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RogerRZ
Whatta you lookin' at?
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Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2180632 - 02/10/08 07:40 AM

I had a TV102, and the in-focus images were so nice, that I never once considered ovserving with it out of focus. I suspect the NP101 is the same.

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sixela
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Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2181302 - 02/10/08 02:22 PM

Quote:


I have a doublet TV 102, so what's your issue?





This snippet:
Quote:

I confirmed this with a simple but all-telling star test, where I once compared a TV 101 with a TV102. The 102 won hands down and showed a level of SA correction < 1/8th wave ptv. The 101 was more like 1/5th wave, which is enough to take the edge off fine planetary detail.




Given that you describe the star testing as "simple" and given your subsequent general comments about star testing, I have doubts as to the rigour which which you came to assess the 101's performance.

Which *is* the subject of the thread, after all.


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Dirtyharry
member


Reged: 11/01/07

Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2181637 - 02/10/08 04:39 PM

Hi Sixela,

On the matter of the TV 101, it has already been asserted that the 102 has sharper optics than the Genesis SDF (see the astromart review comparing them both)and that critical assessment by observers I trust (Ed Ting and Phil Harrington) both agreed that the 102 was sharper optically than the 101(despite it having marginally better color correction). As my threads already discussed, I confirmed this visually on Jupiter by comparing both the 102 and 101 images on the same night. Both gave excellent images, but the 101 was slightly softer IMO. No amount of optical theory can alter my own conclusions. Or, in the immortal words of the celebrated English poet John Keats, " Nothing is real until it is experienced"


Harry


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skyview
Pooh-Bah


Reged: 02/01/06

Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2181894 - 02/10/08 06:35 PM

Late to the party here but thanks for the article Tom, as always it was very thorough and well done. Being lucky enough to own an NP101 I was almost tempted not to read the article as I pretty much knew what would be said; although, it never hurts to be reminded of what an absolute gem this scope is. I always find it somewhat strange and often amusing that when the ubiquitous "best 4 inch APO" posts come up that the NP101 is mentioned as infrequently as it is. Perhaps the only thing better than an NP101 is an NP127, but thats another debate.

Overall my minimal gripes with the NP101 would be:
1) Length, as you mentioned, due to its optical design its functionally an F5.4 but in a slower body
2) Price (worth it IMO), which may keep it out of deserving hands
3) May requires use of well made, designed, and perhaps expensive EPs depending on your viewing habits. This may be more of a problem with fast scopes in general but I really noticed a difference in EP performance between my TV76 (f6.3) and the NP101, some EPs didnt work as well in the NP101. Perhaps I am overly sensitive to these things.

As an aside, I would like to add that I too have the focusmate with the driver and will echo how well it works. It may not be the most elegant looking device but I think it works with the scopes aesthetics and it is extremely functional. It also can handle heavy loads, it tolerates my use of a denkII with twin pan24s with no obvious problem.

As a further aside did anyone in the central Ontario (east of Toronto) region do anything to make the astro gods especially furious? I havent had decent viewing conditions for months, I'm not kidding. If its not snow, its fog, if its not fog its wind. Come on, admit what you did and repent. Of course, in retrospect it could be all my fault as the viewing has gone down hill since I waitlisted a Mach1. Is there an "eventually new equipment curse" I dont know about that strikes those who dare sign up for things that wont be available for potentially years. Makes me wonder what the skies will be like when the Mach1 makes its way to my backyard, I expect "black hole" and near-earth orbit" to be prominent in the vocabulary of any survivors who dare speak of it.

Back to topic: Well Done Tom.


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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2181957 - 02/10/08 07:03 PM

Quote:

Hi Sixela,

On the matter of the TV 101, it has already been asserted that the 102 has sharper optics than the Genesis SDF (see the astromart review comparing them both)and that critical assessment by observers I trust (Ed Ting and Phil Harrington) both agreed that the 102 was sharper optically than the 101(despite it having marginally better color correction). As my threads already discussed, I confirmed this visually on Jupiter by comparing both the 102 and 101 images on the same night. Both gave excellent images, but the 101 was slightly softer IMO. No amount of optical theory can alter my own conclusions. Or, in the immortal words of the celebrated English poet John Keats, " Nothing is real until it is experienced"


Harry




Hi Harry,

I'd also (re)state that it's the NP101 we're talking about here - not the 101. I'd basically agree with those statements in the context with the TV102 and the SDF and TV101. In fact, if you go back to the ask-al section on the TV website he has some comments on the relative performance of those scopes too.

Having owned a TV102 for 6 some years, a Genesis SDF for a time concurrently with the 102 (and having a fairly significant baseline of other telescopes come across my desk or viewed through in the field - including the TV101), I can say that the SDF came close to the TV102, while the sample I have of the NP outperforms the 102.

As it's been noted, star testing apos can be somewhat problematic, and for the typical observer I suggest a comparison of the in-focus images. One very important thing to keep in mind: Focus depth is noticeably shallower with the NP tho, so I can see where one might easily come to your results given a single night of comparison if one is not careful of focus and the NP is not equipped with a fine focuser.

As to your statements about Ed Ting and Phil Harrington, I think you might be a bit confused as to the TV101 (previous generation) and the NP101 (current generation about which this article was written).

As per Phil Harrington in the 4th (current edition) of Starware (pg 104), he writes:

Quote:


No doubt about it, Nagler has done it again. The NP101 is an amazing optical accomplishment setting bar by which all other apochromatic refractors are judged.

This level of excellence does not detract from the TV102, which is an exceptional performer in it's own right. But in side by side tests conducted at Riverside Astronomy Expo, I found it is not in the same league as the NP101.





(emphasis mine)

Additionally, Ed Ting compared the TV102 to a TV101 and SDF, not an NP101 as can be seen here:

http://www.scopereviews.com/page1k.html

Where he makes very similar statements to what I do regarding the relative performance of the SDF and the 102.

To the best of my knowledge, Ed has nothing written up on the NP - certainly not on his website, and I can't recall any print articles.

To be fair, there seems to be a LOT of confusion regarding the NP101 and it's predecessor the TV101. The NP replaced the TV101 several years back. It is a different telescope, and should not be judged the same as it's predecessors. The TV101, while also a fine telescope belongs to an older generation and does not represent the pinnacle that the NP does.

Perhaps TV should have named the NP, the Not your fathers TV101 - 101.

Incidentally, I find it interesting Al waited till this scope to put his name on it. From what I understand the MPT, Rennaisance, the Genesis, the Genesis SDF, and the Tele Vue 101 were also Nagler variants on Joseph Petzval's design, but only this one is the Nagler Petzval 101. If you look at the history of the company, Al has chosen to put his name on only truly revolutionary designs - the Nagler Eyepieces and the Nagler zooms. Now he's lent it to the current design of the np101 and np127. I suspect that was not an accident.

T


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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2182017 - 02/10/08 07:21 PM

Thanks for the comments folks, they really are appreciated.

T


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gripweed44
Pooh-Bah
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Reged: 02/12/05

Loc: PDX
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2182685 - 02/10/08 11:44 PM

If a focuser focus's
Is it not in focus?

Focus in the EYE of the observer is what matters
RP or CRAY- what does it matter if it works--

for you


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jonnyastro
Carpal Tunnel
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Reged: 02/14/06

Loc: Pittsburgh, PA
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2183658 - 02/11/08 01:29 PM

I would add that Dickinson and Dyer in , "The Back Yard Astronomer", also alluded to the NP101s superiority to the TV102 visually, stating, "optics don"t get any better than this".

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Dirtyharry
member


Reged: 11/01/07

Re: CN Report: The Tele Vue NP101 new [Re: jonnyastro]
      #2184314 - 02/11/08 06:33 PM

OK guys, I get the message! Much as the NP101 is a nice piece of kit,I won't be parting with my TV102 anytime soon!

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Tom TAdministrator

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Reged: 02/26/02

Re: CN Report: The Tele Vue NP101 new [Re: Dirtyharry]
      #2184318 - 02/11/08 06:36 PM

Heaven forbid! Harry, the 102 is a world class apo in it's own right. Mine was an excellent piece of kit that gave me many many happy hours under the stars.

T


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karim
super member


Reged: 11/09/05

Loc: HB, California
Re: CN Report: The Tele Vue NP101 new [Re: Tom T]
      #2188652 - 02/13/08 12:27 PM

I agree with Tom, the FSQ is mostly used for astrophotography, whereas the NP101 (or TV102 to that matter) is visual.

IMHO, the NP101 is to TV102 what C9.25 is to C10.


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Daniel Mounsey
Vendor (Woodland Hills)
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Reged: 06/12/02

Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2195248 - 02/16/08 02:39 AM

Quote:


But this is really off-topic: if you want a discussion about this, the ATM and Optics forum is the place for it, or you can try Astromart if you feel like getting spanked by Roland himself.





Hi Alexis,

Tom T. mentioned some interesting points about the in-focus star test and light outside the airy disc which I found to be quite valid. Just thought I'd share some experiences I had during some observations I made. I have always respected your views and continue to, so I'm attempting to share some observations I made while testing a good number of 4" apo refractors and in this case, two, three and even four of the same exact ones on the same night at the same time. I also had some personal discussions with Markus Ludus at NEAF about the star test, in fact I just recently star tested a new FSQ106 Q for Markus before I sent it to him but let me address something first. I actually don't care what the papers say. If I can't observe the differences myself, then I don't bother.

There is actually quite a bit of difference of opinion in this industry regarding star tests these days. Since we know there are so many orders of spherical aberration, there needs to be some clarification. For example, there have been discussions about differences in the star test being visible outside of focus but not in-focus. But I ask by what standards are these images the same from a visual standpoint? What do they define as absolutely excellent? In other words it's a bit vague.

Here are some observations I made. I took two of the same scopes and focused them on the Trapezium in Orion under excellent seeing conditions. Each one was star tested on a brighter star first and then placed on the Trapezium. I want to make it clear to others that the point of using the Trapezium as a target was NOT about splitting the components as it is not a valid test. The key was to observe and study the contrast between the components and observe the strength of the light in and around the airy discs, particularly the E and F component stars. In some of the refractors I tested, a good number of them did not direct a strong amount of light in the airy discs of the fainter E and F components compared to others and the differences were quite startling to my eyes to say the least!

I'm a custom wood case builder. I can purchase three sheets of A-1 birch ply and build three of the same cases but they still will have subtle differences which can be observed. It's just simply impossible to get every one literally, exactly identical and high quality apos are no different and easily proved to be so during my critical tests with the human eye. In every single case with my tests, the star test proved absolutely dead accurate to what was observed with the in-focus image on the Trapezium and particulary the planets. In other words any optic which exibited a slightly higher degree of under-correction, proved to scatter more light outside the airy disc.

It's just simply impossible for opticians to make every optic exactly the same and thus, observers end up discussing various orders of spherical aberration, but at critical levels of observations, they are still aberrations, they still exist and some can be detected visually. My point is that three scopes with three slightly different star tests will all have a different level or degree of contrast. They are not going to be the same while trying to descern very fine planetary details and that defference will most easily be noticed side by side on the same night. My visual tests clearly validated this. BTW, the NP101's I tested were incredibly consistant in optical quality in that regard. I can understand why Tom likes the NP101, it proved to be a good scope during my observations as well.

Clear Skies!


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sixela
Postmaster
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Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 *DELETED* new [Re: Daniel Mounsey]
      #2195282 - 02/16/08 03:26 AM

Post deleted by sixela

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sixela
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Reged: 12/23/04

Loc: Boechout, Belgium
Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2195285 - 02/16/08 03:34 AM

Quote:

The key was to observe and study the contrast between the components and observe the strength of the light in and around the airy discs, particularly the E and F component stars. In some of the refractors I tested, a good number of them did not direct a strong amount of light in the airy discs of the fainter E and F components compared to others




I have no issue with that - that's eating the pudding, which is its proof. Performance *in* focus is what counts. What isn't simple is correctly interpreting the *out* of focus star images.

Doing an in-focus star test isn't as simple as it sounds either, by the way, at least not if you want to detect 1/8th wave of spherical aberration. Refractors need to cool as well and will typically show spherical aberration before they're perfectly cooled (the aberrations are nowhere near as ugly a on an uncooled Newtonian, but they do exist).

Quote:


My point is that three scopes with three slightly different star tests will all have a different level or degree of contrast.




If you're talking about the in-focus star test, yes. If you're talking about out of focus star test images, though, it's possible for the three scopes to have very different *out* of focus star test images and still perform identically in the *in*-focus star test. Yes, in theory what you're seeing are aberrations, but I doubt you can see them if the effect in focus is to reduce the Strehl ratio by 0.003. *Some* aberrations are much more visible out of focus than in focus, and that's the danger.


Mind you, even out of focus it's *possible* to discriminate between different orders of e.g. spherical aberration by the way ring patterns *evolve* around focus. But it certainly isn't simple.


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Daniel Mounsey
Vendor (Woodland Hills)
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Reged: 06/12/02

Re: CN Report: The Tele Vue NP101 new [Re: sixela]
      #2219435 - 02/26/08 12:46 AM

Hi Alexis,

Forgive me taking so long to get back to this forum. My time has been very limited lately. I don't make any claims regarding Strehl ratios or wavefronts based on visual observations. They mean very little to me.

The issue I'm having with the star test is that since sophisticated triplets have hit the market, opticians have placed contradicting emphasis on the in-focus image and my tests clearly proved that the star test works only one way and that is, that both sides look exactly as close to the same as possible. Obviously there are limitations to this. It's just simply impossible for opticians to make every single lens the same in that manner, not to mention the various temperatures they are exposed to causing differences as well.

As you and I both know, refractors by their very nature will exhibit under-correction throughout the cooling process and it's a safer state for the optic to be in. My FS152 produces a slightly different star tests under various temperatures but the problem I'm having regarding this matter is that some opticians are trying to convince observers that two of the same refractors, one producing under correction and one that isn't are going to produce the same image and that just doesn't fly with me and my tests clearly proved it.

Most observers don't notice it and would be quite satisfied and understandably so. Focusing both instruments on a planet will reveal subtle differences that most observers seeing conditions would rarely allow them to see, not to mention that they'd need two of the same scope to see it more easily. Those last remaining hard outlines on lunar and planetary images can not be the same.

When I listen to some of the things I hear about this new star test, it begins to remind me of the magic bullet theory during the JFK assassination. Since opticians can not make all lenses the same, they have to come up with a reason as to why and those reasons have become a bit misleading. I'd be more than happy to discuss this issue with any optician. There's really nothing to debate though, all one has to do is simply look and see for themselves. Some optics are and "A" and there are some that are just a freak of nature that are an "A+" and they are the rare ones that purist would appreciate, provided their conditions allow.


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