has a B&W setting so that you can take the image in B&W, therefore avoiding any post processing altogether... I frequently use that option.

Interesting Ray. I think it’s slightly different when I take 10-30 nv exposure shots with my huawei since there is no averaging involved and so scintillation is something to try to avoid to get a cleaner image. Keeping iso as low as possible remains key for a nicer result. The full gain on my harder gen 3 is much brighter/noisier than my photonis 4g so I generally don’t use full gain for the harder when observing whereas photonis I’m often at or close to full gain. Using very narrow hand filters such as a 3nm does mean the gain should be turned up more than say a 685 or 642 filter.


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#58 chemisted

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Posted 14 March 2020 - 12:24 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!

This will be brief as I have only been able to try this arrangement during full moon.  The two devices were equipped as described above and hand held to merge the two views together.  My observation of Orion pretty much duplicated Ray's description where both devices in binocular mode gave the best view of Barnard's loop.  I will post again when a dark and clear night arrives.

 

I am really impressed with the Fujinon 50mm lens. The focusing and aperture rings are super smooth. It has a 49mm filter thread on the front to which I applied one layer of black electrician's tape and screwed in my 2" 12nm filter.  This works very well and is almost a press fit that allows easy insertion and removal.  For the NVD Micro I pulled out a 50mm f/1.8 E-series lens from my collection.  This is a lot smaller and lighter than the standard lens.  It was joined to the Micro with a Nikon to c-mount adapter containing the 7nm filter.  As Ray experienced, even though the two sides of the binocular are very different the view was very much like using a standard binocular - only with the night vision advantage.



#59 GeezerGazer

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Posted 14 March 2020 - 11:25 PM

Interesting Ray. I think it’s slightly different when I take 10-30 nv exposure shots with my huawei since there is no averaging involved and so scintillation is something to try to avoid to get a cleaner image. Keeping iso as low as possible remains key for a nicer result. The full gain on my harder gen 3 is much brighter/noisier than my photonis 4g so I generally don’t use full gain for the harder when observing whereas photonis I’m often at or close to full gain. Using very narrow hand filters such as a 3nm does mean the gain should be turned up more than say a 685 or 642 filter.

That definitely makes sense to me for visual use.  Does scintillation show up in your long exposure Huawei images if you use full gain?  Since the iPhone limits exposure to 1s, my gain is always turned on full, and I do rely on NightCap's averaging to eliminate image noise caused by scintillation.  For visual use, I'm thinking that the 3.5nm filter will also require full gain.  I'll look at that issue when I test.  Thanks



#60 GeezerGazer

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Posted 14 March 2020 - 11:54 PM

This will be brief as I have only been able to try this arrangement during full moon.  The two devices were equipped as described above and hand held to merge the two views together.  My observation of Orion pretty much duplicated Ray's description where both devices in binocular mode gave the best view of Barnard's loop.  I will post again when a dark and clear night arrives.

 

I am really impressed with the Fujinon 50mm lens. The focusing and aperture rings are super smooth. It has a 49mm filter thread on the front to which I applied one layer of black electrician's tape and screwed in my 2" 12nm filter.  This works very well and is almost a press fit that allows easy insertion and removal.  For the NVD Micro I pulled out a 50mm f/1.8 E-series lens from my collection.  This is a lot smaller and lighter than the standard lens.  It was joined to the Micro with a Nikon to c-mount adapter containing the 7nm filter.  As Ray experienced, even though the two sides of the binocular are very different the view was very much like using a standard binocular - only with the night vision advantage.

So you are using a Micro with 50mm camera lens and a Collins I cubed with a Fujinon CCTV 50mm lens, a 12nm H-a on one and 7nm on the other... merging with no problem at 2x and 20° FoV.  I am amazed that these combinations can perform as well as they do and that our brain/eyes can accommodate the differences.  But the result is really quite wonderful.  Of course, we are supposed to have clouds and rain for the next 8 days!  But if I can find a hole in the clouds one night, I'll try to do a test with the 3.5nm:
1.  Visually in mono with white then green phosphor, using gain adjust on Mod3.
2.  Visually in Bino mode with a 7nm on the opposite NVD.
3.  Visually in Bino mode but switch filters on the NVDs.
4.  One image each through Mod3 and Micro with 3.5nm H-a filter.



#61 Gavster

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Posted 15 March 2020 - 12:52 AM

That definitely makes sense to me for visual use.  Does scintillation show up in your long exposure Huawei images if you use full gain?  Since the iPhone limits exposure to 1s, my gain is always turned on full, and I do rely on NightCap's averaging to eliminate image noise caused by scintillation.  For visual use, I'm thinking that the 3.5nm filter will also require full gain.  I'll look at that issue when I test.  Thanks

At full gain the exposure time is lower but the image doesn’t look as sharp. As I can go up to 30 secs exposure at lower gain (in fact I rarely go to 30 secs since the background becomes too bright) I tend to just use the same gain as I’m visually observing with.



#62 GeezerGazer

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Posted 21 March 2020 - 12:55 AM

I received a 2" Antlia 3.5nm H-a filter ($319), so last night, under poor seeing, poor transparency and 90+% humidity, with high clouds, I couldn't see much from my red zone LP home with an LED streetlight 50' away! 

 

Tonight, seeing and transparency were average, no clouds, and humidity was in the 50% range.  With a 7nm filter on the Mod 3C and the 3.5nm on the Micro, H-a was very visible in binocular mode.  I switched filters between the two NVDs and found it didn't make too much difference which NVD was used with which filter.  The merged image remained about the same.  

 

What was the image like you might ask... I believe it was the first time I've ever seen Barnard's loop from home using my NVDs visually.  The 3.5nm filter brightens (increases contrast) H-a much more than the 7nm.  Since the bandwidth is 1/2 as wide on the 3.5nm, I suppose I could guess that it was twice as bright, but I didn't think it was quite that much difference... maybe.  Brightness is a hard thing for me to judge.  But when I'd close one eye and look through one NVD at a time, it was very clear that the 3.5nm produced much greater contrast to reveal H-a subjects.  

 

When I looked through the NVD with the 7nm filter, I could barely detect Barnard's Loop and only when moving the 2x objective around could I actually tell that there was something slightly brighter than the background sky.  Whereas when I looked through the 3.5nm with one eye open, the brightest, upper part of Barnard's Loop was very clearly there with direct vision... along with M42, the Flame, and above, a fainter Angelfish.  

 

I turned to the Rosette to compare the two filters.  The 7nm showed the Rosette as an evenly lit smudge of H-a.  The 3.5nm showed it as being brighter, but revealed the darker core and some dark lines that help form the rose petals.  I could not see the star cluster in the core, but there were a couple of stars within the nebula that were not attenuated.  Above the Rosette, I could just make out the much fainter but larger H-a region dubbed the Fox Fur Nebula Sh2-273 (NGC 2264).  

 

Last, I drifted over to the Flaming Star in Auriga and could easily see its shape along with Sh2-236 next to it.  

 

I stared for a while and then went back in the house... only to turn around and go back out for another look... no, it was all still there!  Actually I went back out to check scintillation between the images produced by the two NVDs with the 7 & 3.5nm filters.  I was still pretty excited by this new experience, but during my first view I hadn't even noticed if there was scintillation present in the merged binocular image.  So this second trip out was to actually look for it.  Minor scintillation was present at about the same degree through both filters.  Looking with one eye at a time and switching back and forth, I really could not see a significant difference of scintillation between the NVDs; and it was at a level that was definitely not annoying.  It was there, but it just wasn't bad enough to seem like a problem or annoyance visually.  

 

So here is the BEST discovery I made about using different H-a filters in binocular mode.  The merged image that I saw using both eyes shows the H-a subject just as bright and contrasty as I could see it through the narrower band filter when using one eye.  WHAT? Yea, the eye/brain thing, picks the brighter image and merges that with the dimmer/less contrasted image from the wider band filter.  Do I really need two 3.5nm filters if I'm already getting the contrast advantage from just one?

 

So here, I need a confirmation from Gavster.  I'll contact him for a test... he has dual 3nm H-a filters that he normally uses on his NV Binos, but he also has a 5nm and I think 6nm that he could put on one side of the binocular to test my results.  I'd like to see if one 3nm filter and one 6nm filter produces the same kind of image as two 3nm filters.  He's the only one I know who has all of 'em.  


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#63 PEterW

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Posted 21 March 2020 - 10:30 AM

Gav uses a harder and Photonis tubes, so you see slight differences even with the same filters on the front. With either eye things are not too easy to spot, two eyes and they just jump out at you. Great if both eyes see the same, but the “wetware” doesn’t care if they’re slightly different! Another member of the NVbin crowd!

Peter
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#64 Jeff Morgan

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Posted 21 March 2020 - 12:32 PM

Do I really need two 3.5nm filters if I'm already getting the contrast advantage from just one?

 

So you "saved money" by getting a second NVD!

 

How is the egde of field performance, any darkening?


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#65 GeezerGazer

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Posted 21 March 2020 - 03:18 PM

So you "saved money" by getting a second NVD!

 

How is the egde of field performance, any darkening?

Well, with the Micro and the 3.5nm Antlia filter, cost totals $1845 with the 2x objective lenses.  So it did cost a bit to make my Mod 3C able to serve double duty.  Time will tell if it was worth the expense.  As you know, I tend to spend most of my observing time with my phone hanging on the NVD ocular.  But I have to tell you, this NVD binocular is a different experience; one that refreshes my interest in observational NV astronomy.  How long I will be infatuated with it is an unknown.  I have yet to try it from a dark site which should reveal much more detail than what I can see at home.  I'm looking forward to that experience.  

 

Because my little bino-adapter is made for my IPD, I can't really share the experience with others.  But I have found that pulling the oculars up to 1" away from my eyes, the image can be seen by others within a wider range of IPD.  Not perfect, but not terrible because the image is bright enough from the NVDs.  

 

Good question about EoF darkening.  Last night, I did not pay attention to EoF darkening from band shift or vignetting... too enamored by the central image I was seeing.  I'll try to do that next week after our current storms pass.  I don't think there will be any vignetting; the 50mm f:1.3 CCTV C-mount objective lenses have a smaller clear aperture (46mm filter threads) than the 2" filters.  I suspect there will be band shift, and I'll try to estimate how much is present with both the 7nm and 3.5nm filters using these specific objective lenses.  My past experience with band shift has shown that the faster the optical focal ratio is, the more problematic band shift becomes; it's dependent on how oblique the angle of light encounters the edge of the optical system... so largely depends on the curvature of the objective field lens, just behind the first-surface filter.  

 

I've asked Gavster to conduct a test, to see if he detects a difference in overall H-a contrast when using two filters of different band pass widths, compared to two identical filters.  I also asked, when he tries the two different filters, to switch them on the NVDs to see if there is a difference concerning his dominant eye receiving or not receiving the higher contrast image.  I was wondering if my dominant eye played a part in how my brain merged the images for different NVDs with different filters.  This is all very new to me and my curiosity begs answers. 




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