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Rich Field Scope vs NV

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#1 JimP

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Posted 21 October 2021 - 08:45 AM

Hello all,

I recently sold one of my 5 inch refractors and was thinking of replacing it with something that would allow a wider view of the sky for visual Rich field observing. I have a Televue NP101 and was thinking of trying to find a used 127 or something similar. Someone mentioned night vision technology and I remembered many many years ago using a Collins I-3 Eyepiece with my AP 155F/7. I liked it but was somewhat disappointed with it’s inability to show galaxies significantly better than the view without the Collins eyepiece. Somehow, I ended up putting it away and just came upon it during a long search. Looking into what is available today I have been quite impressed with the white phosphorus scopes, particularly the one available at Televue. I would be interested in anyone’s thoughts for or against getting something like an NP 127 vs a white phosphorus setup like the one at Televue.

JimP


Edited by JimP, 21 October 2021 - 08:46 AM.


#2 bobhen

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Posted 21 October 2021 - 09:32 AM

I’ve been observing for 40 years. I’ve been using Night Vision for over 5 years.

 

I cannot stress this enough. There is no and I mean “NO COMPARISON” between using a rich field telescope purely visually and using a rich field telescope with today’s image intensifiers. It’s not even a close comparison.

 

A new TV 127 is what $7,000. You can get an Orion 120mm F5 achromat with extras, a Mod 3 image intensifier with gain control in white or a green tube with very good specs, 2 filters, a 685 Pass for non-nebula objects and a 6nm Astronomic Ha filter for nebulas and it will actually cost less. And you will see so much more.

 

I don’t know what is available these days, But between the TV PVS-14 and a Mod 3 with equal tube specs I would pick the Mod 3 because the housing is more flexible allowing for both prime focus observing (without eyepieces) and afocal observing with eyepieces in the optical train. Whereas, the PVS-14 only allows for afocal observing.

But people like both systems and the views will be similar depending on the tube.

 

I happen to use prime focus and the optical train and optical stack without any eyepieces in the optical train is lighter, not as tall and less cumbersome.

 

Generally… Galaxies need focal length (image scale). For galaxy observing with Night Vision and globulars and small objects in general, I don’t use my fast refractors I use a C8.

 

The power of Night Vision, ease of use on a manually driven alt/az mount, ability to cut through light pollution and show objects that were previously invisible or needed averted imagination cannot be overstated. 

 

Below is my optical train using a 102mm F5 refractor and the Micro Image Intensifier. From left to right...

 

1. Refractor OTA
2. GSO 2” focuser
3. AP 2" Diagonal
4. 2" .7 reducer (optional)
5. 1.25" to 2" diagonal adapter
6. 1.25" filter (Pass or Ha)
7. C-mount to 1.25” adapter attached to the intensifier
8. NVD Micro image intensifier

 

You might want to read a few observing reports in the NV forum. 

HERE is First Night Vision observing report. 

 

Bob

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Edited by bobhen, 21 October 2021 - 10:35 AM.

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#3 GOLGO13

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Posted 21 October 2021 - 10:05 AM

The NP127 should be wonderful with night vision and visual. Overkill maybe, but it would be a great scope for doing all kinds of astronomy!
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#4 ButterFly

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Posted 21 October 2021 - 03:15 PM

Between a Maserati and a helicopter, the answer is both.  Maserati out the helicopter before it lands!

 

A 127mm aperture is not good for many galaxies either, either visually or with NV.  I use a 15" aperture for galxies for visual and NV.  A 40" would be better.  Aperture is resolution.  On the other hand, resolution in near-IR is half that in blue.  If it can be seen visually, it's better resolved for some given aperture.  H-alpha cannot be seen visually, even on the brightest nebulae such as the Swan or Orion, and it's not blue.  The helicopter can go where the Maserati can't.  An NP101 with an H-alpha filter would do just fine at just over f/5 with a nearly 5 degree field using a 67PP.  The 127 would give about a 4 degree field.

 

Sure, you can use the 127 to look at globs, but get an 8" reflector for that.  More resolved and more reach.  A 40" is even more resolved with even more reach.  Galaxies do better unfiltered, so either will do better at a dark site than in a city.  Even with h-alpha, the dark regions are darker at a dark site.  I get more mottling in nebulae from a dark site, even with a 3nm filter.

 

The uses are so disparate that you need to consider what the goals are of each.  For galaxies specifically, I'd say neither.



#5 JimP

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Posted 21 October 2021 - 03:56 PM

I didn’t suggest either one was good for galaxies. What I said was many many years ago I had a Collins I-3 eyepiece which I used with my AP 155F/7 and compared to what it did on other deep sky objects I was just disappointed with what it did on galaxies. That’s all.

 

I don’t know but I suspect the new white phosphorus Night vision equipment will not do any better on galaxies than the old Collins I-3. Sounds like I am right.

 

As for telescopes, I’ve been observing for over 55 years and I have become a refractor fan and I’m not interested in large reflectors. My interest for virtually the entire 55 years has been on high resolution objects like the moon, planets and double stars and my refractors have performed beautifully on those objects. I have only recently gotten interested in rich field visual observing And was considering getting a larger aperture Richfield Scope when someone mentioned  night vision. The person suggested I come over to the night vision site and ask questions which is what I did.

 

Best,

 

JimP



#6 GOLGO13

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Posted 21 October 2021 - 05:39 PM

Galaxies get a little help with Night vision in light polluted skies, but personally I wouldn't buy night vision for Galaxies. EAA would be a better choice.

Night Vision is very good for most nebulas (but not all) and general star clusters. Especially good for sweeping the Milky Way.
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#7 ButterFly

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Posted 21 October 2021 - 06:38 PM

I didn’t suggest either one was good for galaxies. What I said was many many years ago I had a Collins I-3 eyepiece which I used with my AP 155F/7 and compared to what it did on other deep sky objects I was just disappointed with what it did on galaxies. That’s all.

 

I don’t know but I suspect the new white phosphorus Night vision equipment will not do any better on galaxies than the old Collins I-3. Sounds like I am right.

 

As for telescopes, I’ve been observing for over 55 years and I have become a refractor fan and I’m not interested in large reflectors. My interest for virtually the entire 55 years has been on high resolution objects like the moon, planets and double stars and my refractors have performed beautifully on those objects. I have only recently gotten interested in rich field visual observing And was considering getting a larger aperture Richfield Scope when someone mentioned  night vision. The person suggested I come over to the night vision site and ask questions which is what I did.

 

Best,

 

JimP

For point sources, double the aperture in your sky conditions is a good estimate of reach.  I've been doing little fasteroids in the 16-17th mag range from home with my 15".  From a dark site, 19th mag is possible with good transparency.

 

For just star fields, the 101 would be great.  My 80mm has a focal length of about 480mm.  I'm stuck in afocal with a PVS14.  The 67PP gives me a 5.5 degree field.  There are a lot of stars, but there is no color.  Same sky background issues limit magnitude as with bare eyepiece.  And for point sources, f/ratio doesn't matter as much, so my 120mm f/7.5 does fine as well.  The advantage of a Petzval with NV is sharp stars to the edge.  However, point spread functions are twice as big in near-IR as in blue, so the tolerance leaves a lot of room.  The advantage of a Petzval without NV is sharp stars to the edge, that show their color.  Carbon stars and refractors are great, but aperture limits their reach.


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#8 Jethro7

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Posted 21 October 2021 - 07:29 PM

Hello all,

I recently sold one of my 5 inch refractors and was thinking of replacing it with something that would allow a wider view of the sky for visual Rich field observing. I have a Televue NP101 and was thinking of trying to find a used 127 or something similar. Someone mentioned night vision technology and I remembered many many years ago using a Collins I-3 Eyepiece with my AP 155F/7. I liked it but was somewhat disappointed with it’s inability to show galaxies significantly better than the view without the Collins eyepiece. Somehow, I ended up putting it away and just came upon it during a long search. Looking into what is available today I have been quite impressed with the white phosphorus scopes, particularly the one available at Televue. I would be interested in anyone’s thoughts for or against getting something like an NP 127 vs a white phosphorus setup like the one at Televue.

JimP

Hello JimP,

I wont add anything to this discusion, it has been well covered, other than this. "Pictures are worth a thousand words" 

 

Here is a view of the Sagitarius Star cloud region one of the busiest portions of the sky.

Using a Starwave 152mm F/5.9 plus a .07X reducer TV 67 Plossl under Bortle 8 Skies. Not much going on here.

20210925 193500
 
The same view with the same refractor, reducer and eyepiece. Add a PVS 14 Gen 3 unfilmed WPT night vision device plus a 685Nm IR Longpass filter into the mix and you can see this.  Just look at all those stars. This is only a small sample, It gets far more amazing than this. Like being able to actually view Barnards Loop for starters.
20210924 201637
 
P.S. these Night vision devices are a total game changer. A very powerful tool for those of us that live under heavy light pollution and magical if used under dark skies.  I highly reccomend getting a night vision device. This was definatly the best money that I have ever for an Astronomy gadget.
 
HAPPY SKIES AND KEEP LOOKING UP Jethro

 

 


Edited by Jethro7, 21 October 2021 - 07:41 PM.

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#9 bobhen

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Posted 22 October 2021 - 05:24 AM

For the ultimate wide field views, many NV users use camera lenses. 

 

HERE is just one such observing report.

 

Below is my 50mm guide scope repurposed for use with my intensifier. The guide scope/intensifier can be handheld. With that system and from my heavily light polled location (Bortle 8-9), I have glimpsed the brighter sections of Barnard's Loop. which says a lot.  The Rosette, North American Nebula, California Nebula and the Dark Nebula that run through Sagittarius among other such large objects.

 

Like the many who have made the leap, I'm sure you will be thrilled by the Night Vision visual experience. 

 

Good Luck

 

Bob

 

 

 

 

 

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#10 Mort H

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Posted 22 October 2021 - 11:07 AM

Hi JimP,

I'll chime in to say I've joined the ranks of NV observers here in 2021, so maybe several years late to the party but I think the technology is at a point where now is a such a great time to join in!

It's been life-changing for me, best money I've ever spent on astronomy! It's inconceivable to me how anyone with the slightest interest in astronomy would not be blown away by this.

Couple thoughts, if I may...

You mentioned galaxy hunting with a 155 refractor. I think in general that is going to be a pretty huge disappointment. My NV device is fantastic for galaxy hunting, outperforming regular eyepieces. With NV I can see galaxies that are not visible in regular eyepieces, and in bright/large galaxies I can see structure that is not visible in regular eyepieces.

Clearly having a top quality NV device is important here, however that being said, for galaxies there are even more important factors, such as (and theses are just my opinions for whatever it's worth):

- Dark sky, I like Bortle 4 or better to really enjoy galaxy hunting to the max.

- Aperture. For me, 12" is a minimum size to play. More is better. Reflectors are your best friend in this game.

- Transparency. All nights are not created equal.

- Power. Low power is not your friend. (Yet another reason that cries out for a larger scope.)

I would actually list the NV device itself below all the above items in terms of importance for galaxies.

Sounds like you are also getting interested in rich field observing. This is where NV really shines, especially for emission nebulae (because so many are so large...low power is a great fit, and because you can use narrowband H-alpha filters to easily blow your mind even from horribly light polluted locations). NP-101 or NP-127 would be terrific for rich field!

You also were (I think) asking for advice about whether to buy an NP-127 or instead to buy Tele Vue's NV device? (And forgive me if I mis-interpreted.) So I just wanted to clarify that the NV device is something you would use WITH the NP-127 (or any other telescope), not instead of it. So the answer is to buy both!

Also I'm a huge Tele Vue lover, but there are other excellent choices in both telescopes and NV devices, so it may pay to read as many threads as you can here in the NV forum.

I'm on vacation currently, and a few nights ago I spent a simply enchanting evening observing with my 30-year-old son in Yellowstone National Park. (My daughter and grand-daughter live 1 mile from the park, so we are all there visiting for a few weeks.) And just last night my 31-year-old son joined us for another NV astronomy session, he flew in from Chicago. Both boys were really impressed with my NV setup, we were observing just using Canon camera lenses that I had along for vacation anyway (85mm, 135mm, 200mm handheld, and 400mm on a tripod). Just absolutely magical. My younger son has already been raving so much about it, he says he's going to save up until he can buy an NV device for himself! And he previously has not really had any interest to speak of in astronomy, so I think that is quite a testament.

Prior to NV, I really never had a very good way to do astronomy on vacation, space is limited in the camper van. But with NV I'm now able to do some mind-blowing astronomy with a very compact and travel-friendly solution (the camera lenses and tripod were already part of my vacation packing for normal photography).

You have been observing for 55 years? Then like me, you are no spring chicken. How many good years do you and I have left on this planet? Treat yourself, buy an NV device, it will open up worlds you never knew existed. I'm so glad I joined the fun!
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#11 Jim4321

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Posted 22 October 2021 - 12:52 PM

With the proper selection of filters, NV can show you a whole new view of the universe.  The number and size of of hydrogen clouds is pretty well awesome.  For example, seeing the complexity of the Orion Nebula's clouds is awe-inspiring.  I honestly don't recall what if any filters I had in the focal-reduced C9.25 at the time, but I had a splendid view of M51 with my Mod3 and just a hollow 1.25 snout.  It was also great on the Sombrero and M81-82. That's under cruddy SE US skies; dunno where you are.

 

Jim H.


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#12 Dale Eason

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Posted 22 October 2021 - 09:33 PM

With NV you quickly realize that the night sky is more than just a bunch of stars.   For about 3/4 of the year the sky is full of large nebula you never could easily see before.   As others have said it is a game changer.   For 30 years I used scopes that gave me a small field of view of less the 1/2 a degree.   Now with NV there is a reason to go wide field and with the right scope NV will change how your view the universe.

 

For me it also improved galaxy hunting here in my Bortle 8 suburban sky.   It was not until NV did I learn to navigate Virgo and Coma cluster.   In my case I use a 10 inch F3 home made reflector.   It has also enhanced the amount of stars I can see by 10 fold. 

 

 

The difference with modern NV compared to no NV is like the difference to not having a telescope to use in the first place.  It is that astounding.

 

Dale


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#13 JimP

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Posted 23 October 2021 - 06:28 PM

Thanks everyone. I really appreciate all the info you were willing to share with me. Tonight I will be using my Televue 101with and without my old Collins I-3 eyepiece. No, I cannot buy the NV device and a TV 127 but I don’t need to. I am leaning toward the Televue simply because I can get everything I need and I will not need to be looking for this or that adapter. The nightmare would be to buy everything for thousands of dollars I think I need, only to find something I really need is “on back order” or listed as “more to come” (Not). I should be able to try the Collins on multiple objects and compare it to views with just a regular eyepiece. 
 

Thanks again everyone!

 

JimP


Edited by JimP, 23 October 2021 - 06:29 PM.


#14 Dale Eason

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Posted 23 October 2021 - 09:36 PM

Unless you observe in very dark skies NV needs filters.   These are not the ordinary filters that one usually uses with telescopes.   Until we know what the sky conditions are where you observe we can not recommend any.   But the usual ones are narrow band versions of HA and a long pass IR.   Much has been posted about them so I will not go into details other than to say they make all the difference.

 

Dale


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#15 bobhen

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Posted 24 October 2021 - 06:18 AM

Jim,

You WILL NOT get the benefit of NV observing without using filters. The filters are not visual filters they are the very strong filters used for imaging, which shows you just how powerful an intensifier really is.

 

Start with a 6nm Astronomik Ha filter for nebula and a 685 Baader Pass filter for non-nebula objects.

Get the 1.25" or the 2" size depending on what works with your intensifier set up.

 

Those 2 filters are what I use in my Bortle 8-9 sky with excellent results.

 

I believe Baader has also come out with a 6.5nm Ha filter that might be more widely available.

Again, DO NOT make any moves or judgments without using filters.

 

If you have a Collins I-3 that is in excellent working order, then most of your expense is already accounted for. Get the filters!

 

If after you use the filters and for some reason you are still not happy with NV, you can get a good price for a Collins with the accompanying filters.

 

Bob



#16 chemisted

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Posted 24 October 2021 - 06:46 AM

Thanks everyone. I really appreciate all the info you were willing to share with me. Tonight I will be using my Televue 101with and without my old Collins I-3 eyepiece. No, I cannot buy the NV device and a TV 127 but I don’t need to. I am leaning toward the Televue simply because I can get everything I need and I will not need to be looking for this or that adapter. The nightmare would be to buy everything for thousands of dollars I think I need, only to find something I really need is “on back order” or listed as “more to come” (Not). I should be able to try the Collins on multiple objects and compare it to views with just a regular eyepiece. 
 

Thanks again everyone!

 

JimP

That's great; I was hoping you still had the Collins I3.  Remember, Lindy Williams did his ground-breaking observations of nebulae with his (LINK).  As he and others point out a narrow band H-alpha filter is required.  I have the original Collins unit that predates the thin film versions and it still gets lots of use.  Bill Collins did an excellent job of choosing tubes for his eyepieces and I think I can offer some tips for you to get the most out of yours.

 

I will assume that yours has the 1.25" nose and you are simply dropping it into a diagonal.  For nebulae I have used mine with a TV-140 that is the same design as your 101.  The backfocus on mine requires me to use a Baader T-2 diagonal with reducer screwed to the telescope side and the Baader 'Shorty' eyepiece holder to accept the Collins unit.  I screw the Astronomik filter onto the eyepiece and my reducer is a GSO 0.75X.  I haven't owned a 101 but it seems reasonable that it should behave similarly to my 140.

 

I bought my Collins in 2002 so I have nearly twenty years experience using it.  Please contact me with any questions you may have.  Clear Skies and good luck with the intensified viewing!


Edited by chemisted, 24 October 2021 - 06:48 AM.


#17 JimP

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Posted 24 October 2021 - 08:47 AM

Two observatories one has Bortle 4 skies, the other Bortle 7. A third location is also Bortle 4.
Above 4” aperture all my scopes are long focus, F/7 - F/9. None have reducers.

JimP

#18 ButterFly

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Posted 24 October 2021 - 02:21 PM

Two observatories one has Bortle 4 skies, the other Bortle 7. A third location is also Bortle 4.
Above 4” aperture all my scopes are long focus, F/7 - F/9. None have reducers.

JimP

That's still fine for stellar type objects unfiltered.  Try M15 and M2, with and without I3.  Then with and without Moon.  The Moon will show the benefit of the long pass IR, even on stellar type objects, as the background gets higher.  891 is a good galaxy to test unfiltered from Bortle 4, but the Moon will kill that dust lane.

 

My 120mm is f/7.5.  It's a great image scale for filtered nebulae, but it's noticably dimmer than my 80mm f/6 or 15" f/4.78 as paracorr'ed.  Not a deal breaker, but a reducer would brighten than right up, at the cost of image scale.  My 120 is still mostly visual, with only incidental NV use.  The 80mm and the dob are my preferred setups for that, with a factor of four increase in focal length, and thus image scale, at comparable f/ratios.  This is fundamentally an imaging technique, so f/ratio determines how bright the objects are, and aperture determines how resolved the objects are.  Two f/7 scopes are as bright, regardless of aperture, and two 5" scopes are as resolved, regardless of brightness.

 

Filtered Propeller Nebula (PN) is a good comparison between the apertures.  From my Bortle 5 yard and a 6nm filter, the 80mm sees the cloud that it's in, but not the PN.  The 120mm can just barely see the PN, when there is excellent transparency.  The 15" always see it, except when there is very bad transparency.

 

An Astronomik 642 longpass has a bandpass from around 640-850.  It's a great filter for my skies at home without dimming stars too much.  The h-alpha portions still get swamped by background.  The Swan, Orion and Flame nebulae have lots of reflection portion in addition to h-alpha.  Those work unfiltered from Bortle 5, and do much better with the 642.  I like my Baader UHC-S for those.  The background is darker than with the 642, but not as dark as with the narrow h-alpha.  Many more stars get through.  The UHC-S has broad bandpasses around h-beta/OIII out to Carbon lines, and a broad 35nm h-alpha pass.  At my Bortle 2/3 sites, I prefer having UHC-S, 12nm, and 3nm in the slides.  At home, the UHC-S just barely shows the Horsehead.  That prefers a narrow pass.  You may happen to have a similar foter on hand, with an h-alpha pass region, so give it a try if you do.  I'd recommend a 6nm h-alpha to start off with for your Bortle 4 skies, then a 642.

 

Reducers, if you so choose, would leave resolution unchanged, but brighten the image at a lower image scale.  A lower focal length scope at a comparable f/ratio is a perfectly acceptable alternative to reducing one scope.  With extremely narrow h-alpha filtering, these don't need to be APOs.  For unfiltered things, such as globs and galaxies, I prefer the dob anyway.  Rather than the cost of a reducer, a used guide scope is a reasonable alternative for h-alpha filtering.



#19 JimP

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Posted 24 October 2021 - 07:51 PM

Whew! Tough to follow all this but I think just picking out one or two scopes with a couple of filters and see what I can see with what I have is going to be my approach. I never used any filters with the Collins I3 in the past so I think I should see an improvement. As for F ratio controlling brightness I can only follow you when speaking of the same aperture scope at different focal lengths. Why a 120 F/7.5 is dimmer than an 80 F/6 is a little tougher for me unless you are saying the shorter fl scope is working at a lower power and therefore the light is more concentrated in the smaller image.

More to think about.

 

JimP


Edited by JimP, 24 October 2021 - 07:52 PM.


#20 ButterFly

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Posted 25 October 2021 - 02:38 AM

As for F ratio controlling brightness I can only follow you when speaking of the same aperture scope at different focal lengths.

Take that to the next step: same focal length scopes with different apertures.  The collecting area is a lot bigger in the larger aperture scope.  The same focal length means that the image scale is the same, so each sensing element (pixel or retinal cell) gets more light per unit time.

 

With the same aperture, the same amount of light gets collected.  When the same aperture scope has a longer focal length, the image is bigger and that light is more spread out.  Each sensing element thus gets less light per unit time.

 

The "per unit time" is what's important here.  That's why low f/ratio lenses are called "high speed" or "fast".  The amount of light that hits each sensing element per unit time is higher in high speed lenses so pixels get saturated faster.



#21 JimP

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Posted 25 October 2021 - 10:19 AM

Well, a little disappointing. I called Televue and the wait for their night vision system is approximately 20 weeks. I shouldn’t complain but at age 71 I tend to dislike the idea of waiting on anything over a few days.  

Oh well, I have my Collins I3 eyepiece and I have ordered two filters for it.

 

Jim



#22 scoale

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Posted 25 October 2021 - 11:20 AM

Well, a little disappointing. I called Televue and the wait for their night vision system is approximately 20 weeks. I shouldn’t complain but at age 71 I tend to dislike the idea of waiting on anything over a few days.  

Oh well, I have my Collins I3 eyepiece and I have ordered two filters for it.

 

Jim

Hi Jim.  Another alternative, if you are in a hurry, would be to pickup a PVS 14 from a merchant who has one in stock and pair it with the Televue accessories.


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#23 stnagy

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Posted 25 October 2021 - 07:49 PM

For example, Kosher Surplus seems to have some current stock.

https://www.koshersu...sphor-filmless/

Unit 5982 they advertise looks good.

Unit 5982 18UM – SNR: 35.5, Resolution: 72, FOM: 2556, EBI: 0.7, Halo: 0.8, Gain: 64.5k. No spots on the L3 data sheet.


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