Jump to content

  •  

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

Photo

NV - does it look more like a screen or eyepiece

  • Please log in to reply
80 replies to this topic

#1 joelin

joelin

    Vanguard

  • *****
  • topic starter
  • Posts: 2,143
  • Joined: 14 Jan 2008
  • Loc: Saratoga, CA

Posted 02 December 2019 - 02:39 PM

I don't have any NV devices and never looked through one before so I'm wondering what the experience of looking through one is:

 

1) what is the resoltuion? Is it more like looking at the back of my DSLR where I can easily see the pixelation or a high quality eyepiece at a dark site?

2) how wide is the apparent field of view? Is a narrow eyepiece around 50 degrees, a wide one like 70 degrees or ultra wide like 100 degrees?

3) what is the contrast? do dim stars and brighter stars have a similar appearance as they would in a photograph versus visually where the dim stars are almost not there and require averted vision 

 



#2 pkrallis

pkrallis

    Mariner 2

  • *****
  • Posts: 224
  • Joined: 06 Oct 2007
  • Loc: Colorado Springs, CO

Posted 02 December 2019 - 03:11 PM

Haven't looked through any since 1968 but it never occurred to me to look at stars with them back then.  I hope they have improved as I recall everything was a bit greenish.smile.gif 



#3 Dale Eason

Dale Eason

    Apollo

  • *****
  • Posts: 1,356
  • Joined: 24 Nov 2009
  • Loc: Roseville,Mn.

Posted 02 December 2019 - 03:13 PM

Mine Mod3C is much like an eyepiece view.  The apparent field of view is 40 deg but the widest 40 deg you have ever seen when hand held at 1-3x.  The field of view for hand held is bigger than most binos I have looked through.  Much larger than my finders.

 

Dale


  • outofsight likes this

#4 havasman

havasman

    Voyager 1

  • ****-
  • Posts: 10,069
  • Joined: 04 Aug 2013
  • Loc: Dallas, Texas

Posted 02 December 2019 - 03:25 PM

I have an NV device and do not much fancy it. A modern Mod3C high-spec green film unit kitted to run w/ or w/o various filters and w/ or w/o a scope, the presentation is poor. Resolution is poor. It is nothing like an eyepiece at all. It does amplify the light and shows an image of fainter objects than are seen w/o it but that image does not satisfy my expectations.

 

However, it is quite a bit of fun to sit on the 2nd floor deck of friends' lake house in central Texas on a dark overcast night and let their children watch deer and raccoons move across the property and head down to the lake. Viewed just before sunup, the ashes of a campfire that is long "out" glow brightly in the center, showing  that a fire long burned down retains heat for many hours.

 

The FOV depends on how it is set up.

 

Contrast lags far behind an eyepiece view via any of my scopes and is not like a photographic image except for those low-res ones captured via NV device.


Edited by havasman, 02 December 2019 - 03:53 PM.


#5 Jeff Morgan

Jeff Morgan

    Voyager 1

  • *****
  • Posts: 11,249
  • Joined: 28 Sep 2003
  • Loc: Prescott, AZ

Posted 02 December 2019 - 03:33 PM

Assuming you are getting a relatively new device (and not something from the Viet Nam era or the first Desert Storm):

 

Resolution

 

Generally very good to excellent. Bright stars will halo. How much depends upon the halo rating of the tube. But note this is not a measure of resolution - it is the detector being saturated by that star. What you want to look at are the stars of mid-range or fainter. Preferably fainter. These should be pin-point.

 

A month ago there was a thread on the Eyepieces forum where the usual NV haters made the usual claims that NV devices "lack resolution". I decided to do an empirical experiment by printing a standard eye chart, and using my NVD to read it. Results: At the proscribed distance of 10 feet I had no difficulties reading from the 20/20 line.

 

The ability to read the lines was dependent upon illumination - just like normal vision! Not surprising since the final link in that chain was a human eyeball.

 

As far as compared to a conventional eyepiece, if you have manual gain you can make this so by turning down the gain on the intensifier. My device is white phosphor, and I can make it dim enough it is difficult to differentiate from my Meade 26mm Plossl. But why? Makes as much sense as buying a 20" Dob and masking it down to 4".

 

AFOV

 

If you think that AFOV is the primary function and defining performance measure of an eyepiece, you will not like NV. AFOV on most devices is 40 degrees. 

 

Averted Vision and Dynamic Range

 

One can use averted vision with NV. However, why? Just like getting a larger scope, the idea is to make the Faint Bright. Averted Vision is the ultimate in low resolution vision! Your goal in any situation should be to use direct vision so as to realize the full resolution of your eye. Averted vision should be the tool of last resort for the dimmest targets.

 

The other part of your question deals with dynamic range. No device - film, digital, NV - made by man has the dynamic range of the eye. That is a fact of life.

 

But it does open up possibilities. For example, this time of year a popular observing challenge is the HorseHead nebula. I don't know your experience level, but suffice it to say many boxes need to be checked for a chance at success - such as excluding 2nd magnitude Alnitak from the field of view. While your eye has excellent dynamic range, it can't take it all in at the same time. Alnitak will overwhelm the nebula.

 

With a NVD this is not a concern. In fact, the NV astronomer can frame a nice view with the HorseHead, Alnitak, and the Flame Nebula.

 

And we can do it from the city on any clear night with ridiculously small apertures. All direct vision.

 

One final note - Good thing you stopped here first, as opposed to the Eyepiece Forum. There are a number of people there who do not like the technology - which is fine. Unfortunately, they cross the line by posing as "experts" offering their opinion as facts.

 

Should you find these people, please do ask them if they have ever owned a NVD. If not, get the details from them on the (usually) one time they looked through one. How long ago? What objects did you look at? What device was it? What was the focal ratio of the system? What filter was used? Did you adjust the diopter or gain settings?

 


  • AllanDystrup likes this

#6 joelin

joelin

    Vanguard

  • *****
  • topic starter
  • Posts: 2,143
  • Joined: 14 Jan 2008
  • Loc: Saratoga, CA

Posted 02 December 2019 - 04:05 PM

Assuming you are getting a relatively new device (and not something from the Viet Nam era or the first Desert Storm):

 

Resolution

 

Generally very good to excellent. Bright stars will halo. How much depends upon the halo rating of the tube. But note this is not a measure of resolution - it is the detector being saturated by that star. What you want to look at are the stars of mid-range or fainter. Preferably fainter. These should be pin-point.

 

A month ago there was a thread on the Eyepieces forum where the usual NV haters made the usual claims that NV devices "lack resolution". I decided to do an empirical experiment by printing a standard eye chart, and using my NVD to read it. Results: At the proscribed distance of 10 feet I had no difficulties reading from the 20/20 line.

 

The ability to read the lines was dependent upon illumination - just like normal vision! Not surprising since the final link in that chain was a human eyeball.

 

As far as compared to a conventional eyepiece, if you have manual gain you can make this so by turning down the gain on the intensifier. My device is white phosphor, and I can make it dim enough it is difficult to differentiate from my Meade 26mm Plossl. But why? Makes as much sense as buying a 20" Dob and masking it down to 4".

 

AFOV

 

If you think that AFOV is the primary function and defining performance measure of an eyepiece, you will not like NV. AFOV on most devices is 40 degrees. 

 

Averted Vision and Dynamic Range

 

One can use averted vision with NV. However, why? Just like getting a larger scope, the idea is to make the Faint Bright. Averted Vision is the ultimate in low resolution vision! Your goal in any situation should be to use direct vision so as to realize the full resolution of your eye. Averted vision should be the tool of last resort for the dimmest targets.

 

The other part of your question deals with dynamic range. No device - film, digital, NV - made by man has the dynamic range of the eye. That is a fact of life.

 

But it does open up possibilities. For example, this time of year a popular observing challenge is the HorseHead nebula. I don't know your experience level, but suffice it to say many boxes need to be checked for a chance at success - such as excluding 2nd magnitude Alnitak from the field of view. While your eye has excellent dynamic range, it can't take it all in at the same time. Alnitak will overwhelm the nebula.

 

With a NVD this is not a concern. In fact, the NV astronomer can frame a nice view with the HorseHead, Alnitak, and the Flame Nebula.

 

And we can do it from the city on any clear night with ridiculously small apertures. All direct vision.

 

One final note - Good thing you stopped here first, as opposed to the Eyepiece Forum. There are a number of people there who do not like the technology - which is fine. Unfortunately, they cross the line by posing as "experts" offering their opinion as facts.

 

Should you find these people, please do ask them if they have ever owned a NVD. If not, get the details from them on the (usually) one time they looked through one. How long ago? What objects did you look at? What device was it? What was the focal ratio of the system? What filter was used? Did you adjust the diopter or gain settings?

i brought up averted vision because part of what makes visual astronomy interesting is the high contrast that the sky can have from bright to very faint objects... now if NV can dramatically bring out faint objects...thats awesome, but im guessing there might still be even fainter objects that NV has a difficult time seeing ... and for those to show up with averted vision would be nice 

 

think of it this way, for visual... mag 3-4 stars are direct vision and mag 5-6 for me requires averted vision ...... maybe with NV..mag 7 becomes direct, but would mag 10 then become averted?



#7 outofsight

outofsight

    Apollo

  • *****
  • Posts: 1,476
  • Joined: 31 May 2015

Posted 02 December 2019 - 04:29 PM

i brought up averted vision because part of what makes visual astronomy interesting is the high contrast that the sky can have from bright to very faint objects... now if NV can dramatically bring out faint objects...thats awesome, but im guessing there might still be even fainter objects that NV has a difficult time seeing ... and for those to show up with averted vision would be nice 

 

think of it this way, for visual... mag 3-4 stars are direct vision and mag 5-6 for me requires averted vision ...... maybe with NV..mag 7 becomes direct, but would mag 10 then become averted?

In answer to your original question, any decent Gen 3 NV is more like looking through an EP than looking at a screen. Resolution is just fine and most people quickly get over the green, if that's the color you have.

 

And what you've written kind of sums up what NV will do, we've discussed the magnitude increase before but don't think there's an easy way to state it exactly, just like many viewing aspects, but the increase in what you can see is several orders of magnitude.

 

Here's an example, M13, the Hercules Globular Cluster, with my 10" dob, it's not even a smudge looking at it from my light polluted driveway, add NV and it looks like a regular textbook picture of a globular cluster. Good luck with what you're trying to figure out.



#8 Gavster

Gavster

    Viking 1

  • -----
  • Posts: 713
  • Joined: 07 Mar 2014

Posted 02 December 2019 - 05:00 PM

I have an NV device and do not much fancy it. A modern Mod3C high-spec green film unit kitted to run w/ or w/o various filters and w/ or w/o a scope, the presentation is poor. Resolution is poor. It is nothing like an eyepiece at all. It does amplify the light and shows an image of fainter objects than are seen w/o it but that image does not satisfy my expectations.

 

However, it is quite a bit of fun to sit on the 2nd floor deck of friends' lake house in central Texas on a dark overcast night and let their children watch deer and raccoons move across the property and head down to the lake. Viewed just before sunup, the ashes of a campfire that is long "out" glow brightly in the center, showing  that a fire long burned down retains heat for many hours.

 

The FOV depends on how it is set up.

 

Contrast lags far behind an eyepiece view via any of my scopes and is not like a photographic image except for those low-res ones captured via NV device.

I am a bit surprised that you have been disappointed with your nv system. My experience is that the resolution is excellent and the views much like my glass eyepieces (particularly if I adjust the gain down a little to remove any scintillation). Do you know the actual specs of your tube?


  • Doug Culbertson, outofsight and nimitz69 like this

#9 dr.who

dr.who

    Voyager 1

  • *****
  • Administrators
  • Posts: 14,621
  • Joined: 05 Jan 2012

Posted 02 December 2019 - 05:16 PM

Someone in Cats & Casses just posted in the C14 v. EAA thread that NV is good for nebulae but not for things like galaxies. This seems count intuitive but I have not used Gen 3 (is there now Gen 4?) devices nor did I use the ones I did use for astronomy. Is that a true statement about galaxies and by extension clusters and globs? It doesn’t sound like it but if someone here could answer up authoritatively as well as in the aforementioned thread that would do a lot to either confirm or dispel the statement.

#10 TOMDEY

TOMDEY

    Fly Me to the Moon

  • *****
  • Posts: 5,165
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 02 December 2019 - 05:24 PM

Hi, joelin! Well, I'm certain that if you get it, and use it in "eyepiece" mode on your telescope(s) --- you'll be delighted and hooked for life. Jeff's detailed summary is excellent, and matches my experience. I have three Gen3 and retired the old Collins one, that is too heavy and clunky, compared with the new ones.

 

In addition to the other respondents... another thing that makes NV engaging, comfortable, and "real presence" is that the effective exit pupil is huge, as in gargantuan, nearly an inch across! In the strictest sense, the eyepiece end (that is looking at the phosphor conjugate to infinity) doesn't have a strict exit pupil. It is actually functioning as a 9.8x magnifying glass / eye-loupe, that makes the 18mm phosphor screen subtend 40o. I've never seen that tech aspect discussed here; I actually worked on those optics for ITT. The feeling is that you have superb eye relief. I've even intentionally backed away from the eyepieces (on 16-inch binoscope) by 30mm and still see the whole field sharply. Back away to a whole foot and still see the central 5o sharply. So, the effective eye relief is ~30mm, without vignetting or even kidney bean. And that comfort helps affect the "reality-immersed" experience.

 

Regarding artifactuals of the technology approach. You will see scintillation. This is mostly unavoidable Photon-Arrival Shot Noise. That is, you are actually witnessing the one by one arrival or individual photons (plus some added electron events, that also get amplified). It's not that there is anything wrong with the technology or device... rather, that you are pushing the limit of what mother nature is providing, as photons from the stars and nebulae come rattling down your dinky little telescope tube. That is to say, it doesn't and can't get any better than this. The more expensive grades NV will have better quality control, better contrast, resolution and noise control --- the Gen3s are all pushing the limits of what information is arriving. When we NV fans declare, "It doesn't get any better than this!" --- that is literal --- because it can't get much better than this. [similarity: a broadband back-thinned/illuminated imaging CCD with Quantum Efficiency approaching unity. That's all there is, no more available.]

 

Ummm... Finally, there is the usual learning and getting comfortable with the new lease on observing life. It only takes an hour or so to fall in love with NV, and for your brain to auto-filter out the green colour of the phosphor and entirely ignore (as in not notice) the scintillation. At that gestalt point --- you realize that you are seeing a magnitude or more deeper, and that averted vision is an option, rather than a necessity, and that you are literally seeing into the near infrared, and that the Horsehead is boldly staring you right in the face, up close, and personal!

 

Detractors are either entirely uninitiated, afraid, or just not comfortable with new experiences and rising to the challenge of learning new things. And that probably describes most of us mortals... intimidated by new technologies. Choose to be one of the few who take the plunge and learn how to hang ten... Leave the landlubbers on shore... looking out wistfully, enviously.    Tom  [disclaimer --- Sure, Tom worked for ITT, but he is now just a retired advocate.]

Attached Thumbnails

  • 38 night vision surfing hanging ten.jpg

  • Jim4321 likes this

#11 Gavster

Gavster

    Viking 1

  • -----
  • Posts: 713
  • Joined: 07 Mar 2014

Posted 02 December 2019 - 05:44 PM

Someone in Cats & Casses just posted in the C14 v. EAA thread that NV is good for nebulae but not for things like galaxies. This seems count intuitive but I have not used Gen 3 (is there now Gen 4?) devices nor did I use the ones I did use for astronomy. Is that a true statement about galaxies and by extension clusters and globs? It doesn’t sound like it but if someone here could answer up authoritatively as well as in the aforementioned thread that would do a lot to either confirm or dispel the statement.

Yes that’s broadly correct. Nv is best for emission nebulae since you can use narrowband ha filters which is enhance the views considerably. 
Galaxies are broadband objects so filtering is not as helpful. Nv still works pretty well but because all the light is intensified the jump in views compared to normal glass is not as big (but still lots of fun - I love looking at the whirlpool galaxy, needle galaxy, Leo triplet and bode’s nebula with nv.)

Here is a thread where I show some nv results on galaxies.

https://www.cloudyni...n-and-galaxies/


Edited by Gavster, 02 December 2019 - 06:11 PM.

  • Starman27 likes this

#12 joelin

joelin

    Vanguard

  • *****
  • topic starter
  • Posts: 2,143
  • Joined: 14 Jan 2008
  • Loc: Saratoga, CA

Posted 02 December 2019 - 06:04 PM

Hi, joelin! Well, I'm certain that if you get it, and use it in "eyepiece" mode on your telescope(s) --- you'll be delighted and hooked for life. Jeff's detailed summary is excellent, and matches my experience. I have three Gen3 and retired the old Collins one, that is too heavy and clunky, compared with the new ones.

 

In addition to the other respondents... another thing that makes NV engaging, comfortable, and "real presence" is that the effective exit pupil is huge, as in gargantuan, nearly an inch across! In the strictest sense, the eyepiece end (that is looking at the phosphor conjugate to infinity) doesn't have a strict exit pupil. It is actually functioning as a 9.8x magnifying glass / eye-loupe, that makes the 18mm phosphor screen subtend 40o. I've never seen that tech aspect discussed here; I actually worked on those optics for ITT. The feeling is that you have superb eye relief. I've even intentionally backed away from the eyepieces (on 16-inch binoscope) by 30mm and still see the whole field sharply. Back away to a whole foot and still see the central 5o sharply. So, the effective eye relief is ~30mm, without vignetting or even kidney bean. And that comfort helps affect the "reality-immersed" experience.

 

Regarding artifactuals of the technology approach. You will see scintillation. This is mostly unavoidable Photon-Arrival Shot Noise. That is, you are actually witnessing the one by one arrival or individual photons (plus some added electron events, that also get amplified). It's not that there is anything wrong with the technology or device... rather, that you are pushing the limit of what mother nature is providing, as photons from the stars and nebulae come rattling down your dinky little telescope tube. That is to say, it doesn't and can't get any better than this. The more expensive grades NV will have better quality control, better contrast, resolution and noise control --- the Gen3s are all pushing the limits of what information is arriving. When we NV fans declare, "It doesn't get any better than this!" --- that is literal --- because it can't get much better than this. [similarity: a broadband back-thinned/illuminated imaging CCD with Quantum Efficiency approaching unity. That's all there is, no more available.]

 

Ummm... Finally, there is the usual learning and getting comfortable with the new lease on observing life. It only takes an hour or so to fall in love with NV, and for your brain to auto-filter out the green colour of the phosphor and entirely ignore (as in not notice) the scintillation. At that gestalt point --- you realize that you are seeing a magnitude or more deeper, and that averted vision is an option, rather than a necessity, and that you are literally seeing into the near infrared, and that the Horsehead is boldly staring you right in the face, up close, and personal!

 

Detractors are either entirely uninitiated, afraid, or just not comfortable with new experiences and rising to the challenge of learning new things. And that probably describes most of us mortals... intimidated by new technologies. Choose to be one of the few who take the plunge and learn how to hang ten... Leave the landlubbers on shore... looking out wistfully, enviously.    Tom  [disclaimer --- Sure, Tom worked for ITT, but he is now just a retired advocate.]

when you say seeing a magnitude deeper....are you saying like one magnitude on the scale where its 2.5 times fainter? 

 

if so...that doenst seem like much...



#13 nimitz69

nimitz69

    Surveyor 1

  • *****
  • Posts: 1,649
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 02 December 2019 - 06:12 PM

I have a MOD 3C with WP tube & manual gain and all I can say is with the correct filters the view is nothing short of amazing.  I ALWAYS use it when I have my 14” DOB out and during Club public star parties once the word gets out I have a line at my scope the entire night.  It’s hard to describe how spectacular things like M13 look with a modern Gen 3 NVD with astronomy grade tube .... if you ever get the chance to look through one you’ll understand what all the excitement is about


  • Kevdog and Gavster like this

#14 joelin

joelin

    Vanguard

  • *****
  • topic starter
  • Posts: 2,143
  • Joined: 14 Jan 2008
  • Loc: Saratoga, CA

Posted 02 December 2019 - 07:38 PM

how about frame rates?

 

I have a sony a7s which amplifies light really well with high ISO when in video mode...the downside? its about like 4 FPS.... 



#15 joelin

joelin

    Vanguard

  • *****
  • topic starter
  • Posts: 2,143
  • Joined: 14 Jan 2008
  • Loc: Saratoga, CA

Posted 02 December 2019 - 07:52 PM

some other thoughts, people talk a lot about MOD 3 and that seems to be the best one because it can connect with all your telescopes/camears with an adapter...is this the case?

 

is it better than the one televue released here: http://www.televue.c..._page.asp?id=36  ? this doedsn't seem to allow prime focus photography and you must attach this unit to an eyepiece which doesn't seem too secure to me

 

I'm a bit confused on terminology from here https://tnvc.com/sho...-l-3-omni-viii/ such as

 

L-3 filmed vs unfilmed. what is L-3 and what is film?

gain control...automatic vs manual. i'm thinking manual is better right? so i can dial it to the right setting to minimize noise

lens interface...C mount or standard. i'm thinking i would want C-mount so I can out a 1.25" nosepiece on it right? are there any threaded connections like M42/M48?

 

 and some other terminology:  https://www.modarmor...ular-nv-system/ This has a selection between ITT and Photonis 4G. What is this?


Edited by joelin, 02 December 2019 - 07:52 PM.


#16 bobhen

bobhen

    Gemini

  • *****
  • Posts: 3,447
  • Joined: 25 Jun 2005

Posted 02 December 2019 - 08:03 PM

Someone in Cats & Casses just posted in the C14 v. EAA thread that NV is good for nebulae but not for things like galaxies. This seems count intuitive but I have not used Gen 3 (is there now Gen 4?) devices nor did I use the ones I did use for astronomy. Is that a true statement about galaxies and by extension clusters and globs? It doesn’t sound like it but if someone here could answer up authoritatively as well as in the aforementioned thread that would do a lot to either confirm or dispel the statement.

From my light polluted backyard, I find NV works well on all objects.

 

Just a few non-nebula examples…

When I had my 15” reflector I never even glimpsed galaxy. I can spot it now with a 4” refractor. It’s dim but its there. And with my C11 I the dark lane in galaxy 3628 was maybe glimpsed once or twice in 15-years. My 120mm refractor can now spot that feature easily.

 

With my C11, on a really good night, only a handful of stars were observed in the companion cluster to M35, cluster 2158. With my 120mm refractor the cluster is completely resolved and is killer with M35 in the same filed.

 

Faint globular clusters that are just smudges resolve and have unique shapes and personalities.

 

Of course nebula are outstanding. On any clear night, even from my extremely light polluted location, the Horsehead and Flame Nebulas are visible even in my 4” refractor.

 

Yes, a video camera with a 45-second exposure will show more. But intensifier views are in real-time with all the portability and ease-of-use that real-time observing brings.

 

Without NV, most observers (especially with even mild light pollution) will have missed observing half of what's out there. You will soon have a newfound respect for the Milky Way.

 

Bob



#17 GOLGO13

GOLGO13

    Aurora

  • *****
  • Posts: 4,543
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 02 December 2019 - 08:08 PM

how about frame rates?

I have a sony a7s which amplifies light really well with high ISO when in video mode...the downside? its about like 4 FPS....


It's a real time view in my opinion.

I believe if you were in a really dark sky with an eyepiece, the view is better than night vision in a light polluted sky. But that's the thing. It's like being in a dark sky in light pollution.

So far I have not been able to use it in a dark sky. But it is quite good in light pollution and I understand it gets better in a dark sky.

It has a visual observing feel to it.

And best of all to me is I use it with alt az mounts. I don't have to worry about setting up an eq goto.

And it can be used at 1x and up. Viewing at 1x is really cool. A couple of filters are needed. Hydrogen alpha equal to or below 12nm to 5nm for nebulas. And line pass filters for everything else.

#18 slavicek

slavicek

    Mariner 2

  • *****
  • Posts: 269
  • Joined: 01 Aug 2017
  • Loc: Massachusetts

Posted 02 December 2019 - 09:32 PM

I don't have any NV devices and never looked through one before so I'm wondering what the experience of looking through one is:

 

1) what is the resoltuion? Is it more like looking at the back of my DSLR where I can easily see the pixelation or a high quality eyepiece at a dark site?

 

When you read about the specs at different webs/manufacturers they talk about the resolution being 68-72 lines per millimeter, which is more resolution then the eye can see so the view is "perfect" in this sense. Also the view is instant, no delays, no frame rates. The sintilation sucks but you can manage it using gain control. And of course you have to cough out ~$4500 just to get going. And you want to get the white phosphorus unit!



#19 joelin

joelin

    Vanguard

  • *****
  • topic starter
  • Posts: 2,143
  • Joined: 14 Jan 2008
  • Loc: Saratoga, CA

Posted 02 December 2019 - 09:47 PM

When you read about the specs at different webs/manufacturers they talk about the resolution being 68-72 lines per millimeter, which is more resolution then the eye can see so the view is "perfect" in this sense. Also the view is instant, no delays, no frame rates. The sintilation sucks but you can manage it using gain control. And of course you have to cough out ~$4500 just to get going. And you want to get the white phosphorus unit!

does that mean you can split very close doubles?



#20 joelin

joelin

    Vanguard

  • *****
  • topic starter
  • Posts: 2,143
  • Joined: 14 Jan 2008
  • Loc: Saratoga, CA

Posted 02 December 2019 - 10:25 PM

One more question. Is it possible to attach a camera like a DSLR to the back side of the NV device such as the PVS7 or mod 3? If so, how big is the image circle?

#21 Jeff Morgan

Jeff Morgan

    Voyager 1

  • *****
  • Posts: 11,249
  • Joined: 28 Sep 2003
  • Loc: Prescott, AZ

Posted 02 December 2019 - 10:50 PM

when you say seeing a magnitude deeper....are you saying like one magnitude on the scale where its 2.5 times fainter? 

 

if so...that doenst seem like much...

 

Hard to estimate. At least two magnitudes. Maybe four. When I look at the bowl of the Little Dipper naked eye from my back yard I just get the faintest star with averted vision. Using my NVD at 1x I see more than a dozen stars within the bowl, down to about magnitude 9 (direct vision), for a gain of four magnitudes.

 

how about frame rates?

 

I have a sony a7s which amplifies light really well with high ISO when in video mode...the downside? its about like 4 FPS.... 

 

Different technology. NV is analog, not digital. Response is instant, no integration times. No trailing when you shift views.

 

 

does that mean you can split very close doubles?

 

 

You can, but not the real use of the tool. Doubles often involve nice color contrasts, and NV is monochrome. I use my standard eyepieces for this.

 

 

One more question. Is it possible to attach a camera like a DSLR to the back side of the NV device such as the PVS7 or mod 3? If so, how big is the image circle?

 

 

Yes, but it starts to get technical. Send a pm to jdbastro about this. He has a great deal of experience in this area.

 

OTOH, many of us are using cell phones to capture images. Very casual and easy. 

IMG_3178.jpg
IMG_3076.jpg
Sh 2-131 Elephant Trunk higher ISO.jpg
HorseHead, e180, 7nm, ISO 4000.jpg
IMG_2645 (1).jpg

  • Starman27 and outofsight like this

#22 joelin

joelin

    Vanguard

  • *****
  • topic starter
  • Posts: 2,143
  • Joined: 14 Jan 2008
  • Loc: Saratoga, CA

Posted 02 December 2019 - 10:54 PM

Cool shots. Can you do long exposures through NVD and stack them for even better astro photos?

#23 TOMDEY

TOMDEY

    Fly Me to the Moon

  • *****
  • Posts: 5,165
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 02 December 2019 - 11:55 PM

when you say seeing a magnitude deeper....are you saying like one magnitude on the scale where its 2.5 times fainter? 

 

if so...that doenst seem like much...

Oh, it's a lot more (see the table) >>> Note that each jump of one magnitude threshold shows you four times as many stars in the same field at the same magnification (and the brighter ones also become much brighter). And I am intentionally being conservative in my claim. The actual improvement may be closer to two magnitudes. It's the sorta thing one has just gota stop imagining and dive in and experience to appreciate. Time to decide?    Tom

Attached Thumbnails

  • 41 star magnitude table.jpg


#24 GOLGO13

GOLGO13

    Aurora

  • *****
  • Posts: 4,543
  • Joined: 05 Nov 2005
  • Loc: West Virginia

Posted 03 December 2019 - 02:58 PM

I have an NV device and do not much fancy it. A modern Mod3C high-spec green film unit kitted to run w/ or w/o various filters and w/ or w/o a scope, the presentation is poor. Resolution is poor. It is nothing like an eyepiece at all. It does amplify the light and shows an image of fainter objects than are seen w/o it but that image does not satisfy my expectations.

 

However, it is quite a bit of fun to sit on the 2nd floor deck of friends' lake house in central Texas on a dark overcast night and let their children watch deer and raccoons move across the property and head down to the lake. Viewed just before sunup, the ashes of a campfire that is long "out" glow brightly in the center, showing  that a fire long burned down retains heat for many hours.

 

The FOV depends on how it is set up.

 

Contrast lags far behind an eyepiece view via any of my scopes and is not like a photographic image except for those low-res ones captured via NV device.

One tricky thing about your setup is the NV monocular you got didn't have the specs with it (I believe looking at past posts). So it would be interesting to compare it to someone else's unit to see if it just isn't a good one for astronomy. This would be a lesson in needing to know the specs ahead of time. In fact, I bought mine not fully knowing the specs until they were provided later. Luckily the specs were fairly good when I did get them. Probably not the top end tube but certainly decent.

 

However, I do agree that in my situation I also feel like the resolution is slightly less when comparing my memory of a dark sky and an eyepiece on nebulas. Such as, the Lagoon at the Okie Tex Star Party in my 10 inch dob and a 5 inch refractor was more detailed than the NV in my orange light pollution. However, it's not too far off for this object. Possibly my unit is of better quality but I don't know that for sure. Based on some of your early observations it seems like you were not seeing details that I am. Then again, I am in slightly darker skies.

 

Now, on things like globular clusters, so far I have much better memories of these in dark skies than NV in light pollution. However, the magnification is totally different and I'm unsure as to what's the best way to observe them. For instance, The NV is probably at 20x and I usually observed them at 48x and 170x.

 

All of this being said, comparing NV to eyepiece in my orange light pollution sky is night and day. There is hardly anything to see in the light pollution with the eyepiece even in my 10 inch dob. Whereas the NV shows basically dark sky conditions from my memory. Just not quite the detail I remember from actual dark sky observing with eyepieces. I have not had the chance to use it in a dark sky though...and I believe that will make a big difference.

 

This discussion maybe the only warning I have for NV...make sure you get a unit from a reputable dealer that provides you the specs. And find out from folks on here what would be considered the minimum specs you would want for astronomy. That makes it a bit of a tricky scenario. It does seem like the units sold by TeleVue and TNVC should be a fairly safe bet...but I would still want to know the specs if possible.


  • havasman likes this

#25 havasman

havasman

    Voyager 1

  • ****-
  • Posts: 10,069
  • Joined: 04 Aug 2013
  • Loc: Dallas, Texas

Posted 03 December 2019 - 03:16 PM

One tricky thing about your setup is the NV monocular you got didn't have the specs with it (I believe looking at past posts). So it would be interesting to compare it to someone else's unit to see if it just isn't a good one for astronomy. 

 

Possibly my unit is of better quality but I don't know that for sure. Based on some of your early observations it seems like you were not seeing details that I am. Then again, I am in slightly darker skies.

Thank you for your post. You make good points that resonate with me. Yes, I bought the device primarily to use from my very light polluted home as I was unavoidably limited to observing from here for the summer/fall months. I was extremely surprised and disappointed with what I saw, particularly after reading the hyperbolic reviews of others' NV experiences.

 

i have a proposal for you that I'll send you in a PM. It may be tomorrow before I get to it as I have a busy afternoon that must be attended to now.




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


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics