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Night vision with a 16 inch dob

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#1 Gavster

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Posted 24 August 2019 - 12:14 PM

 My favourite NV scope is I think my C11 which has given me some fantastic views with a 0.75x reducer and 55mm plossl (effective system speed f3.3).

However, I had a dose of aperture fever last year and ordered a 16 inch goto dob manufactured by sky vision in France.

It turned up late last year and I as it was my first dob I was a bit shocked by the size and bulk of it.

I had a couple of goes with it but struggled with the coma corrector spacing (I had the Es one) and was a bit disappointed with the nv views it gave since the edge stars were pretty horrible.

The scope got mothballed for a few months.

Then events happened which enabled me to take it to my dark sky site for further testing. I also purchased a Televue paracorr which increase the f ratio of the scope a little but enable me to be more confit about getting the coma corrector working properly.

I set the scope up carefully last night following the paracorr instructions and with an ethos in non nv mode the views looked good across the field of view. However once I moved to the nv monoculars and 41mm panoptic the star shapes at the edge weren’t great. I was disappointed. I checked the paracorr instructions and I’d done everything right. I think checked the collimation again and it was a bit out. After adjusting and redoing collimation twice I eventually got decent stars with the panoptic.

Are nv monoculars more sensitive to non-accurate collimation than normal glass eyepieces??

Anyway after a few hitches with the goto setup I eventually got everything working well. By this time it was getting very late so I only managed a few objects in Cygnus.  But they looked rather nice - a step up in resolution to my c11 phone images I think and the visual views are also noticeably better.

Here is the Pac-man, eastern veil and crescent nebula (25 secs, 20 secs and 20 secs exposure time)

I’m now looking forward to using this scope again despite it taking materially longer for me to setup compared to the c11.

 

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#2 descott12

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Posted 24 August 2019 - 12:48 PM

Nice images. Thanks for the post. Those are probably the clearest/best NV images I have seen posted on CN. But I am still a bit confused about the benefit of NV and what you actually can see with your eye in realtime. I do mostly EAA so I appreciate what one can see with a short stack. 

 

My interest in NV, and what I perceive to be it's strongpoint, is to be able to drop all computers and power supplies and cameras and just enjoy the view. So can you see anything close to those images live? If you can see something similar to those images, then I think NV would be well worth the cost. But if not, I struggle to see the real benefit over normal EAA which is in color and can produce probably better images for a smaller investment.  Thanks in advance for any clarification.



#3 Gavster

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Posted 24 August 2019 - 12:55 PM

Nice images. Thanks for the post. Those are probably the clearest/best NV images I have seen posted on CN. But I am still a bit confused about the benefit of NV and what you actually can see with your eye in realtime. I do mostly EAA so I appreciate what one can see with a short stack. 

 

My interest in NV, and what I perceive to be it's strongpoint, is to be able to drop all computers and power supplies and cameras and just enjoy the view. So can you see anything close to those images live? If you can see something similar to those images, then I think NV would be well worth the cost. But if not, I struggle to see the real benefit over normal EAA which is in color and can produce probably better images for a smaller investment.  Thanks in advance for any clarification.

Yes the live eyepiece views are very similar to the phone images. I take the phone images for quick visual record of my nv observing sessions.


Edited by Gavster, 24 August 2019 - 12:56 PM.


#4 descott12

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Posted 24 August 2019 - 01:03 PM

Yes the live eyepiece views are very similar to the phone images. I take the phone images for quick visual record of my nv observing sessions.

Well then that is VERY cool...now I just have to dig up another 4000 USD!


Edited by descott12, 24 August 2019 - 01:46 PM.

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#5 Eddgie

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Posted 24 August 2019 - 01:23 PM

Dave,

 

I would say that the images you see here overstate the brightness that you would see in the eyepiece, and some of the result depends on the speed of the scope being used, but seeing the detail portrayed in these images is indeed possible with NV in the real time views.

 

I use much smaller telescopes than used to take these pictures, and I can see much of the detail (though at a smaller scale) but I don't think the view is nearly as bright as these pictures suggest. Yes, the detail is there, but it simply is not this bright.  If the eye is dark adapted though, the detail can be seen. 

 

I would though be cautious about recommending that you try it.  You currently get color, and with long integration times, you get detail that is fairly free of noise.  With NV, the view is monochrome and for these kinds of objects, there is noise, which the images on the web tend to conceal.  Yes, the detail is there, but it is monochrome and with heavy filters, it can be both dim and noisy.   

 

Here are some examples that shows what the real time view can look like:

 

https://www.youtube....?v=I7Paem8OSWI 

 

https://www.youtube....h?v=vQXTK56Z5UQ

 

https://www.youtube....h?v=PowjoGq07Lw

 

https://www.youtube....h?v=AO0w6AO8iWw

 

https://www.youtube....h?v=uZH2Qm7qFdc

 

https://www.youtube....h?v=uWH_2HoR6cU

 

I generally don't actively discourage people from considering NV, and I am not trying to discourage you either, but at the same time, pictures are pictures and they are almost never exact reproductions of what we actually see.  If you think you would find the noise and the monochromatic nature to be big negatives, then they probably are, and you can buy yourself an much nicer camera for what you would spend on NV gear. 


Edited by Eddgie, 24 August 2019 - 01:44 PM.

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#6 Eddgie

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Posted 24 August 2019 - 01:39 PM

Dave,

 

This particular video is a pretty fair representation of how I see the Trifid in real time using my 12" f/4.9 from a white zone. 

 

You can see that there is plenty of structure, but you can also see that the view is much dimmer than the images above would suggest (this is after all a pretty bright nebula, but the scope being used is fairly slow by NV standards, which makes the image noisier).   

 

https://www.youtube....h?v=fmTDpu3Z3kI

 

North American with a f/2 lens. Much brighter, but still noise:

 

https://www.youtube....h?v=CuCT-0FmKNg

 

Now in my 6" f/2.8, the view is much quieter and the nebula is much brighter, but the image scale is quite small.  I can see the primary lanes easily though, so I actually prefer the view in the 6" than in the 12".  

 

But the point is that depending on the surface brightness, the bandwidth of the filter being used, and the speed of the scope, I would say that the real time view will generally be quite a bit dimmer and far nosier than the above images suggest. 

 

Now when running no filter, the image is very bright and the noise is almost invisible. Often the camera used is nosier than the image in the tube...

 

https://www.youtube....h?v=9hiFCMaTPT0

 

I just don't want to see a dis-service done here. I love love love night vision, but for someone that is imaging, I think that maybe setting a very realistic expectation level is called for when a $4500 investment is at hand. 


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#7 descott12

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Posted 24 August 2019 - 01:49 PM

Thanks Eddgie for the posts. That puts it all in perspective. NV is definitely interesting...I will try to hook up with my local club and see it in action first.



#8 Gavster

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Posted 24 August 2019 - 02:39 PM

Dave,

 

This particular video is a pretty fair representation of how I see the Trifid in real time using my 12" f/4.9 from a white zone. 

 

You can see that there is plenty of structure, but you can also see that the view is much dimmer than the images above would suggest (this is after all a pretty bright nebula, but the scope being used is fairly slow by NV standards, which makes the image noisier).   

 

https://www.youtube....h?v=fmTDpu3Z3kI

 

North American with a f/2 lens. Much brighter, but still noise:

 

https://www.youtube....h?v=CuCT-0FmKNg

 

Now in my 6" f/2.8, the view is much quieter and the nebula is much brighter, but the image scale is quite small.  I can see the primary lanes easily though, so I actually prefer the view in the 6" than in the 12".  

 

But the point is that depending on the surface brightness, the bandwidth of the filter being used, and the speed of the scope, I would say that the real time view will generally be quite a bit dimmer and far nosier than the above images suggest. 

 

Now when running no filter, the image is very bright and the noise is almost invisible. Often the camera used is nosier than the image in the tube...

 

https://www.youtube....h?v=9hiFCMaTPT0

 

I just don't want to see a dis-service done here. I love love love night vision, but for someone that is imaging, I think that maybe setting a very realistic expectation level is called for when a $4500 investment is at hand. 

Eddgie,

It’s obviously subjective comparing live eyepiece with images. 

 

However, I’ve done a large amount of experimenting with different filters, eyepieces, scopes and nv monoculars. From this experimentation I’ve found that running very fast speeds (ideally f2 or lower) makes a huge difference to the actual live views. I also prefer very narrow top quality (ie chroma or astrodon) ha filters because they give significantly more contrast on nebulae. I run just below full gain to effectively remove the scintillation that the YouTube links show (I think video does exaggerate scintillation compared to the actual eyepiece views).

 

Being at a dark site (sqm 21+) also makes a massive difference compared to my normal city viewing (sqm 18.4).

 

My most recent ‘discovery’ is how much aperture ‘matters’ for nv. Last night in my 16 inch the Pelican was just so bright and detailed - I’ve never seen the pelican like that before and it shocked me. 

 

I’d say that the impact of very fast speed, large aperture, dark skies, and narrow ha filtration provide a sweet spot that gives live eyepiece views very similar (ie bright, smooth, detailed and no noticeable scintillation) to the phone images I posted above. It was a night of observing that I won’t forget.


Edited by Gavster, 24 August 2019 - 02:42 PM.

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#9 Eddgie

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Posted 24 August 2019 - 03:04 PM

Eddgie,

It’s obviously subjective comparing live eyepiece with images. 

 

However, I’ve done a large amount of experimenting with different filters, eyepieces, scopes and nv monoculars. From this experimentation I’ve found that running very fast speeds (ideally f2 or lower) makes a huge difference to the actual live views. I also prefer very narrow top quality (ie chroma or astrodon) ha filters because they give significantly more contrast on nebulae. I run just below full gain to effectively remove the scintillation that the YouTube links show (I think video does exaggerate scintillation compared to the actual eyepiece views).

 

Being at a dark site (sqm 21+) also makes a massive difference compared to my normal city viewing (sqm 18.4).

 

My most recent ‘discovery’ is how much aperture ‘matters’ for nv. Last night in my 16 inch the Pelican was just so bright and detailed - I’ve never seen the pelican like that before and it shocked me. 

 

I’d say that the impact of very fast speed, large aperture, dark skies, and narrow ha filtration provide a sweet spot that gives live eyepiece views very similar (ie bright, smooth, detailed and no noticeable scintillation) to the phone images I posted above. It was a night of observing that I won’t forget.

Everything you say is true and I cannot dispute your opinion. 

 

My concern is that someone that currently images and sees very bright and noise free images might be disappointed if they spent $4500 and found that the image in their scope was dimmer and noisier than these pictures often show.

 

If he can get a 16" f/4 dob, he can indeed get excellent views.  It is all about setting expectations and I just wanted to make sure that he got a balanced perspective.  I have used a lot of scopes with NV, and I would say that except for the very specialized ones, the noise and dimness is typically higher than many long exposure pictures show.

 

Now I think some of this is simply because if you have been using NV, you very quickly learn to simply look through the noise.

 

I recall my early days of evangelizing NV.  One of the most often listed objectives was the scintillation.   I repeatedly responded that it was easy to look past.

 

Then, we had one CN member that had an imaging background try NV, and he hated it.  He said it was just too noisy for him and thought it was a giant waste of money... 

 

So, these days, if someone that is imaging says expresses some reservations, I want to make sure that they are aware of these issues.    It is a big investment and while I agree that NV is amazing, I also want to make sure that people know that their experience can vary, and if they are used to a bright, colorful, noise free image, it may be that they will not see what many of these photos show.  I have never had NV real time views that look as bright as the ones above.  Now, I can see the detail shown in the images above, but the views using my 12" f/5 dob have not been as bright or as quiet..

 

So, with the right scope and bright targets, the view can match photos, and can even be better!   Orion is never as good in a photo as I see it in an eyepiece.  But often, my eyepiece views do not look as good as cell phone captures using long exposures. 



#10 bobhen

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Posted 24 August 2019 - 03:12 PM

Nice images. Thanks for the post. Those are probably the clearest/best NV images I have seen posted on CN. But I am still a bit confused about the benefit of NV and what you actually can see with your eye in realtime. I do mostly EAA so I appreciate what one can see with a short stack. 

 

My interest in NV, and what I perceive to be it's strongpoint, is to be able to drop all computers and power supplies and cameras and just enjoy the view. So can you see anything close to those images live? If you can see something similar to those images, then I think NV would be well worth the cost. But if not, I struggle to see the real benefit over normal EAA which is in color and can produce probably better images for a smaller investment.  Thanks in advance for any clarification.

Try this…

 

Import the images into a program that will allow you to adjust brightness (even Word is okay)

 

Now dim the brightness down about 35-40%.

 

That is “somewhat approximately” what I see live with my 210mm reflector and my Night Vision (NVD Micro) Image Intensifier.

 

Now reduce the size by about 40 – 50% and that is an estimate of what I see in my 102mm F5 refractor.

 

And I see these “easily” in “extreme” light pollution near Philadelphia PA. 

 

As to the benefits of NV…

 

Portability, no power needed, non-driven alt/az mounts can be used, as light and easy to use as an eyepiece, can be used with handheld lenses or most any telescope, extremely large objects can be observed. The views are in real-time. Cuts through light pollution. The NV experience is more closely related to visual observing. The astro video or EAA camera experience is more closely related to pure imaging.

 

I did video imaging for 15-years and have been doing NV for over 3-years. Both have advantages and disadvantages. However, if you are a “visual observer” at heart, then NV will enhance your observing experience without turning you into an imager. And besides, NV is pretty darn cool to boot.

 

Bob



#11 ngc7319_20

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Posted 24 August 2019 - 03:13 PM

 

I generally don't actively discourage people from considering NV, and I am not trying to discourage you either, but at the same time, pictures are pictures and they are almost never exact reproductions of what we actually see.  If you think you would find the noise and the monochromatic nature to be big negatives, then they probably are, and you can buy yourself an much nicer camera for what you would spend on NV gear. 

These videos are pretty interesting.  I would have to say that these views are similar to what I see by eye from a dark site (sometimes with an OIII filter if appropriate) with a medium to large Dob.  Not sure it is something I would casually invest $3k in...  Hmmm...  My interest would be primarily as a visual observing aid, rather than recording data and stacking, etc.   Maybe one difference was that these examples are taken in heavy light pollution (?) and yet they are able to see something? I am left slightly puzzled.



#12 bobhen

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Posted 24 August 2019 - 03:15 PM

These videos are pretty interesting.  I would have to say that these views are similar to what I see by eye from a dark site (sometimes with an OIII filter if appropriate) with a medium to large Dob.  Not sure it is something I would casually invest $3k in...  Hmmm...  My interest would be primarily as a visual observing aid, rather than recording data and stacking, etc.   Maybe one difference was that these examples are taken in heavy light pollution (?) and yet they are able to see something? I am left slightly puzzled.

Read my post number 10.

 

Bob 



#13 ngc7319_20

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Posted 24 August 2019 - 03:25 PM

Read my post number 10.

 

Bob 

So would you say that "cuts through light pollution" is a major reason to do NV?  You say "I see these 'easily' in 'extreme' light pollution near Philadelphia PA"...   I guess seeing faint nebula from a light-polluted backyard could be a good motivation.

 

But if you have dark skies already -- what is your sense about that situation?



#14 Gavster

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Posted 24 August 2019 - 03:37 PM

So would you say that "cuts through light pollution" is a major reason to do NV?  You say "I see these 'easily' in 'extreme' light pollution near Philadelphia PA"...   I guess seeing faint nebula from a light-polluted backyard could be a good motivation.

 

But if you have dark skies already -- what is your sense about that situation?

 

From dark sites, nv is amazing imo and a massive step up on some objects (emission nebulae specifically) (particularly with fast setups, narrow and good quality ha filters, large aperture etc )

 

I get more enjoyment and satisfaction using nv from a dark site than from a lp site.


Edited by Gavster, 24 August 2019 - 03:39 PM.


#15 spereira

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Posted 24 August 2019 - 03:44 PM

Thanks very much for this conversation, guys!  I've been contemplating an NV purchase, and this info may be what turns me away without a big loss.

 

I am a visual observer.  Hence, I am very well informed about the difference between what I can see visually with my scopes, and the excellent images that I get to see here on CN and elsewhere, be they images that result from loads of data taking, followed buy a ton of image processing, or images that result from EAA integration and no post-processing.

 

I was hoping that NV might be able to bring me there visually, but what I am seeing here indicates that the old adage "aperture matters" still holds.  The videos pointed to as examples of what you may see visually are interesting.  They are not really the "wow my pants off" images that I was hyping myself up for.  I certainly appreciate seeing what the scintillation is likely to be, but the big disappointment for me was that the scopes used seem to all be much larger than mine.  I have a TV-85, a Questar 3.5, and a Celestron C6.  f/7, f14.4, and f/10 respectively.  It seems by the example videos that you better have an 11, 14, or 16 inch aperture to be able to see things like these examples show.

 

It's starting to look like I should not be spending $4000-$5000 on NV equipment and filters that ultimately will not give me the real time visual examples that were shown.

 

If I'm going overboard the wrong way, please let me know.

 

Thanks very much for any advice - even if it's advice that I should not be going here.

 

smp



#16 Eddgie

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Posted 24 August 2019 - 03:49 PM

NV is amazing under city skies, but under dark skies, it is like being in a spaceship.

 

Now if you can see a galaxy that has a catalog size of 10 arc minutes extend to 9 arc minutes in a 14" dob, then it is not going to suddenly extend to 20 arc minutes because you use NV because if you see it at 9 arc minutes you are already seeing pretty much the full size.  NV can't create galaxy where no galaxy exists.  

 

Now, if someone was sitting next to you with an 8" dob and saw it at only being 7 arc minutes in size, if they put in a NV device, they might see it extend to the full 10 minutes.  

I routinely here that NV does not offer much advantage on galaxies, but that is because lots of people using large telescopes are already seeing these targets at near their full extension.   

 

For someone that already has and 8" scope and does not want to buy and manage a 16" telescope, then NV does indeed give a very meaningful increase in deep sky performance under dark skies. 

 

Overall though, I think using NV under dark skies is quite thrilling.   The richness of the sky is beyond my limited writing ability to describe.   I can see nebula bigger than entire constellations. I can see folds and structure in the galaxy that even long exposure images fail to capture. 

 

Now, if someone has a 20" f/3.3 dob and galaxies are their thing, then maybe they would not see that great a benefit, but I have never enjoyed dark skies as much using NV as I have used scopes up to 14".   

 

In fact, I go to dark skies more now than I ever did when I had my C14.  Even with a 6" scope, I never run out of things to see, and it is sooooo much easier than loading and unloading my C14 or 12" dob was.   
 



#17 Gavster

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Posted 24 August 2019 - 04:03 PM

Thanks very much for this conversation, guys!  I've been contemplating an NV purchase, and this info may be what turns me away without a big loss.

 

I am a visual observer.  Hence, I am very well informed about the difference between what I can see visually with my scopes, and the excellent images that I get to see here on CN and elsewhere, be they images that result from loads of data taking, followed buy a ton of image processing, or images that result from EAA integration and no post-processing.

 

I was hoping that NV might be able to bring me there visually, but what I am seeing here indicates that the old adage "aperture matters" still holds.  The videos pointed to as examples of what you may see visually are interesting.  They are not really the "wow my pants off" images that I was hyping myself up for.  I certainly appreciate seeing what the scintillation is likely to be, but the big disappointment for me was that the scopes used seem to all be much larger than mine.  I have a TV-85, a Questar 3.5, and a Celestron C6.  f/7, f14.4, and f/10 respectively.  It seems by the example videos that you better have an 11, 14, or 16 inch aperture to be able to see things like these examples show.

 

It's starting to look like I should not be spending $4000-$5000 on NV equipment and filters that ultimately will not give me the real time visual examples that were shown.

 

If I'm going overboard the wrong way, please let me know.

 

Thanks very much for any advice - even if it's advice that I should not be going here.

 

smp

What sort of skies will you be observing under? As you may know I have a tv85 and under dark skies in afocal mode with a 55mm plossl I love the views of larger DSOs such as the North America, California, heart and soul, the veil etc. So you don’t need aperture for great nv views, it’s more about which objects you are wanting to observe imo.



#18 spereira

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Posted 24 August 2019 - 04:08 PM

What sort of skies will you be observing under? As you may know I have a tv85 and under dark skies in afocal mode with a 55mm plossl I love the views of larger DSOs such as the North America, California, heart and soul, the veil etc. So you don’t need aperture for great nv views, it’s more about which objects you are wanting to observe imo.

Just west of Manchester, NH is classified as Bortle 6, I believe.  I cannot see the Milky Way from my driveway where I normally observe.  And, for me, the effort to pack things up and go to a dark site is pretty much a motivation killer, sorry to say.

 

I've been leaning towards purchasing a Mod 3B/C with a C-mount, white phosphor, and manual gain, but I've been looking at the bundle offered by Tele Vue for pretty much the same price, and I'm wondering about going that way with my TV-85.

 

How can I get a good handle on what I'll be able to see?

 

TIA!

 

smp



#19 ngc7319_20

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Posted 24 August 2019 - 04:12 PM

 

For someone that already has and 8" scope and does not want to buy and manage a 16" telescope, then NV does indeed give a very meaningful increase in deep sky performance under dark skies. 

 

 

I guess that is a key point -- that NV lets you see stuff with a 6" or 8" under dark skies that might otherwise require a larger Dob.  Of course my next question would be "OK so how much could I see with NV through a 24" Dob?"  But these videos don't really answer that one.

 

The video of the Mewlon 250 and M27 was rather striking -- I feel I could see more in my 12" Dob that was in that NV video.  But maybe that wasn't really fair?  Not sure what their light pollution situation was.  Also not so much H-alpha in M27.

https://www.youtube....h?v=I7Paem8OSWI

 

Yes I can understand that for emission nebula where the eye has essentially zero sensitivity to H-alpha, that there could be a large gain, depending on the nebula and how much H-alpha emission there is.  There I might expect a huge gain from NV.

 

I guess some of these vendors have a rental program.  Maybe that is the way to go -- try it out first

https://www.ultimate...tals-s/1820.htm


Edited by ngc7319_20, 24 August 2019 - 04:18 PM.


#20 bobhen

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Posted 24 August 2019 - 04:17 PM

So would you say that "cuts through light pollution" is a major reason to do NV?  You say "I see these 'easily' in 'extreme' light pollution near Philadelphia PA"...   I guess seeing faint nebula from a light-polluted backyard could be a good motivation.

 

But if you have dark skies already -- what is your sense about that situation?

Good question.

 

With an intensifier, on any clear night, I can see the Horse Head nebula and sections of Barnard’s loop from the Philadelphia suburbs with a 102mm F5 refractor.

 

If you can you see the Horsehead Nebula and Barnard’s loop from your location with a 4” refractor then lucky you!

 

But as others have said…

 

NV will still make seeing just about any object easier and with more definition with any size telescope.

 

After all, an image intensifier does just that; it intensifies the light gathered by your telescope: photons enter, are converted to electrons, those electrons are increased “many fold”, the increased electrons strike a phosphor screen and are converted back to photons to be observed in an eyepiece by the observer.

 

This means that more photons are delivered to your eye then actually entered the telescope.
So no matter what size scope you use, NV is like getting the light gathering advantage of a larger mirror. BUT ITS EVEN BETTER: with an intensifier you can use really strong filtration (the same filters that imagers use) to "dramatically" increase contrast.

 

And as any observer knows, when it comes to deep sky observing, more light and more contrast is a killer combination.

 

Bob


Edited by bobhen, 24 August 2019 - 04:19 PM.

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#21 bobhen

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Posted 24 August 2019 - 04:31 PM

Just west of Manchester, NH is classified as Bortle 6, I believe.  I cannot see the Milky Way from my driveway where I normally observe.  And, for me, the effort to pack things up and go to a dark site is pretty much a motivation killer, sorry to say.

 

I've been leaning towards purchasing a Mod 3B/C with a C-mount, white phosphor, and manual gain, but I've been looking at the bundle offered by Tele Vue for pretty much the same price, and I'm wondering about going that way with my TV-85.

 

How can I get a good handle on what I'll be able to see?

 

TIA!

 

smp

With an 85mm telescope with 600mm FL you will be able to see the Horse Head Nebula from your backyard on just about any clear night. As a rough guide, any nebulas that are brighter will also be visible: Califonia, N American, Heart and Soul, all THREE sections of the Veil nebula and many more.

 

The TV 85 has a 600mm FL so for small objects like gobulars, small galaxies, etc. you will want to increase image scale. For small objects like globulars etc, your 6” SCT with a 1,500mm FL would be the scope of choice. For example, with NV, golulars show more stars and each takes on a somewhat unique personality.

 

Bob



#22 Gavster

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Posted 24 August 2019 - 04:34 PM

Just west of Manchester, NH is classified as Bortle 6, I believe.  I cannot see the Milky Way from my driveway where I normally observe.  And, for me, the effort to pack things up and go to a dark site is pretty much a motivation killer, sorry to say.

 

I've been leaning towards purchasing a Mod 3B/C with a C-mount, white phosphor, and manual gain, but I've been looking at the bundle offered by Tele Vue for pretty much the same price, and I'm wondering about going that way with my TV-85.

 

How can I get a good handle on what I'll be able to see?

 

TIA!

 

smp

Clearly the best way is to try before you buy - one of my astronomy club members had an older nv device so this gave me a good indication. The videos and images do give a broad indication of the type of views you could get so are pretty helpful though. Most people once they’ve got an nv device for astronomy are very happy (or more!) with their purchase which possibly also gives some comfort that it would be a worthwhile spend.



#23 ngc7319_20

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Posted 24 August 2019 - 06:38 PM

With an 85mm telescope with 600mm FL you will be able to see the Horse Head Nebula from your backyard on just about any clear night. As a rough guide, any nebulas that are brighter will also be visible: Califonia, N American, Heart and Soul, all THREE sections of the Veil nebula and many more.

 

Horse Head in a TV85 is most impressive!    These objects are all in the H-alpha category -- where almost anything will beat the eye's sensitivity.  Horse Head in a Dob usually means an H-beta filter to supress the background... And is pretty tough even then.  There's a lot more H-alpha than H-beta emission.



#24 ngc7319_20

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Posted 24 August 2019 - 07:03 PM

 

After all, an image intensifier does just that; it intensifies the light gathered by your telescope: photons enter, are converted to electrons, those electrons are increased “many fold”, the increased electrons strike a phosphor screen and are converted back to photons to be observed in an eyepiece by the observer.

 

This means that more photons are delivered to your eye then actually entered the telescope.
So no matter what size scope you use, NV is like getting the light gathering advantage of a larger mirror. BUT ITS EVEN BETTER: with an intensifier you can use really strong filtration (the same filters that imagers use) to "dramatically" increase contrast.

 

And as any observer knows, when it comes to deep sky observing, more light and more contrast is a killer combination.

 

Bob

Theres more to it than "light amplification."  The NV images are indeed brighter (people record them with their iPhones, etc.), but I am not sure there is significantly more information.  The NV system adds shot noise, dark current, scintillation, etc. that weren't there before.  So it's not just 1000x more photons or whatever the number is.

 

The videos in post #5 and #6 are something to think about, at least for me.  I am left feeling like I've had a similar or better views visually with an 8" to 12" plus an OIII filter. Albeit from some dark location.  Certainly to get these views from the city is impressive.  And yes Horse Head in a TV85 is fantastic -- and maybe 5 or 6 other H-alpha objects.

 

I guess what I'd really like to see is the coma galaxy cluster in real-time view in that TV85 + NV or something like that...  Hmmm...

 

This has been interesting!  Thanks!


Edited by ngc7319_20, 24 August 2019 - 07:05 PM.


#25 Jeff Morgan

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Posted 25 August 2019 - 01:39 AM

Horse Head in a TV85 is most impressive!    These objects are all in the H-alpha category -- where almost anything will beat the eye's sensitivity.  Horse Head in a Dob usually means an H-beta filter to supress the background... And is pretty tough even then.  There's a lot more H-alpha than H-beta emission.

Not just emission nebula.

 

Last month a couple of friends and I got together for dinner and a little observing session. It was one day before full moon. Not a great time for observing, but that was when our respective schedules aligned.

 

One of my friends brought an Astro-Physics Stowaway, a 92mm refractor. We tried to find globular cluster M4. During new moon, the view south from my house is dominated by skyglow and measures SQM 19.1. (I have not measured it under full moon conditions, your guess is as good as mine.)

 

Digital setting circles say we were exactly on target. In a 28mm eyepiece, two (2) stars were visible. Putting in my 27mm NV eyepiece, I attempted to count the cluster members working from West to East. Before reaching the center of M4 I lost count at 30. In case you missed it, 92mm aperture.

 

I have been doing this astronomy thing since 1969 (age 8). Nothing has made a bigger difference in what I can see. Not nebula filters. Not "majesty" eyepieces. Not elephant-sized aperture.

 

And given my light pollution conditions, it has absolutely saved the hobby for me. Not only do I see better from my backyard than my Bortle 2 site (which I can only get to once per month), I can access my backyard on a moments notice. With it's Grab-n-Go capability, a 5 or 10 minute NV astronomy session before bedtime is easy.


Edited by Jeff Morgan, 25 August 2019 - 01:39 AM.

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