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Night vision with a 16 inch dob

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#26 ngc7319_20

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Posted 25 August 2019 - 03:10 AM

...

 

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.

Thanks!!!  That is exactly the kind of info I've been hoping to hear...  Which NV device do you have, and was there some afocal eyepiece setup involved?


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#27 guangtou

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Posted 25 August 2019 - 04:27 AM

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. 

I use a 16 inch, f/4.4 dob with my Mod3. Having gain control makes all the difference to me. I always use my Mod3 at less than half gain, and usually with a 12nm Ha filter. When I use the 7nm Ha filter, the gain is set as low as possible. This certainly sacrifices brightness but is still far brighter and well defined than glass.

 

The other reason for low gain settings is I like to go back and forth between binoculars and the telescope. 

 

The attached pic of the trifid was taken afocal with 17 ethos. Stack of 5, 1 second iPhone pics.

 

The Swan was taken with same set up, except I edited out some noise.

 

the Trifid pic is closer to what is directly observed 

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Edited by guangtou, 25 August 2019 - 07:30 AM.


#28 bobhen

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Posted 25 August 2019 - 07:58 AM

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!

First, videos are NOT a good representation of what is seen in the eyepiece. They magnify scintillation and over emphasize the green tint – and by a lot. The still images are a much closer representation.

 

It’s not just the increased brightness it is also (with the addition of strong filters) the huge increase in contrast that makes some of these impossible observations possible.

 

With an intensifier you have so much light that you can throw some away and take advantage of these strong filters.

 

For example: not only will you see the Veil Nebula easily but you will see the faint center section and you will observe the photo-like streamers in the brighter arc – even in small telescopes like a 4” refractor. With my 210mm reflector these streamers look detailed and photographic.

 

You won’t get image scale out of a TV 85 or a 4” refractor etc. they are used for low power, wide field observing, just like with unassisted observing.

 

For galaxies and small objects, image scale is needed, something in the range of 1,500mm to 3,000mm FL depending on the object.

 

I can only give you a few examples: for years I owned a 15” reflector and never saw galaxy 891 (or the Horse Head or the Flame Nebula for that matter) from my light polluted location. I have seen 891 with a 120mm refractor and the intensifier – its dim but observable – even including its pencil-line dark lane.

 

Faint globular clusters that are unresolved (and it doesn’t matter how large your telescope is, some globulars will always be unresolved) these become resolved and actually become more unique individuals in appearance because the fainter or invisible stars become visible.

 

I was out last night for about an hour and a half with my 4” F5 refractor working at F3.5 and the intensifier
There was a touch of moisture in the sky.

The location was about 8-10 miles outside of Philadelphia in absolutely horrendous light pollution with neighbor’s lights on and a few passing cars. The only place worse to observe would be in the center of Philadelphia itself!

Here is my list of objects observed...

 

M8
IC-4678
Detached nebula: N6559, IC-1274, and IC-4681
The faint connecting bridge from M20 to M8 was also seen.
M20
M17
M16
Sh2-53
M27
Sh-2-88
6888 Crescent Nebula
SH2-101
North American Nebula
Y Sadr Complex: IC-1311, IC-1318, 6914, IC-4996, IC-5068, SH2-112, and more
SH2-115
M22
M28
6642
M7
M6
M11
Cocoon Nebula
Veil Nebula
Lots of Dark Nebula Near the Galactic Center:

 

The big 4 summer nebula were near photographic (and in some ways better) in appearance, resembling 5 to 10-second short exposure images

 

The dark nebulas superimposed over the bright galactic center were easy, hard-edged and very impressive. These dark nebula superimposed over the bright, rich, star-filled galactic core were so impressive that I mumbled out an audible “wow” at the eyepiece.

 

Cygnus was so thick with nebula that the nebulas resembled faint clouds.

 

Seeing a patch of nebula near M27 that most observers don’t even know exists also gives some idea of what can be seen.

 

Again, from near Philadelphia (so no travel), from my front yard, with a 4-inch refractor on a simple alt/az mount. I didn’t even bring out a chair.

 

Bob


Edited by bobhen, 25 August 2019 - 08:01 AM.

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#29 Jeff Morgan

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Posted 25 August 2019 - 12:01 PM

Thanks!!!  That is exactly the kind of info I've been hoping to hear...  Which NV device do you have, and was there some afocal eyepiece setup involved?

 

I'm using the AB NIghtvision Mod 3C. It is capable of prime focus operation and has a manual gain control.

 

That particular observation was at prime focus. In that mode of operation, the Mod 3 is effectively a 27mm eyepiece.


Edited by Jeff Morgan, 25 August 2019 - 12:02 PM.


#30 Rickster

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Posted 25 August 2019 - 04:42 PM

As someone who has both used NV with a 16" dob, and done camera based EAA. I have the following observations to offer.

 

I don't find it hard to believe that the OP's real time dark sky visual NV image is roughly the same as the posted phone images.  See my 2017 notes here.  https://www.cloudyni...s/#entry8067174

 

Regarding Eddgie's advice to Dave.  I think the insight is accurate and well placed.  Considering the image quality that Dave is capable of getting with stacked camera exposures, NV in his scope (as opposed to a 16" dob) isn't even going to be close.  As I have said many times before, the edge that NV has over cameras is that with NV you feel as though you could reach out and touch the nebula (as opposed to reaching out and touching a monitor that has an image of a nebula.)  You cannot get that feeling with a camera.  On the other hand, stacked camera exposures gather orders of magnitude more data than a real time NV visual image.  There is no way that NV can give the same image quality as a camera.  NV and camera based EAA are two very different animals, like dogs and cats.  Some people only like dogs, others only like cats and others like both.  I happen to like dogs and cats, and I happen to like cameras and NV.  So I think the advice, and Dave's reaction to the advice is good.  If you are used to one form of EAA and are thinking about also doing the other kind, try it out first.  You may or may not like it.



#31 Jeff Morgan

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Posted 26 August 2019 - 12:06 PM

As someone who has both used NV with a 16" dob, and done camera based EAA. I have the following observations to offer.

 

I don't find it hard to believe that the OP's real time dark sky visual NV image is roughly the same as the posted phone images.  See my 2017 notes here.  https://www.cloudyni...s/#entry8067174

 

Regarding Eddgie's advice to Dave.  I think the insight is accurate and well placed.  Considering the image quality that Dave is capable of getting with stacked camera exposures, NV in his scope (as opposed to a 16" dob) isn't even going to be close.  As I have said many times before, the edge that NV has over cameras is that with NV you feel as though you could reach out and touch the nebula (as opposed to reaching out and touching a monitor that has an image of a nebula.)  You cannot get that feeling with a camera.  On the other hand, stacked camera exposures gather orders of magnitude more data than a real time NV visual image.  There is no way that NV can give the same image quality as a camera.  NV and camera based EAA are two very different animals, like dogs and cats.  Some people only like dogs, others only like cats and others like both.  I happen to like dogs and cats, and I happen to like cameras and NV.  So I think the advice, and Dave's reaction to the advice is good.  If you are used to one form of EAA and are thinking about also doing the other kind, try it out first.  You may or may not like it.

 

Dogs and cats? Not that close I think!

 

The cell phone imaging is fun, but as you say the quality ...

 

I tried to do some post-processing with my cell phone images. Wasted time.

 

Of course, since my images have so much room for improvement, I will still do the cell phone stuff. But it has left me wanting to try "real" imaging. Equipment acquisition has already begun.

 

It's a slippery slope.


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#32 Rickster

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Posted 26 August 2019 - 01:16 PM

Dogs and cats? Not that close I think!

 

The cell phone imaging is fun, but as you say the quality ...

 

I tried to do some post-processing with my cell phone images. Wasted time.

 

Of course, since my images have so much room for improvement, I will still do the cell phone stuff. But it has left me wanting to try "real" imaging. Equipment acquisition has already begun.

 

It's a slippery slope.

Your Epsilon would be an excellent EAA OTA.  Combine it with a good camera (e.g., 294) and a quality mount and you would have a general purpose rig that would be hard to beat.  Not sure if your weather warrants remote control, but many of us in cooler (and/or buggier) climates favor remote control from the comfort of a warm room.



#33 Jeff Morgan

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Posted 26 August 2019 - 03:45 PM

Your Epsilon would be an excellent EAA OTA.  Combine it with a good camera (e.g., 294) and a quality mount and you would have a general purpose rig that would be hard to beat.  Not sure if your weather warrants remote control, but many of us in cooler (and/or buggier) climates favor remote control from the comfort of a warm room.

Remote control? Comfort? Now you are speaking my language! Presumably you are talking about everything running over wifi. More research required ...

 

The scopes and mounts are already in place: the Epsilon, a Lomo SV 80, and a TMB 130SS. Need a flattener(s) for the refractor(s). May even try some planetary with my 16" f/7 ServoCAT dob (just to tie it back on topic grin.gif ).

 

I picked up a TTS Panther mount with the rOTAtor (TTS name for a tube field de-rotator).

 

Still need most of the rest. I've been lurking on the Beginners forum to see what that entails. It would seem that I need:

 

- Guide scope and camera;

- Imaging Camera;

- Filters for Camera;

- Sacrificial budget Windows laptop (probably easier than installing Windows 10 on my MacBook Pro, and I won't care if the PC gets beat up);

- Plate solver;

- PixInsight;

- Large external drive for image storage;

- Auto focus equipment;

- New desktop computer to run PI (MacBook Pro is only 2 cores, 2.5 ghz); and

- ?

 

Moral of the story? Taking cell phone photos can end up being expensive!



#34 Rickster

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Posted 26 August 2019 - 06:43 PM

It looks like you are gearing up to do AP instead of (or in addition to?) EAA? You don't need PI for EAA.  And autoguiding isn't necessary.  Individual exposures are rarely longer than 30sec, with about 10 exposures stacked in Sharpcap (or, if you are using a DSLR, Astrotoaster/Deep Sky Stacker).  I am set up for autoguiding, but only use it on nights of  exceptional seeing when I want to see how much detail I can get.  It isn't worth the trouble on most nights.

 

There are many ways to solve the remote control riddle.  I use wifi to control the mount via ASCOM, Cartes du Ciel and All Sky Plate Solver.  Point and click at what you want to see on the planetarium sky map and the telescope slews to the target.  Like shooting fish in a barrel.  So easy, almost feel guilty.

 

I have 4 telescopes/cameras co-mounted and download images over USB to a Dell T7500 12 core XEON w/72 GB RAM in my control room (which has two 32" inch TVs and two 19" monitors).  The USB is soon to be Ethernet.  Some use wifi for everything.  That usually involves a remote mini computer located at the mount.  The remote computer does the heavy lifting and the indoor computer remotes to it via wifi/Remote Desktop or Team Viewer.  This reduces the amount of data that must be transferred.  Noah4x4 has probably done the most research in this area. 

 

Oh, and since you will be inside with your beverage of choice and not sitting outside in the dark and cold, you may as well figure on a big 4k TV for a monitor. grin.gif


Edited by Rickster, 26 August 2019 - 06:45 PM.


#35 GeezerGazer

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Posted 27 August 2019 - 04:09 PM

Thanks for posting Gavin.  As always, your images are splendid!  16" of fast aperture does make a difference. 

 

As much as anyone, I appreciate Edggie's cautions about coming to NV from photo or video astronomy.   The true differences between NV used visually and for imaging is significant but difficult to quantify because of the many variables.  Even between similar aperture objectives, there can be very dramatic differences if the focal ratio is substantially different.  To me, the difference between glass eyepieces and NV is easier for comparison, because on most DSOs, there is simply no comparison.

 

There was an example of M27 above, where the glass eyepiece is better than the NV eyepiece image.  That is true in my opinion.  And there are a few other DSO's where it is also true... totally dependent on their emission lines.  But on the vast majority of DSO subjects, the NV image is far superior to glass.  I don't mind using a glass eyepiece once in a while to view the few DSO's that look best through glass.  But I can clearly quantify how often I actually use glass eyepieces compared to NV as an eyepiece on DSOs.  The answer is less than 1% of the time... 0% of the time during the past 8 months.  Where I use glass eyepieces exclusively for planetary, doubles, colorful stars or open clusters, I use NV almost exclusively for emission nebulae, dark nebulae, globulars and galaxies.  I used to look at M27 often with glass eyepieces because it actually looks good through a glass eyepiece.  But there are many, many emission nebulae that are a lot more fun to observe with NV.  

 

When I started with NV, my hope was to use it with my f:7 refractor.  I have changed to an f:4 Newt with a good reducer for f:2.8, because the focal ratio does impact NV performance.  I still don't observe from my home though... I much prefer my green zone site, 40 miles away.  The drive works better than any filter I have used to improve on NV... which is also true with my glass eyepieces.  Once in a while I do go outside with the NV, handheld, at 1x, 2x or 4x to look at the sky for a while, which is phenomenal.  But my main, telescopic observations and phonetography are done where it is darker... that's just a personal preference, because NV observations can be done from heavily light polluted skies quite successfully, using the right filter for the conditions.  



#36 bobhen

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Posted 27 August 2019 - 06:00 PM

 

 

There was an example of M27 above, where the glass eyepiece is better than the NV eyepiece image.  That is true in my opinion.  And there are a few other DSO's where it is also true... totally dependent on their emission lines.  But on the vast majority of DSO subjects, the NV image is far superior to glass.

 

Actually the best view of M27 I've had was with my Mewlon and the Micro with a .7nm Ha filter.

 

Good image scale and still brighter than my old 15" reflector using glass and visual filters. The detail compared well to a 5 to 10 second video image with my old  C-11.

 

Here is a quote from my log...

 

M27: "Photo-like" detail: Bright core section: thin edge outline: ears. The amount of detail was like a 5 to 10 second video image. This was a surprise and a "killer view" in the Mewlon working at F8.

 

Bob




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