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SV90T vs. TV-85 vs. TMB92SS?

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#1 NHRob

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Posted 10 February 2013 - 07:56 AM

Looking into a 90-102mm class apo for easy visual use.
The 4"+ aperture starts to get bulkier and the 80mm aperture would probably leave me wanting more photons. Wanting 4" class views in a compact package (don't we all!). I figure 90mm range might be a good compromise.
I had a TV85 years ago and enjoyed it. New scopes have since become available and another 5mm aperture wouldn't hurt.

This would be a general purpose, jack-of-all-trades use scope.

Anyway, I can understand the mechanical, build quality, price differences.
What I'm curious about are the optics .... mostly the quality of the optics.
How do they compare? Does anyone have experience in this area, using 2 or 3 of these scopes? Sharpness and contrast?

Thx for any inputs.

Regards,
Rob

#2 tomharri

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Posted 10 February 2013 - 09:34 AM

The Astro Tech 90 f/6.7 is also very good. I have the Burgess version, they seem to all use the same china triplet with fpl53 element. In Jan2010 Mars at 300x was very good for such a small scope.

#3 NHRob

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Posted 12 February 2013 - 08:28 AM

the AT90 looks good but it is heavy.

#4 NHRob

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Posted 12 February 2013 - 08:52 AM

OK, so I'm really leaning towards the SV-90RT. It looks sweet!

#5 Stephen S

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Posted 12 February 2013 - 10:14 AM

OK, so I'm really leaning towards the SV-90RT. It looks sweet!


And at the current sale price, it looks very tempting. I had an 80mm version of this scope and regret having sold it. Both contrast and sharpness of the Raptor were outstanding.

Had I not just recently purchased a TV NP101, I'd have already placed and order for the 90mm Raptor. Still tempted to do so but can't justify having both a 90mm and 101mm telescope at the same time.

Still... so tempting :question:

#6 Widespread

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Posted 12 February 2013 - 04:16 PM

I hope there is still inventory; when the stock runs out, so does the sale. SV ran out of theirs in a couple weeks, I think. Vic said he sent back some bad glass to get it refigured, and when that is corrected and sold, that's all she wrote.

It really is a sweet scope, Stephen. Wanna trade? :grin:

Best,
David

#7 makipper1

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Posted 12 February 2013 - 04:31 PM

Hi, David. I did order an SV90 from OPT yesterday. They did say they had some coming in from Stellarvue at the end of the week. I will confirm for you that I got it.

Mark

#8 Stephen S

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Posted 12 February 2013 - 07:54 PM

It really is a sweet scope, Stephen. Wanna trade? :grin:


:lol: If I did any thing, I'd be looking to build my telescope empire. It's totally justifiable to have both a 90mm and 101mm telescope, correct? Perhaps I should not be asking this question in the refractor forum.

#9 la200o

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Posted 12 February 2013 - 08:31 PM

Stephen S:

I'd go so far as to say that it's totally justifiable to have more than one 101mm telescope!

Bill

#10 nicknacknock

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Posted 13 February 2013 - 04:33 AM

OK, so I'm really leaning towards the SV-90RT. It looks sweet!


Confirming sweetness here! Just had first light with mine last night. You will enjoy the scope!

#11 Eddgie

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Posted 13 February 2013 - 12:48 PM

I have to tell you that even going to a 4" scope from an 80mm scope is not much of a step up.

You may not like the added weight and bulk of a 100mm scope, but stepping to an 90mm scope will make such a small difference in performance that you may find yourself wondering why you bothered.

Otherwise, all three manufacturers you mentioned make high quality telescopes. Flip a coin, or pick the one you think is prettiest. Unless you can differentiate them on mechanicals and price, you really aren't going to find an answer here.

Me, I would go for the TMB simply because it is the biggest of the three. Again, I believe that the optical qualitly will be similar between them, so that means that the only true differentiator in performance will come from aperture, and more aperture is always better.

Quality being equal (which I assume will be the case here), the bigger, the better. Why have an 85mm scope when you can have a 90mm scope, and why have a 90mm scope when you can have a 92mm scope?

I have learned recently that Stellarvue tests their APOs for .95 Strehl minimum (excellent). TMB likewise is known to produce high quality telescopes. Televue I think is a half step behind these others in terms of raw optical quality but I would dismiss it simply because it is just not enough of a difference to see under any circumstances over an 80mm scope.

Good luck with your decision.

#12 Scott Beith

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Posted 13 February 2013 - 02:17 PM

Ed I have to disagree with you on one point sir. I find the jump in performance between a 3" and a 4" refractor to be quite obvious. Well worth the effort and money. That said, I only have 3", 4" and 5" scopes, so I understand your perspective when you use larger scopes and see a larger jump in performance...

#13 la200o

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Posted 13 February 2013 - 02:47 PM

I see a significant difference between 3 and 4 inch scopes; also, I guess I can't quite go along with the idea that TV optics are a "half step behind" the others, at least such has not been my experience. In fact, I doubt if one observer in a hundred could tell a bit of difference between them. I agree, go with the prettiest, and as far as that goes, de gustibus est non disputandum.

Bill

Regards,
Bill

#14 Eddgie

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Posted 13 February 2013 - 05:08 PM

Did not say you could not see a difference, but in my opinion it is not much of a difference.

I usually recommend a 50% increase in aperture to see a meaningful difference at the eyepiece. Sure, I can see the difference between an 80mm and 100mm scope, but it is not a big difference, or it least is wasn't for me personally.

But that is me... Unless I get some kind of serious improvement, I feel like I am half stepping and I get the "well, what was the point of that?" kind of feeling.

As for Televue quality, I have seen numerous bench tests of Televue scopes over the years, and the optics, while excellent, are not quite to the level of some of the other producers.

This is not my opinion, but based on the actual interferometer tests I have seen.

Excellent, but once again, not quite the same level of quality as the TMBs I don't think.

Anyone that wishes to see this for themselves can go to Astro-Foren.de.

Astro-foren.de has tested a number of TMB scopes and the Strehl has always been exceptoinal

They have also tested a couple of Televue scopes, and they have not tested as well as the TMBs. Not that they aren't usually very high quality, but not as good as the TMBs.

I have seen tests from web sites in Japan that have shown the same thing. The Televue scopes often have a slight central zone.

Here is a perfect example:

Televue scope with central zone

Another Televue scope with central zone and Strehl of .93. Only good, not ex...

Yet another Televue scope with a central zone... .95 Strehl.

So, Televue quality has clearly varied over the years and while the scopes are generally good to excellent, I still think they are a half step behind the TMBs which almost always have exceptionally high Strehl.

Again, Pipe has tested many TMBs. Anyone that chooses to do so can spend a half our on his site and judge my evaluation for themselves.

There used to be a Japanese site with tests for the Televue 102 and the NP 127. Once again, both were very high quality optics, but oddly both had the same persistent central zone, though the 102 was almost perfect even with the tiny zone at the center.

You can say that I am wrong of course, but I am only conveying the results that summarize all of the bench tests of the Televue scopes I have seen over the last decade.

Mostly excellent, but still short of the best. The Synta ED scopes have shown (by comparison)better serial production quality, some matching the TMBs. Impressive stuff.

#15 Eddgie

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Posted 13 February 2013 - 05:33 PM

A follow-up to my previous post.. This time the TMB:

TMB 80mm with .994 Strehl

TMB 115 With .99 Strehl in Green

TMB 100 with a flaw in the glass, but still .97 Strehl

TMB 100 with .979 Strehl

Seriously... TMB has tip top quality. Televue, while also generally excellent, is simply a half step behind.

Skywatcher 120 with .979 Strehl

Another Skywatcher 120 with .975 Streh this time

Here is the Stellarvue 90. Outstanding...

Stellarvue 90 with stunning optics

Ok, that is enough. But based on these, I think that my statement that Televue is perhaps a half step behind TMB and Stellarvue is somewhat justified.

Of course these differences in quality between a .95 and .98 scope are impossible to see at the eyepiece.

But a Strehl of .929 is not what I would expect from a top tier manufacturer and Televue has clearly produced some scopes that have not been to the consistently high standards of TMB and maybe Stellarvue. I have not seen enough Stellarvue tests to get a feel for their serial production quality, but I know them to be very high from my own exposure.

And by the way.. There was someone on this very forum a while back with a new Televue scope.. It had a central zone.

I tried to tell the poster that is was likely not serious, but he was upset. And I meant it. I did not think the zone was serious at all.

But he had purchased a "premium" telescope and well, he was very upset. Was he wrong to be upset for a zone that was likely more cosmetic than serious? I guess for what he paid, he expected better than Synta quality.

#16 la200o

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Posted 13 February 2013 - 08:26 PM

Well, I'm not inclined to get into another one of these endless arguments about TV optics; there are plenty of very experienced observers and reviewers who consider them "premium," and equal to just about any other "premium" brand, as do I. Much of this is subjective, or based on limited examples. I remember a thread in which one poster thought that AP refractors were overrated and, I believe he wrote, "hyped."

Again, you can't go wrong with any of these. It's a nice dilemma to have.

Bill

#17 Eddgie

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Posted 14 February 2013 - 10:15 AM

I did not say that they were not premium. Only that from the objective tests I have seen over the last decade, they tend to be slightly behind TMB.

There is absolutely nothing subjective about the data I provided, and Rorh's site has several TMB and Televue tests and based on hard measurements, the TMBs appear to be consistently near perfect.

The Teleuves, while still excellent, tend to be just inside the window, and this is consistent with the tests I saw from Japan.

For me, it is fair to say that they are a half step behind. They are still a premium telescope, and still usually fall in the excellent category but not quite to the level of the TMBs.

So to me, that is a half step behind. A full step lower in quality (in my own ranking) would be in the "Very Good" range, which is the .93 to .94 Strehl range.

I use this ranking because it is the same that Royce uses on his web page. He consideres .95 and above to be excellent, and my own experience easily agrees.

And I was clear to say that I did not think anyone could see the difference between .95 and .98 at the eyepiece on an in focus image. Both will give a view that is identical.

Out of focus, a zone will show though, and if you paid top dollar for a premium scope, I don't think you should expect to see a central zone. And yet I have seen several Televue scopes with such a zone.

These are called "Cosmetic" (and I agree) because when they are at the center of the field, they do very little damage.

But if I bought a new BMW and it had a dull spot on the paint, I would not be happy about it. And if I spent money for a "Premium" scope and saw a zone in the star test, I would be just about as unhappy about that as a cosmetic flaw in the paint of a new BMW.

I like Televue scopes. I have owned 3 and all gave excellent performance.

So, I did not make this news (the Strehl results linked above).. I only reported it.

#18 Eddgie

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Posted 14 February 2013 - 10:25 AM

And as to the relevance to my posts and the data provided, here is what the OP wanted to know:

What I'm curious about are the optics .... mostly the quality of the optics.



I to have no desire to debate the issue regarding Televue's Premium provider status. I believe they sell premium telescopes.

And this for me is in fact a small exercise in splitting hairs.

But the OP asked and the question has been answered using objective test data.

The danger though is that Rorh has only testes a tiny fraction of all the scopes Telvue has ever produced (though he has tested many TMB scopes).

I have to concede that the sample size is to small to be definitive.

On the other hand, a .929 Strhel is nothing special. Rohr has testes a lot of Celestron SCTs that have had better Strehl that .929.

And if the OP bought a Televue scope and star tested it and saw a central zone, how do you think he would feel? Even if the zone was only cosmetic, would he still feel like he made the best decision regarding optical quality????

#19 LivingNDixie

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Posted 14 February 2013 - 10:29 AM

I have used a TV85 quite a bit. It is a nice scope. I have no experience with the other two.

Another scope you don't mention is the FS78. It is a nice scope but pretty heavy for the size it is.

#20 la200o

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Posted 14 February 2013 - 11:27 AM

Aren't most of those bench tests of Genesis models? Long out of production. And any conclusions based on one test (which I think was the case with the 102) doesn't greatly impress me.

And I guess I should not be lazy and look back and find that thread posted by the fellow who thought he might have a zone . . . I seem to recall there was some question whether or not that was really the problem.

Glad you like TV scopes, though. So do I! I never fail to be impressed by mine on the all-too-rare occasions I get to use them. Wonderful instruments, especially when combined with TV's equally "premium" ep's.

Clear skies to you,
Bill

p.s Ed, didn't you write a rave review of the TV101 (not NP 101) on that other site? "4 inch APO's don't get any better than this"? If so, all is forgiven. :jump:

#21 spencerj

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Posted 14 February 2013 - 11:41 AM

I have to concede that the sample size is to small to be definitive.

On the other hand, a .929 Strhel is nothing special. Rohr has testes a lot of Celestron SCTs that have had better Strehl that .929.

And if the OP bought a Televue scope and star tested it and saw a central zone, how do you think he would feel? Even if the zone was only cosmetic, would he still feel like he made the best decision regarding optical quality????


Eddgie, two of your samples were Televue Genesis scopes. That is not just a small sample. That is a barely relevant sample. Those were manufactured in what the late 1980's and early 1990's? 20 to 25 years ago? Maybe you really feel those scopes have anything at all to do with scopes currently manufactured by Televue, but to me that seems a stretch. So Synta and other manufactures have gotten better over the years, but Televue optical fabrication and quality is stuck in the 1980's?

Sure I would like a 120mm Skywatcher with a .979 Strehl, but I am not lucky enough in general to land one of those mythical creatures. I would be more likely to catch a unicorn in the large hole I dug in my backyard.

I bought my TV102 a few years ago before the explosion of 4" Apos. For me it was a safe purchase. I knew that I was going to get the quality scope that I paid for. Best of the Best? No, but dependable quality that I could afford. Today . . . I think I would lean towards a Stellarvue scope, but not because I was afraid of the optical quality of a Televue scope.

#22 Lane

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Posted 14 February 2013 - 04:07 PM

I would suggest the TMB92L instead of the TMB92SS, it is smaller and lighter. The only reason for the SS would be for photography or binoviewing and as most people will tell you, you don't want to binoview with a scope this small. The 92L comes with a nice case that can reworked with new foam to hold everything you need except the mount of course and it will work well on a very simple mount. So a great portable setup for traveling

In regard to the other argument going on here, I have an 80mm and personally I see the 92mm as a big jump. I am not sure I can see anything in the 92 that the 80 can't also see, but it pulls out more detail. Things that look noticeably better to me are Mars, Jupiter, Saturn, most Globular clusters, and many nebula. I see only a slight improvement in double star viewing and open cluster viewing. I think jumping to something in the 105mm to 110mm range is better, but not nearly as portable.

#23 Rossmon

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Posted 14 February 2013 - 05:24 PM

I would suggest the carbon fibre model of the WO FLT98. It is light weight and gets you up to the 100mm aperture. They are gorgeous too. Mine gave me as much pleasure looking at as looking thru! I only sold it to move up to my NP127. I have been extremely pleased with my 127 but i am now going to sell it as I moved up to a 6" AP.
For this particular Televue,, at the EP, the views are as good to better than everything else i looked thru from 4"s to 6"s. No it is not as nice as my 155! but it was just as sharp as a 6" f9 AP that I looked through. Of course, these are totally subjective comparisons.

#24 Joe Bergeron

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Posted 14 February 2013 - 07:28 PM

The difference between a 3" and a 4" is the same as that between a 9" and a 12". Really quite noticeable.

#25 NHRob

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Posted 15 February 2013 - 09:54 AM

Rossman,
How were the optics on your FLT98?






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