23 replies to this topic

[Skyscratcher88]

I have recently become enamored with refractors and have been having fun viewing my favorite DSO’s with my new to me SV127D. I’ve had it out on one very good night at a dark B2 site and was thrilled with it’s performance. M104 “Sombrero” and NGC3242 “Ghost of Jupiter” stole the show that night.

My favorite objects are PNe’s. I have logged over 90 with scopes 6”-20” and enjoy sketching them. The APO is so easy to lift from my garage and walk out into my driveway-home is B5-NV could make this setup ideal from home. I plan on getting a scope buggy to make it even easier.

When I read about NV it seems most observers view large objects with huge-Fl EPs.

I am thinking of placing a deposit for a TEC140. When I get the 140 (2ish years) I’ll sell the SV127D, I know +13mm is going to do essentially nothing but the TEC140 is a dream scope.

NV is something I am considering to extend my range with these relatively small 5-5.5” APOs. Will NV work for PNe at higher powers at small 1.0-0.75 Exit Pupils?

Should I just ditch the 140 idea and stick with my very good Edge800HD? Will NV work well at high power with the SCT?

[GolgafrinchanB]

So, I tried the ring nebula at a 1.1mm exit pupil in my 72mm frac from my bortle 9 skies with no filter just to give an example here. This is the result: https://www.cloudyni...sion-no-filter/ (at 911 KB, I can't directly attach it here).

 

If the idea of this but with less noticeable scintillation is nice to you, then I say go for it. Keep in mind that these are really bad conditions for viewing the ring - but it gives some idea of the expected scintillation levels when viewing stuff at 1.1mm exit pupil. I'd expect a bit more scintillation from a dark site since my light pollution is making the background a bit more grey.

 

If you do a prime focus setup, you can probably get the stars more crisp than my setup.

[Neptune]

The TEC140 was one of the best scopes I've ever owned. Visually you won't notice much difference between a 140 APO and a 8" sct.  Save up for a nice used one.

[bobhen]

I have recently become enamored with refractors and have been having fun viewing my favorite DSO’s with my new to me SV127D. I’ve had it out on one very good night at a dark B2 site and was thrilled with it’s performance. M104 “Sombrero” and NGC3242 “Ghost of Jupiter” stole the show that night.

My favorite objects are PNe’s. I have logged over 90 with scopes 6”-20” and enjoy sketching them. The APO is so easy to lift from my garage and walk out into my driveway-home is B5-NV could make this setup ideal from home. I plan on getting a scope buggy to make it even easier.

When I read about NV it seems most observers view large objects with huge-Fl EPs.

I am thinking of placing a deposit for a TEC140. When I get the 140 (2ish years) I’ll sell the SV127D, I know +13mm is going to do essentially nothing but the TEC140 is a dream scope.

NV is something I am considering to extend my range with these relatively small 5-5.5” APOs. Will NV work for PNe at higher powers at small 1.0-0.75 Exit Pupils?

Should I just ditch the 140 idea and stick with my very good Edge800HD? Will NV work well at high power with the SCT?

If you are specifically buying the TEC 140 for Night Vision use on smaller targets and you want to use higher powers, then keep your C8 and forget the TEC 140. 

 

If you are buying a TEC 140 to replace the SV 127 for visual use, especially on the moon and planets, then save up for the TEC 140.

 

I use a C8 with my image intensifier at both its native F10 FL and reduced to F7 and its great for small targets like galaxies and globulars. 

 

For Night Vision use, I would suggest keeping the C8 but pair it with a fast, inexpensive refractor like a 4" F5 achromat or other fast refractor that will give you wide fields. Then, with the C8, you will have small targets like galaxies and globulars covered and, with the fast refractor, you'll have large targets covered, like huge, sprawling nebulas, like the North America Nebula, etc.

 

Below is how I use my C8 and my fast, 4" F5 refractor with Night Vision.

 

Good luck

 

Bob

Attached Thumbnails

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[GeezerGazer]

For 30+ years, I was a refractor guy using my TeleVue, TAK and TEC scopes visually only.  I happily used a TEC 140 visually with glass eyepieces for 12 yrs, and I purchased my Mod 3C specifically for use with it.  When I started using NV in late 2016, I used the 140 both in prime focus and afocal.  I settled on prime use for its convenience, and in 2018, I bought an inexpensive 8" f:3.9 CF Newt and an Ackermann .73x reducer/corrector providing an effective f:2.8 focal ratio.  The difference (visual and phonetography improvement) was startling.  By 2019, I sold my TEC 140 because I had stopped using it, along with most of my prized glass eyepieces, and began concentrating mostly on NV phonetography.  In 2023/24, I sold the 8" Newt (downsized... I'm in my late 70's), replacing it with a 6" f:4 CarbonStar Newt with the .73x reducer/corrector (f:2.9), AND an 8" SCT for planetaries, globs & galaxies.  I still have a 115mm APO refractor, but it is seldom used.  I also use 5 old Nikon camera lenses with focal lengths from 24-300 mm, for extremely wide angle NV photos in prime focus.  

 

It's not that the NV views through the f:7 TEC 140 were bad, heck, NV seemed to double the aperture of this scope on most subject matter (who wouldn't like looking through a 280mm APO?), but the views through the f:2.8 ES 8" Newt were better, brighter with less scintillation/electronic noise providing a very wide FoV to see more big nebulae.  Because I could actually see nebulae, they became some of my favorite subject matter.  With the TEC (before NV), I had been able to see and study only the brightest nebulae, concentrating most of the time on what the APO refractor showed best, including planets/luna, double stars and open clusters, with just a few globs resolving into point light sources.  After I acquired NV, aperture and the speedier focal ratio became advantages for NV used in prime focus, that cannot be achieved with the TEC 140... unless you choose to use it in afocal.  How you intend to use your NVD along with personal preferences, should guide your decisions on optical equipment selection.  

 

Before 2018, I never intended to do astro-photography.  Now, phonetography is about all I do because it provides a better image for my aging eyes, it's fast with just seconds or minutes of exposure, and it's done with my iPhone which is relatively simple to use and always on hand.  Here's a link to a few images:  https://www.cloudyni...59-geezergazer/  

 

Goals can change, so I recommend choosing an NVD that permits easily switching between prime focus and afocal use.  I also recommend that you peruse some of the threads in the BEST of NV (pinned at the beginning of the forum listings), specifically for information about lenses/optics and especially differences between afocal and prime focus applications.  You will learn how long focal length eyepieces used in afocal with NV provide faster focal ratios and how prime focus and afocal are different, requiring different optical selections. 

 

It's not complicated, but to make an informed decision, you must understand the choices you make lead you down different paths.  

Good Luck.

Ray

Edited by GeezerGazer, 22 May 2025 - 02:12 PM.

[WheezyGod]

It’s not going to be as impactful on smaller targets because night vision performs better at lower focal ratios. That isn’t to say it won’t help, it just won’t be as much of an incremental impact.

With PN it works well on some but not all. Depends if it’s mostly Ha nebula or not.

Edited by WheezyGod, 22 May 2025 - 08:29 PM.

[Skyscratcher88]

Thanks everyone for the input!

It appears I might be trying to use the wrong tool (refractors @5-6”) for viewing planetary nebula. I have a 20”F5 dob and that shows PNe REALLY well! For example NGC6543 the “CatsEye Nebula” one night when all the variables lined up at 510x 1mm exit pupil showed amazing detail holographic in nature with very subtle but definite colors-robin egg blue-purplish/brown-pink it blew my mind!

The problem with the dob-it’s huge and takes commitment in order to get it ready for observing. I want the refractor (which is a thing of beauty itself)+NV to bring *some* of that thrill with much less work-roll it out on a scope buggy…

I have pushed my SV127D up to @200-250x on the Eskimo, Ghost of Jupiter, CatsEye, Turtle (Hercules), M27, M57 and I like the view! Of course pushing higher power with the small 5” makes them pretty dim but the sharpness/contrast is very interesting-unique compared to the big dob. I guess from what I’m reading above the addition of NV won’t be of much benefit.

I have a DSV-3 mount coming soon. I can’t wait to set up the 5”apo next to the Edge8” and compare them this summer, maybe by then my frac-fever will pass! I definitely want to get a NV setup soon and give it a go!

Edited by Skyscratcher88, 22 May 2025 - 09:51 PM.

[Skyscratcher88]

@GeezerGazer

That was exactly what I needed to hear! The TEC140 is not what I’m looking for in viewing detail in small DSOs with NV.

[GeezerGazer]

That was exactly what I needed to hear! The TEC140 is not what I’m looking for in viewing detail in small DSOs with NV.

You might have misinterpreted my post.  As with all astronomy optical systems, there are tradeoffs.  Using the TEC 140 in prime focus with NV is not ideal because the scope has a relatively slow focal ratio.  I would suggest that if you do purchase the TEC, that you consider using it with NV in an afocal arrangement to substantially reduce the effective focal ratio for improved NV performance.  Do you understand how an afocal NV system reduces the effective focal ratio of the optical system? This is important to your selection of optics.  

 

This article written by CNer Gavster explains why an NV afocal system is valuable.  Since this post, Gavster has converted some of his NVDs for prime focus, which he now prefers with some of his optical systems.  

https://www.cloudyni...rvations/page-2

 

This article written by CNer Longbond explains some afocal limitations that can be avoided:

https://www.cloudyni...t-about-afocal/

 

In your initial post above, you wrote, "When I read about NV it seems most observers view large objects with huge-Fl EPs."  Using the NVD in prime focus does not involve an eyepiece... the NVD, without an attached lens, becomes the eyepiece, permitting light from the telescope optics to focus directly on the NV sensor.  Using NV in afocal does involve an eyepiece, wherein the NVD with its 1x lens is attached to an eyepiece, which most often has a long focal length.  Doing so permits a bigger TFoV, albeit at lower magnification, but the faster focal ratio is quite valuable for improving NV image performance. 

 

This article by CNer Moshen, explains how NV can be used in prime and afocal:

https://www.cloudyni...r/#entry9193435

 

Nearly all of my H-a observing and phonetography is done at f:2.8 or faster in prime focus.  At f:10 through my SCT, an H-a image can become obscured with scintillation on dim subject matter when adding a narrowband H-a filter.  But  galaxies and globs are quite spectacular because a filter is not needed for these objects.  

 

NV is a VERY valuable astro tool and will permit you to see DSO subject matter that you have not seen before, even with your 20" optics.  But how you choose to use NV for the subject matter you choose to observe, is really important.  

 

You also mentioned that you want your intended system to be more convenient than the 20" Dob.  Convenience and performance are sometimes at odds.  But with NV, you have a host of alternatives.  You want light weight, with fast cool down, using a refractor that does not require regular collimation, for quick views from your yard... without a scope buggy?  Bobhen in post #4 above suggested a 4" f:5 achromat.  For several years, I used a very inexpensive f:5 short tube 120mm Orion achromat doublet; it was $250 new.  Because NV is most sensitive in the NIR, I added a 640nm long pass filter which blocks 90% of the visible light spectrum, eliminating nearly all star bloating caused by chromatic error in the achromat.  In one night I photographed 109 objects during a Messier marathon in AZ using that scope.  It was my main NV travel scope because it was short, light weight, and it cost less than any of my glass eyepieces.  I was beyond pleased with its price to performance ratio.  Mounted on my HAZ 31 goto mount with its CF tripod, the entire setup would be less than 25 lbs.  

 

If a TEC 140 is your dream scope, then order it with the option of cancelling.  In the mean time, buy your NVD and use it with your current scopes.  You will figure out what works and doesn't work, and you will have time to discover your preferences.  

Ray

[Gavster]

It’s personal preference but for 6 inches and smaller I prefer refractors to reflectors for night vision. I have had 2 Takahashi epsilons 130mm f3.3 and have ended up selling them (and will not buy another ). From my direct side by side comparisons there is a material amount of light loss from reflectors with nv (certainly with the tak epsilon) so the effective speed was more like f4.5 rather than f3.3 in terms of brightness/detail shown.

I now use a tak fsq85 and fsq130 combined with an AP 0.75x photo compressor which gives f3.7 speed in prime (which I think is broadly comparable to f2.8 with a reflector) and a rather fast f1.5 in afocal with a 67mm eyepiece. I do have a tec160fl but as GeezerGazer says I find this too slow for nv so just use it for planetary and lunar.

[vicuna]

Thank you for this thread.

 

dang I just spent all of yesterday reading about how great the epsilon is and was about to pull the trigger just somewhat concerned I wouldn’t be able to figure out collimating or getting the adapters and all correct. And don’t want another scope really tbh unless I’m going to get a ton of use out of it.

 

if you don’t mind me jumping in to your thread with a ? (It’s related and so as not to bother anyone with private messages)

 

I currently have a 92mm f6 and 140mm f6.5. (Both are CFF brand - super super nice). I would love to be able to throw an adapter of some sort on. Are these too slow for nebula even for a compressor? How do you know if a photo compressor will be compatible with your scope?

 

I think I remember asking the telescope builder (Catalin Fus) and he said they Ricardi 0.75 reducers are compatible with the scopes…but he recommended to not get one for visual. I probably didn’t explain correctly. Is this similar to what your AP reducer does?

https://www.apm-tele...075-x-m63-small

 

I really thought it was just me…had trouble seeing nebula even with the correct filters. So I just focused on globs and clusters (which has kept me super busy!) I have been using mostly prime mode.

Edited by vicuna, 23 May 2025 - 06:58 AM.

[bobhen]

 

I currently have a 92mm f6 and 140mm f6.5. (Both are CFF brand - super super nice). I would love to be able to throw an adapter of some sort on. Are these too slow for nebula even for a compressor? How do you know if a photo compressor will be compatible with your scope?

 

I think I remember asking the telescope builder (Catalin Fus) and he said they Ricardi 0.75 reducers are compatible with the scopes…but he recommended to not get one for visual. I probably didn’t explain correctly. Is this similar to what your AP reducer does?

https://www.apm-tele...075-x-m63-small

 

I really thought it was just me…had trouble seeing nebula even with the correct filters. So I just focused on globs and clusters (which has kept me super busy!) I have been using mostly prime mode.

F6 and F6.5 are NOT too slow. I use prime observing mode and scopes at F3.5, F5, F7, F7.5 and even F10. I sometimes use a .7, 2" generic reducer.

 

Are you using afocal or prime observing mode?

 

For Nebulas, what filter are you using?

 

I live outside Philadelphia in King of Prussia, so close to you. The sky is Bortle 8+ and extremely light polluted. I use an Astronomiks .6 Ha filter and can see the Horse Head Nebula on any clear night.

 

Bob

Edited by bobhen, 23 May 2025 - 01:49 PM.

[GeezerGazer]

Hi Gavin, I was hoping you would chime in.    It's great to read your point of view... always based on your experience with such a variety of equipment.  

 

At 6" of aperture with NV, I have found my f:4 CarbonStar 150 with its .95x reducer/corrector, and my older Ackermann .73x reducer/corrector (@ f:2.9 in prime focus) to be excellent... at least for phonetography of medium and some large H-a.  It's very light weight, holds collimation well, and provides a very nice image with sharp stars with a relatively bright image for such a diminutive scope.  it's 1/2 the length and fully 1/2 the weight of my former TEC 140.  Compared to my 8" f:4 Newt, the CarbonStar is much easier and lighter to set up and is a better fit on my HAZ 31.  The 6" Newt is simply more convenient at my age!    But it is definitely not best for high magnification on small subject matter.  That's why I have the C8.  

 

In many ways, I do miss my TEC 140.  It was a very good performer with glass eyepieces on non-NV subject matter... Luna, planetary, double stars and open clusters.  Hard to beat a good refractor on those subjects.  With NV in prime focus, I did use it with a Barlow for some pretty good images of galaxies and globs too.  It was reasonably versatile in that regard.  

Ray

Edited by GeezerGazer, 23 May 2025 - 01:00 PM.

[vicuna]

F6 and F6.5 are NOT too slow. I use prime observing mode and scopes at F3.5, F5, F7, F7.5 and even F10. I sometimes use a .7, 2" generic reducer.

 

Are you using afocal or prime observing mode?

 

For Nebulas, what filter are you using?

 

I live outside Philadelphia in King of Prussia, so close to you. The sky is Bortle 8+ and extremely light polluted. I use an Astronomics .6 Ha filter and can see the Horse Head Nebula on any clear night.

 

Bob

thank you Bob

 

I am currently prime observing. I have the ability to do afocal and have a TV-67 and the adapters - but tbh I haven't played with that mode too much.

 

I use a CCD Ha 6nm Astronomik

 

I must be doing something wrong my skies are a little better than yours. like maybe bortle 4/5

[GeezerGazer]

I think I remember asking the telescope builder (Catalin Fus) and he said they Ricardi 0.75 reducers are compatible with the scopes…but he recommended to not get one for visual. I probably didn’t explain correctly. Is this similar to what your AP reducer does?

https://www.apm-tele...075-x-m63-small

vicuna,

Most reducers that are made for refractors are designed to focus incoming light on the flat surface of a camera sensor.  Placing a photo reducer ahead of an NVD in prime focus is a good match because the reducer is very likely designed to remove curvature, providing excellent focus to the EoF on the flat NV sensor.  The same photo reducer would probably not perform well in afocal because it is not designed to accommodate focus through the curved lenses of an eyepiece, causing distortions before the light enters the 1x lens on the NVD... which is likely why Fus recommended not buying the Ricardi reducer for "visual" use (through a glass eyepiece).  

Ray

[vicuna]

Ok I think this is starting to sync in now.

 

so with a TV-67 and my f6, i get 6 x 0.4 = f2.4 - so i am better off with my refractors for lower magnification objects

 

then if I want to zoom in more, with a reducer I get 6 x 0.75 = f4.5. So there I use prime and barlows 

 

then maybe keep an eye out for an ~f4 telescope as my next adventure to get even faster

 

is that correct?

 

tyty (sorry again to jump in your thread…thought it was fairly related)

[GolgafrinchanB]

I'm also under the impression that you CAN use a reducer plus the TV65 IF the image circle of the reducer is at least 48mm, the back-focus of the reducer supports a diagonal, and you're OK with some issues in the edge of the field (which lets be honest, the TV67 already has issues at the edge when paired with night vision). That said, I've only tried a reducer once personally and it was the 0.7 reducer flattener for the AT72EDII which did NOT have 48mm of image circle so it sharply vingyetted with the TV67. As a general rule, reducers are more viable alongside the TV67 on larger scopes. It's just kind of how the image circle sizes work out.

[GeezerGazer]

then if I want to zoom in more, with a reducer I get 6 x 0.75 = f4.5. So there I use prime and barlows 

then maybe keep an eye out for an ~f4 telescope as my next adventure to get even faster

is that correct?

Yes, NV used in afocal can provide a bigger reduction in focal ratio (as you note .4x with your TV 67mm), which is very valuable to optics with moderate to long focal ratios.  High quality reducers used in prime focus are generally limited to a reduction factor of .7x to .8x  

 

You would not use a reducer and Barlow at the same time with any scope, as they serve opposing purposes.  But yes, a Barlow in front of NV in prime focus works very well for higher magnification (which does increase the optical FR) which can lead to increased noise/scintillation.  You have to figure out your tolerance level to these effects.  It's always a balancing act according to personal preference.  In afocal, instead of a Barlow, using a shorter FL eyepiece increases magnification.  You "can" use a Barlow in afocal, but why would you?  It would increase the already long stack from the focuser and would add the additional Barlow lenses to the light path, marginally reducing light throughput and increasing the opportunity for reflections or ghosts.  

Ray

[GeezerGazer]

I'm also under the impression that you CAN use a reducer plus the TV65 IF the image circle of the reducer is at least 48mm, the back-focus of the reducer supports a diagonal, and you're OK with some issues in the edge of the field (which lets be honest, the TV67 already has issues at the edge when paired with night vision). That said, I've only tried a reducer once personally and it was the 0.7 reducer flattener for the AT72EDII which did NOT have 48mm of image circle so it sharply vingyetted with the TV67. As a general rule, reducers are more viable alongside the TV67 on larger scopes. It's just kind of how the image circle sizes work out.

Golga, Yes, using a reducer with an afocal NV system works fine if it's done right.  There might be more current information available, but this link provides a pretty complete explanation of afocal fall off issues (vignetting), with added discussion of using a reducer with NV in afocal.  Afocal EoF distortions, were discussed in an earlier thread. https://www.cloudyni...t-about-afocal/

 

Gavster describes very satisfactory results, placing a reducer in front of an afocal eyepiece with NV, for a brighter visual image... detailed in the above link.  

Ray

[Deadlake]

I also use several f 6/f 6.25 refractors with reducers in afocal mode to produce an effective speed of around f 1.8.

 

I might of missed it being mentioned but to get a usuaable image the NVD needs an aberration free lense attached. The ONVI supplied lense has to many wonky stars at the edge for the above configuration however replacing with a Kowa lense made the optical chain usable.

 

I’d recommend a F6 is triplet with an 

 

AP compressor, 0.75 reduction 

2” BBHS mirror

TV 67 mm plossl

NVD

 

That’s a relatively heavily optical chain, a HZA31 mount can handle the torque of the above components relatively easily.

 

The AP compressor just requires a 2.7” AP adapter to be made for a FT3545 focuser by TS.

 

I would get the TEC 140 mm f12 and use for visual only.

 

Edited by Deadlake, 26 May 2025 - 03:32 PM.

[ABQJeff]

I also live in ~Bortle 5 skies (mpsas 19.5 on average). When I get a chance I will take a look at M57 with my 140mm apo and PVS-14.

As mentioned small and bright (planets, doubles, bright PN) is not the strength of night vision. If you live in relatively dark skies, its main use will be dim galaxies, globulars and of course emission and diffuse nebula (NV’s strength).

Example, using my C11 Edge reduced to F/7 and a 13mm Delite in afocal to give same image scale as visual, for M57 I preferred visual over Night Vision.

Interestingly on Cat’s Eye and Blinking Planetary, Night Vision is very complimentary. A H-a 6nm filter makes the central star and some other structure very visible as it strips away the Oxygen glow.

[Mazerski]

Jeff,

 

If you have the 642 IR filter, use this on M57, NGC40, Eskimo, Cat’s Eye for a different but very nice view.

M42, M17 and M8 look really nice with 642 IR.

[vicuna]

ok so I ordered a 2.7" endcap from Starlight

 

then from AP I ordered: a .75 reducer and a 2" Adapter with Brass Locking Ring

 

then I'll just slip my diagonal into that.

 

- I guess I'll see when it comes in, but this isn't something you change on the fly, right? like you decide before your session if you're gonna do it with the reducer or not?

 

- and then if I am using prime, just to confirm, whatever magnification I get, is what I get and I stay with that for the night...no barlows, etc

 

I figured I will be at ~26x magnification with this configuration. (140mm scope at f6.5 plus reducer = f4.875...so focal length of 682...divided by 26 for the prime night vision = ~26x)

 

- and I will try with the reducer and the TV-67 plossol eyepiece and see what happens.

[vicuna]

update: I got it all up and running.

 

it's actually pretty easy to implement and detach...I would say switching from the AP reducer / 67mm plossol / afocal mode to no reducer and prime mode takes maybe 2 min. and with the way Astro-physics makes its knurling, it's very easy to feel and do in the dark.

 

thank you everyone!