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Help me understand NV gear.

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#1 gezak22

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Posted 16 April 2017 - 03:27 PM

Hey all,

 

I am intrigued by night vision equipment for visual astronomy. I read through this and this but things are still a bit hazy.

 

Suppose I were to buy a Mod3 Modular Monocular for my TV101, does the Mod3 attach directly to any eyepiece I own? Or is it attached to my head the entire time? If I have some wide field naglers, will the Mod3 catch the entire field of view? Or does the Mod3 replace eyepieces altogether? And what is the AFOV of the Mod3?

 

Also, what gear would I need to give me the most 'bang for the buck' NV experience with my 4" f/5 Apo, and what can I reasonably expect to see with that gear from mag 6.5+ skies?

 

Thanks.

 

Edit: Could I use NV gear on my 11" f/7 Celestron Edge?



#2 Jeff Morgan

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Posted 16 April 2017 - 04:36 PM

It's so easy ... The Mod 3 can be used many ways, but to keep this simple I will describe just one - using it as a telescope eyepiece:

 

The Mod3 has it's own objective lens. Think of it as a mini telescope. Objective lens -> Body -> Eyepiece.

 

The Mod3 objective lens is attached to the NV device using what is called a C-mount thread. It's a pretty standard thing in the photographic world.

 

1) You go to ScopeStuff and by a C-Mount adapter in either 1-1/4" or 2" size (your choice);

2) Thread the objective lens off of the NV body;

3) Thread the C-mount adapter on to the NV body; and

4) Insert in telescope focuser.

 

Congratulations. You have just turbo-charged your telescope!

 

The device functions just like an eyepiece. The approximate focal length is 26mm, and AFOV is 40 degrees.

 

And Yes, you can use the Mod 3 with your Celestron - or any other telescope that takes a standard eyepiece.

 

As to what you can expect to see - the short answer is lots of nebula you'll never see conventionally!


Edited by Jeff Morgan, 16 April 2017 - 04:36 PM.


#3 gezak22

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Posted 16 April 2017 - 04:42 PM

It's so easy ... The Mod 3 can be used many ways, but to keep this simple I will describe just one - using it as a telescope eyepiece:

 

The Mod3 has it's own objective lens. Think of it as a mini telescope. Objective lens -> Body -> Eyepiece.

 

The Mod3 objective lens is attached to the NV device using what is called a C-mount thread. It's a pretty standard thing in the photographic world.

 

1) You go to ScopeStuff and by a C-Mount adapter in either 1-1/4" or 2" size (your choice);

2) Thread the objective lens off of the NV body;

3) Thread the C-mount adapter on to the NV body; and

4) Insert in telescope focuser.

 

Congratulations. You have just turbo-charged your telescope!

 

The device functions just like an eyepiece. The approximate focal length is 26mm, and AFOV is 40 degrees.

 

And Yes, you can use the Mod 3 with your Celestron - or any other telescope that takes a standard eyepiece.

 

As to what you can expect to see - the short answer is lots of nebula you'll never see conventionally!

Thanks!

 

40 degrees? What a bummer. There are no options to go to 60 degrees?



#4 Eddgie

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Posted 16 April 2017 - 05:27 PM

In practice, the field is so full of stars and nebula that you never even think about the apparent field of view.

 

A giant apparent field of nothing to see is a giant empty field.   A 40 degree apparent field full of stars and nebula is breathtaking. 



#5 gezak22

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Posted 16 April 2017 - 05:42 PM

In practice, the field is so full of stars and nebula that you never even think about the apparent field of view.

 

A giant apparent field of nothing to see is a giant empty field.   A 40 degree apparent field full of stars and nebula is breathtaking. 

Would this one be considered to be the state of the art of what this field has to offer? The difference between white and green phosphor is entire limited to the color, not the brightness of the image, right? It will fit right into my 1.25" or 2" diagonal without issues and it will come to focus right out of the box?

 

I understand that H-alpha filters are a must have for nebulae. Would a UHC filter work too or would it result in a major hit in image contrast?



#6 Jeff Morgan

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Posted 16 April 2017 - 05:52 PM

 

In practice, the field is so full of stars and nebula that you never even think about the apparent field of view.

 

A giant apparent field of nothing to see is a giant empty field.   A 40 degree apparent field full of stars and nebula is breathtaking. 

Would this one be considered to be the state of the art of what this field has to offer? The difference between white and green phosphor is entire limited to the color, not the brightness of the image, right? It will fit right into my 1.25" or 2" diagonal without issues and it will come to focus right out of the box?

 

I understand that H-alpha filters are a must have for nebulae. Would a UHC filter work too or would it result in a major hit in image contrast?

 

That's it!

 

As far as focusing, it takes very slightly more inward focus than a 31 Nagler. Nothing extraordinary.

 

Green vs. White phosphor is mostly a preference thing. Supposedly, white is less fatiguing in longer sessions and the military is going white for that reason. Interestingly, when I bought mine the green tubes had slightly higher specs. Could have been a luck of the draw thing though.

 

The white tubes have a slightly bluish cast to my eyes. You forget about it almost immediately. The users of green tubes say the same thing!

 

You will want a minimum of two filters: A long-pass filter for general viewing (something like 640nm, or possibly 610 if you have very dark skies already), and a H-Alpha for nebula. The 12nm H-a is a good first choice.

 

I have not tried standard nebular filters, the trailblazers in the NV field have reported disappointing results with them. But if you already own them, why not try them?



#7 gezak22

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Posted 16 April 2017 - 06:25 PM

Alright, that's fairly straightforward then.

 

What is the purpose of the long pass filter? Just to cut out light pollution?

 

Export limits: Can I take it to the southern hemisphere for astronomy as long as I don't sell it?



#8 Rickster

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Posted 16 April 2017 - 08:05 PM

 

It's so easy ... The Mod 3 can be used many ways, but to keep this simple I will describe just one - using it as a telescope eyepiece:

 

The Mod3 has it's own objective lens. Think of it as a mini telescope. Objective lens -> Body -> Eyepiece.

 

The Mod3 objective lens is attached to the NV device using what is called a C-mount thread. It's a pretty standard thing in the photographic world.

 

1) You go to ScopeStuff and by a C-Mount adapter in either 1-1/4" or 2" size (your choice);

2) Thread the objective lens off of the NV body;

3) Thread the C-mount adapter on to the NV body; and

4) Insert in telescope focuser.

 

Congratulations. You have just turbo-charged your telescope!

 

The device functions just like an eyepiece. The approximate focal length is 26mm, and AFOV is 40 degrees.

 

And Yes, you can use the Mod 3 with your Celestron - or any other telescope that takes a standard eyepiece.

 

As to what you can expect to see - the short answer is lots of nebula you'll never see conventionally!

Thanks!

 

40 degrees? What a bummer. There are no options to go to 60 degrees?

 

In NV, the sensor is directly exposed to the image projected by the objective lens.  The formulas used for calculating field of view are the same as those used for a camera.  The true field of view is determined by the focal length of the objective and the sensor size (18mm diameter in this case).  Since the sensor size is fixed, focal length is the only factor that can be used to change FOV.  If you want wider FOV with NV, you use an objective with a shorter focal length (or use a focal reducer).  As it turns out, an 18mm sensor provides the same true FOV as a 26mm fl / 40 degree apparent FOV eyepiece (or a  15mm fl / 70 degree apparent FOV eyepiece.  This website can be used to do the math.  https://astronomy.to.../field_of_view/

 

OK, that is the math.  But the "feeling" is something different.  To me, a PVS-7 gives a feeling of immersion that is far better than a 70 degree AFOV eyepiece.  I haven't looked through a mod 3, so I can't speak to it.

 

Your 500mm f5 APO will work great with NV.  It will give enough FOV for nearly all of the large nebula.  If you want to go wider, add a focal reducer.  Even wider, use a 100mm or 200mm lens. Bottom line...You wont miss your ultra wideview eyepieces.



#9 gezak22

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Posted 16 April 2017 - 09:46 PM

I don't care about the TFOV as much as I do about AFOV. But since that is fixed, I'll stop worrying about it.

 

Will my 4" f/5 Apo show me the elephant's trunk nebula? Will I be able to see the dark lanes in the Rosette nebula?



#10 pwang99

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Posted 17 April 2017 - 12:45 AM

The elephant trunk nebula is readily visible at 1x and 3x, and of course in your scope as well if it is wide enough.  It is unmistakable and I actually "discovered" it on one of my first outings with my PVS-7s last year, because it's hanging out right next to the Deneb complex of nebulosity.  I remember thinking, "Hmm, is that a cloud floating there?" before realizing it was the Garnet Star nebula. 

 

Now, whether or not you will see the Elephant Trunk within the nebulosity is a somewhat different question.  I have not been able to see it with my C11 reduced by 0.5x, but I wasn't trying very hard either, and it wasn't under great conditions.  This summer, I will be trying a lot harder for dark nebula and surveying a range of those with my APO and with my C11.

 

I can say that I've been able to directly visually observe the Cone Nebula with my C11 at f/5, and that was faint but unmistakable.

 

The Rosette in your APO is going to be marvelous.  I have a 130mm / 1000m FL APO, and when reduced down to 500mm FL, it showed the Rosette beautifully.  I gazed at the petals for what must have been 10 minutes, despite being really cold and tired at the end of my observing session.  Here is a really underwhelming hand-held phone camera shot, giving you a noisy flavor of what you will see... As with all phone shots of NV, your experience at the eyepiece will be far, far, far better.

 

Rosette
 
Since you seem to be interested in dark nebula, I thought I'd also attach a photo of what the Flame and Horsehead look like, in the same scope setup.  The dark lanes in the Flame are quite distinct.  The horsehead is unmistakable but in a 130mm objective, it's hard to make out too much structure.  I have reports that in a 20" dob, you can observe quite a bit of structure in the mane of the "horse head" itself.
 
Flame and Horsehead


#11 Jeff Morgan

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Posted 17 April 2017 - 01:14 AM

What is the purpose of the long pass filter? Just to cut out light pollution?

 

Export limits: Can I take it to the southern hemisphere for astronomy as long as I don't sell it?

 

The long pass filter cuts out any wavelength shorter than it's passband. Basically, they are deep red filters. How strong you use depends upon ambient light pollution. Most light pollution is designed to help people see at night, so it concentrates (is worst) in the shorter visual wavelengths. By happy coincidence, NV tubes are most sensitive in red and near infrared wavelengths.

 

There are several sources, so the exact cut-offs may vary a bit. Generally, the choices are around 610, 640, and 680. For minimal light pollution 610, for heavy light pollution 680.

 

Regarding taking a NV tube out of the country - get professional/legal advice. US made devices are subject to heavy controls.



#12 pwang99

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Posted 17 April 2017 - 01:55 AM

I second Jeff's recommendation to get solid professional advice, perhaps from the vendor you buy the NV gear from.

 

I don't know if TSA has a list of common ITAR items to keep and eye out for, but if so, I'd imagine that night vision gear is pretty high up on that list.



#13 Eddgie

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Posted 17 April 2017 - 08:18 AM

Technically, there is an approval process for international travel with NV gear (not export) but it took 6 months for me to even hear from the authority that handles this kind of request and the reply to my inquiry was sparse and lacked anything approaching detailed instructions on how to proceed. 



#14 cnoct

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Posted 17 April 2017 - 09:44 AM

40 degrees? What a bummer. There are no options to go to 60 degrees?


It isn't so much the 40˚ at unity that's a bummer, well for meteor showers it can be.

The real killjoy can be the fixed focal length of these systems when used in place of a traditional eyepiece i.e. prime configuration.

However there are ways to increase image scale, using a barlow, powermate or in an afocal configuration i.e. behind a traditional eyepiece.

All these options are going reduce system gain by a fair margin but depending on the target, the increased image scale can be worth the hit in system gain.

 

Having started out in NV astronomy with a system that could only be used with a telescope in an afocal configuration, I'd say it's the most versatile means by which to increase image scale. Though if your doing aggressive filtering such as is used for H-a rich targets, go with powermate or barlow. The loss through the afocal configuration is often to great.

With any of the current NV astronomy systems e.g. MOD-3c,  NVD Micro and PVS-7's, your not limited to any one configurations so the killjoy of the focal length can be mitigated to a great degree.


Edited by cnoct, 17 April 2017 - 11:15 AM.


#15 gezak22

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Posted 17 April 2017 - 11:34 AM

I think I get the idea. What this subforum really needs is a graphical illustration of what can be reasonably expected. I'm not new to the hobby, so noisy/pixelated images get the idea across, but we could capture a lot more newbies if we had comparison sketches showing what a 4" telescope produces with and without NV, same deal for a larger scope.

 

I'll play with my software to see how many suitable targets ... whom am I kidding. I'll cave like I always do, buy it, and experiment with the real deal. If I don't like it, I'll sell. You are all a terrible influence ... and I love you all because of it. :)



#16 Jeff Morgan

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Posted 17 April 2017 - 11:59 AM

I think I get the idea. What this subforum really needs is a graphical illustration of what can be reasonably expected. I'm not new to the hobby, so noisy/pixelated images get the idea across, but we could capture a lot more newbies if we had comparison sketches showing what a 4" telescope produces with and without NV, same deal for a larger scope.

 

I'll play with my software to see how many suitable targets ... whom am I kidding. I'll cave like I always do, buy it, and experiment with the real deal. If I don't like it, I'll sell. You are all a terrible influence ... and I love you all because of it. smile.gif

 

Sketch?! Sorry, I can only do stick people.

 

Best approximation I have seen (photographic) are by jdbastro:

 

https://www.cloudyni...ied-astro-pics/



#17 bobhen

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Posted 17 April 2017 - 02:06 PM

 

I think I get the idea. What this subforum really needs is a graphical illustration of what can be reasonably expected. I'm not new to the hobby, so noisy/pixelated images get the idea across, but we could capture a lot more newbies if we had comparison sketches showing what a 4" telescope produces with and without NV, same deal for a larger scope.

 

I'll play with my software to see how many suitable targets ... whom am I kidding. I'll cave like I always do, buy it, and experiment with the real deal. If I don't like it, I'll sell. You are all a terrible influence ... and I love you all because of it. smile.gif

 

Sketch?! Sorry, I can only do stick people.

 

Best approximation I have seen (photographic) are by jdbastro:

 

https://www.cloudyni...ied-astro-pics/

 

If, for example, you take the Rosette and the last Horsehead Nebula image (near the bottom) from the images in the link above and dim them down 50-60%, that is about what I see in real time using my NVD Micro, a .7nm Ha filter, and my Tak 120 refractor.

 

And I can see them from a gray zone in the Philadelphia, PA suburbs in horrendous light pollution where the Horsehead Nebula is never visible using regular eyepieces in any size telescope let alone a "small" 120mm refractor.

 

The Horsehead Nebula is a "routine" object now!

 

Bob


Edited by bobhen, 17 April 2017 - 02:07 PM.


#18 Jeff Morgan

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Posted 17 April 2017 - 03:38 PM

If, for example, you take the Rosette and the last Horsehead Nebula image (near the bottom) from the images in the link above and dim them down 50-60%, that is about what I see in real time using my NVD Micro, a .7nm Ha filter, and my Tak 120 refractor.

 

And I can see them from a gray zone in the Philadelphia, PA suburbs in horrendous light pollution where the Horsehead Nebula is never visible using regular eyepieces in any size telescope let alone a "small" 120mm refractor.

 

The Horsehead Nebula is a "routine" object now!

 

Bob

 

 

Keep in mind that on nebula, focal ratio of the host telescope will be a factor.

 

So true on the HorseHead! I wonder if I will ever get tired of it?

 

To give Geza an idea of what NV can do - I have caught the HorseHead with a Meade ETX90 f/13.8 Maksutov using a H-alpha 12nm filter. Direct vision.

 

Not as pretty as it is in the f/3.7 Comet Catcher, but that it can be seen with a 90mm aperture by itself speaks volumes as to the reach of NV.



#19 Eddgie

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Posted 18 April 2017 - 08:00 AM

I think I get the idea. What this subforum really needs is a graphical illustration of what can be reasonably expected. I'm not new to the hobby, so noisy/pixelated images get the idea across, but we could capture a lot more newbies if we had comparison sketches showing what a 4" telescope produces with and without NV, same deal for a larger scope.

 

I'll play with my software to see how many suitable targets ... whom am I kidding. I'll cave like I always do, buy it, and experiment with the real deal. If I don't like it, I'll sell. You are all a terrible influence ... and I love you all because of it. smile.gif

Cnoct (Carpe Nocturnum on YT) and JDBAstro (JDB_Astro on YT) have tons of real time videos on Youtube that show what you can see and they are not approximations.  They are real time views and while the camera does not always show the view as well as seeing it directly in the eyepiece, it gives a far better rendition of what can be seen than most people could sketch. 



#20 gezak22

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Posted 24 April 2017 - 11:24 PM

Alright, I pulled the trigger on a c-mounted Mod3 along with a 1.25" 5nm Halpha filter.

 

Any tips on how to not destroy it? Can I point it unfiltered at the moon with my 4" refractor without causing damage?



#21 Starman81

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Posted 25 April 2017 - 12:30 AM

Alright, I pulled the trigger on a c-mounted Mod3 along with a 1.25" 5nm Halpha filter.

 

Any tips on how to not destroy it? Can I point it unfiltered at the moon with my 4" refractor without causing damage?

 

Not exactly sure why you would want to do that for no benefit at all and risk a very expensive piece of equipment. :shrug:



#22 Vondragonnoggin

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Posted 25 April 2017 - 03:57 AM

PVS-4 gen 3 tube approx 65° AFOV (25mm tube, not an 18mm tube)

 

yes, sketching done - M42 in 152mm refractor, .5x reducer, gen 3 night vision with 7nm Ha filter:

 

732DAC3D-3B31-48A4-BCF4-1E9CA13CB6C5_zps



#23 Vondragonnoggin

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Posted 25 April 2017 - 04:02 AM

Sketch done in an ipad app. Border white/red zone light pollution. No tracking, manual mount. First sketched on paper and transferred to app for better representation of the real view.

 

I did not sketch in the scintillation. Haha. I submitted this a couple years ago in sketching forum.

 

25mm tube devices are huge compared to the 18mm tube devices. Not for everyone, nor for the faint of heart with delicately balanced scopes only taking light eyepieces. My pvs-4 is approx the weight of a 31mm Televue Nagler with the single lens biocular on it and only slightly lighter with standard monocular eyepiece on it, but it does go to about 65° AFOV or so.

 

Gen 3 25mm tubes are getting harder to find.


Edited by Vondragonnoggin, 25 April 2017 - 04:09 AM.


#24 Eddgie

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Posted 25 April 2017 - 08:17 AM

A beautiful sketch.

 

I can't get that much extension on Orion from where I live, but I get more than I used to get from the darkest skies I ever took conventional equipment to.    

 

And the structure I can see in Orion is photographic.  Ever from my home just outside of a white zone, Orion has such richness in the detail that many astro-pics simple can't do it justice.   Most don't show the dynamic range of brightness the way the live view looks in the real time view of the image intensifier.

 

Now Orion is very bright so not all Nebula will do as well, but I see way more structure in all nebula than I have ever seen prior and I seen Nebula that I never even knew existed!

 

I have checked off more bucket list items using NV in the last two years than I have in the previous 40 years put together.   And I didn't just "see" them as bare suggestions of what they are, but I could see richness in them.

 

I have seen more galaxies than I ever thought possible from my home, but as compared to nebula, most galaxies are dull. There are nebula out there that are so rich and complex that you can view them over and over and over and always find new detail to see in them. 


Edited by Eddgie, 25 April 2017 - 08:18 AM.


#25 Jeff Morgan

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Posted 25 April 2017 - 10:05 AM

Sketch done in an ipad app. Border white/red zone light pollution. No tracking, manual mount. First sketched on paper and transferred to app for better representation of the real view.

 

Amazing sketch!

 

Particularly in light of where it was made, so to speak.




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