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AP Mak 10" what the next best thing

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#26 Eddgie

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Posted 11 July 2012 - 08:31 AM

Eddgie, I think amateur/hobbyist testing on Yahoo is not a place to look for consistent test data.).



Rohr uses an optical test bench with an interferometer. That is far from typical amateur equipment.

But believe as you wish. It is pointless to try to reference emperical data on these forums. People seem to prefer to believe other people more than very objective testing. I trust my own star testing and optical bench testing by Rohr far more than most of the postings here on CN. I encourage others to learn to test properly as well. Once you learn to properly perform optical testing, the vail of confusion becomes more transparent.

Rohr is a great tester. Very methodical, and proven to be able to diagonose errors with excellent consistency.

#27 Jon Isaacs

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Posted 11 July 2012 - 09:05 AM

Guy's:

I have no horse in this race. I say this:

Eddgie provided some data from some interferometer testing. Roland would like that. Certainly it is not a sufficient sample to determine the average optical quality of the Takahashi Mewtons but it is real data and for that it deserves respect.

It ought to raise your eyebrows and make you think rather than attack Eddgie for posting it.

Well, I take that back.. I do have a horse in this race, my favorite, the high quality Newtonian... the issue there is the small diffraction limited field of view.

Jon Isaacs

#28 jmiele

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Posted 11 July 2012 - 09:24 AM

Eddgie, I think amateur/hobbyist testing on Yahoo is not a place to look for consistent test data.).



Rohr uses an optical test bench with an interferometer. That is far from typical amateur equipment.

But believe as you wish. It is pointless to try to reference emperical data on these forums. People seem to prefer to believe other people more than very objective testing. I trust my own star testing and optical bench testing by Rohr far more than most of the postings here on CN. I encourage others to learn to test properly as well. Once you learn to properly perform optical testing, the vail of confusion becomes more transparent.

Rohr is a great tester. Very methodical, and proven to be able to diagonose errors with excellent consistency.


All true Eddgie, however not what concerned me. Your blanket statement was my problem. You took exception to everyone else leaving Celestron out of their recommendations as AP Mak alternatives. You didn't like a "blanket omission. You are entitled and it's fine you offered data with it. What was out of line IMO, was your blanket statement concerning Tak and where they rank, IYO, against Celestron.

How much luck do you think I'd have over in the Refractor section saying all scopes other than AP are inferior? It would be inappropriate.


Jon, two people disagreeing with someone making bold statements is not an attack. I've had my nose bloodied several times for overstepping. And tripping. And falling down flat on my face. :) I like Eddgie and he - well, tolerates me. :) But if I sound harsh I can tone it down. I have been slipping on the meds lately. :)

Best, Joe

#29 JohnH

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Posted 11 July 2012 - 09:38 AM

The problem with owning Maksutovs of any sort is that well-made ones spoil you for other instruments. My downfall was a 4" by Quantum years ago.

If you are the handy sort, you could try building yourself one. I have a number of corrector blanks (4 x 4 1/2", 8", 10 3/4" and an 11 1/4" plus a few finished but unmounted correctors. I did get a look at the one built by the late AAVSO member Howard Louth of Sedro-Wooley and was amazed and just a bit humbled by his work.

My 8" Intes Alter m809 (formerly Cotts' m809) is no slacker when it comes to putting up great views. It weighs only 22 lbs and cools well with the fan assist. Because they are underrated, resale values are much lower than what they should be. I've been thinking of selling it but not sure I want to part with such a fine scope for 3Gs or so.


I too own an early M809 f/10 Ites Micro and can testify to their tremendous optical quality, once cool. When I bought my MN-61 (now sold to camvan), this one got a lot less use.

I replaced it with a 7" Intes Mak/Newt that has a cooling fan inside that draws in cool air at the bottom and pushed it out through the holes in the sides of the corrector cell.

BTW, I would be interested in seeing how you cooling set up works. I guess yours must just pull air in and out through the optical port.

#30 RAKing

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Posted 11 July 2012 - 09:51 AM

The problem with owning Maksutovs of any sort is that well-made ones spoil you for other instruments.


+1 with this statement! :waytogo:

I have two examples that will probably never leave my possesion. My little TEC 6 can compete with anything in its aperture class and my Russian STF-Mirage 8" f/10 can stand with the best that Intes has to offer.

Both of these scopes put up star images that are pin point sharp across the FOV and crystal clear. I could never get that kind of performance out of any SCT until the Edge series was developed.

Cheers,

Ron

#31 Jon Isaacs

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Posted 11 July 2012 - 09:57 AM

Jon, two people disagreeing with someone making bold statements is not an attack.


It sure looks that way to me. Based on the data, it is not a "Bold statement", it's just a statement. It may be a surprising statement, one that raises your eyebrows but one supported by data. I see data from Eddgie, no data from anyone else.

To my eye, Eddgie's conclusions were not "blanket statements" but rather reasonable conclusions based on the data about specific telescopes. A blanket statement would be a generalization about all TAK scopes...

Eddgie pointed to the tests he found of TAK Mewtons and some tests of C-11s and pointed out that there are C-11's that test better than those particular Mewtons. That ought to make you think...

The way I read it, Eddgie's point was not that a C-11 is a replacement for the A-P MAK but rather he was questioning whether a Mewton ought to be considered as offering nearly the performance of the A-P MAK.

"One good measurement is better than 100 expert opinions."

Jon

#32 Paul G

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Posted 11 July 2012 - 10:39 AM

The way I read it, Eddgie's point was not that a C-11 is a replacement for the A-P MAK but rather he was questioning whether a Mewton ought to be considered as offering nearly the performance of the A-P MAK.

"One good measurement is better than 100 expert opinions."

Jon


+1

#33 jmiele

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Posted 11 July 2012 - 10:42 AM

He offered the 210. The 210 is in another class from the 250 which is an aperture for aperture match. The reason, he didn't have any data that supported his claim using a Mewlon 250. As such, a bold statement to make. And one made with ZERO personal experience with the instruments in question. The Mewlons 250 or 300 that is. He once again draws his conclusion based on data he reads. This issue has been raised before.

To your one good measurement statement I say this. I've taken 1000's with 100's of instruments. That doesn't mean I'm right.. It comes down to many observations by many testers. The proof is in the market. People don't pay more for an AP because it ISN'T better. They do so because it IS better.

We can continue Jon but I've no intention of conceding the point. I accept yours however.

Best, Joe

#34 Eddgie

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Posted 11 July 2012 - 11:13 AM

The way I read it, Eddgie's point was not that a C-11 is a replacement for the A-P MAK but rather he was questioning whether a Mewton ought to be considered as offering nearly the performance of the A-P MAK.


Thank you.. Yes, this is pretty much exactly what I was saying.

The fact that I used the 210 is simply because I have not seen a test of the 250.

Still, both are Mewlons, and it is to me reasonable to assume that Mewlons are not made to the exact same high qualiity standards of these other scopes. To see so many tests of one type Mewlon that were not above the .95 Strehl threshold makes one question if the quality of the Mewlon product range is not to the same standards as the refractors.

And still, there is the issue of the much larger central obstruction of the Mewlon along with the four vane spider. These are going to lower the contrast so that it is on the oder of a 31% obstruction.

These factors, as your rightly surmize, caused me to question whether the instrument was in the same class as the AP, INTES Micro, or TEC f/15 scopes, which almost always test at the upper limits of optical perfection, and when f/15, have much smaller central obtructions and no spider.

And I still make my strongest recommenation that the most reasonable alternative to an AP 10" MCT would be a Zambuto 10" f/6 mirror with an optimized (17%) secondary.

For a third of the price, someone could put together a scope like this that would deliever essentially the same on axis performance. You would sacrifice the wide field capablitly of an f/6 telescope, but if you wanted to match the f/15 MCT (which itself is a narrow field instrument) then this is a very practical compromise.

The OP wanted alternatives, and this one is not only the most cost effective, it is esentially equal in performance to the MCT.

None of these other scopes would match th e10" f/6 with optimized (17%) secondary. Of the scopes mentioned, this is the only one that will be essentially on par with the AP 10".

But that doesn't really matter if the only thing the OP wants is a big MCT. If a big MCT is his heart's desire, the rest really doesn't matter at all.

If it were a 7" APO that the OP wanted, we could offer wide variety of telescopes that would outperform it on-axis, but that would not matter either.

If one has a desire for a specific type, all the talk here is wasted.

But the OP asked for alternatives, nd I offerend the Intes Micro MCTs (at $10,000 euros) and the far more cost effective 10" f/6 optomized Newtonian.

The bottom line here is that these MCTs have limited demand, and as such, are priced at an extreme premium price.

The OP doesn't want to pay that price, and he doesn't have to pay that price if all he wants is to dublicate the performance. But he won't do that without some compromise elsewhere.

#35 jmiele

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Posted 11 July 2012 - 11:24 AM

For you to make a claim the the Mewlon is not is the same class as the INTES, Tec, et al - Is ridicules! I might even be upset if I thought you'd even looked through even one of them. RIDICULES - There, now you've gone and got me emotional. :)

Eddgie you continue to make your unsubstantiated claims and I'll continue to point them out.

The one thing I will agree with is that scopes in this class and cost have limited appeal these days. They are purpose built and expensive per inch of aperture. They cool slow as well.. But in the end, the views are unparalleled.

Joe <--watching :)

#36 jmiele

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Posted 11 July 2012 - 11:26 AM

"Still, both are Mewlons, and it is to me reasonable to assume that Mewlons are not made to the exact same high qualiity standards of these other scopes."

That's the line that kills me Eddgie.. Your not gonna be getting a christmas card from Art that way! :)


Please, show of hands if you find this utterly ridicules.... Oh, and if you own or have looked through one.

Joe

#37 SandyHouTex

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Posted 11 July 2012 - 12:39 PM

I'm afraid I have to agree with Eddgie. Rohr is recognized as someone who really knows what he's doing and frankly he is the only one I'm aware of that actually tests these scopes in a non-biased way. Yes the sample size is small, but until manufacturers start providing individual test reports with their telescopes, it's the best we have. That and knowledgeable amateurs providing first hand observing reports.

And just for the record I have read about Zeiss, AP, and Tak making a couple of "stinkers".

#38 Erik Bakker

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Posted 11 July 2012 - 01:17 PM

Joe,

I observed Jupiter for only a few hours through a Mewlon 300, so I hope I qualify.

It put up a superfine image of Jupiter, with a level of authority seldom seen. Way above any commercial SCT or Mak. Right there in the Questar 7 territory, just 12" of it . Now I know, some people question the Q7's optics too :lol:

#39 jmiele

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Posted 11 July 2012 - 03:01 PM

Rodger, I wasn't questioning the testing, but the fact that a couple tests don't make a case. And I agree, all companies have had an issue from time to time. How they respond to them is also an important factor.

Erik, You indeed qualify, as a Tak fanboy! :) I too have received a great sample in my Mewlon 300. The views are tremendous. Thanks for your input.

Eddgie, The 210 is 3k scope. the 250 a 8K scope and the 300 a 17K scope. The other Mak and AP and INTES you compared are all in the 8-15K range. I don't think your research and data is an Apples to apples comparison. That's about as fair a race as your C-14 against my Mewlon 300. You'd never get out of the blocks. :)

Best, Joe

#40 TG

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Posted 11 July 2012 - 03:34 PM

"Still, both are Mewlons, and it is to me reasonable to assume that Mewlons are not made to the exact same high qualiity standards of these other scopes."

That's the line that kills me Eddgie.. Your not gonna be getting a christmas card from Art that way! :)


Please, show of hands if you find this utterly ridicules.... Oh, and if you own or have looked through one.

Joe


I do find using voting to determine objective truth utterly ridiculous. :p

Eddgie, stop posting numbers. They only confuse people. Try to come up with more of englist-lit level critiques. Actually write a Shakespearean sonnet about the Mewlon (Shall I compare thee to an Intes Mak, etc. etc.)

:lol:

Tanveer.

#41 Mike Harvey

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Posted 11 July 2012 - 04:05 PM

All this test data makes my head hurt!
I have none to offer, but I can relate a 'real-world' experience.
Over the years I have owned a beautiful Takahashi TSC-225, Mewlon 250 (and, since someone mentioned it - a Questar 7).

NEITHER of the Taks offered any noticeable visual improvement over my (current) 10" Meade ACF! Sorry - but that was/is my experience.
In the case of the Questar...it was markedly inferior in almost every respect.

The BEST Mak I've ever encountered was the MAK-NEWT that Roland Christen brought to the Winter Star Party several years ago. I forget if it was 9" or 10"...and it doesn't matter...it was simply incredible!

Just my 2 cents worth.

Mike Harvey

#42 Eddgie

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Posted 11 July 2012 - 04:11 PM

If your Mewlon was a song, what song would it be? :roflmao:

Seriously, there were four Mewlons that were tested in the link I sent, and none of them had a Strehl of over .95.

I said there were "Two" Mewlons, but this meant two different models, and not two individual scopes.. I sent four links for Mewlon tests.

And of course I would expect a 300mm Mewlon to put up a great image. Nowhere ever ever did I say that it would not.

But I would expect any very good 300mm telescope to put up a fantastic image. 300mm is a lot of aperture, and anyone that knows me will very quickly confirm that I am an advocate of aperture as being one of the most important attributes of telescope performance. And even if the Mewlon had optics that were slighly imperfect, I would expect ot to still outperform most smaller scopes, because once again, it is a lot of aperture.

Would it be better than a 300mm MCT? Or better than a 300mm Optimized (small secondary) reflector? I don't know how it could be.

At any rate, if the OP can't afford a 10" AP or Intes Micro, he may not be able to afford a 12" Mewlon.

But 300mm is a lot of aperture and I would expect any well made 300mm telescope to put up an excellent image.

#43 TPMack

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Posted 11 July 2012 - 04:32 PM

I had my Mewlon 300 parked next to a C14 at Black Forest several years back. On Jupiter, there was nothing on Jupiter's orb in the Mewlon that could not be seen in the Celestron; however, saying that, the background sky in the Mewlon was noticeably blacker while the Celestron's was charcoal.

#44 TPMack

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Posted 11 July 2012 - 05:35 PM

Rohr tests optics using a horizontal interferometer. It would be interesting to comapare his results with a vertical interferometer, especially those big and heavy mirrors.

#45 houser23

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Posted 11 July 2012 - 06:12 PM


"Still, both are Mewlons, and it is to me reasonable to assume that Mewlons are not made to the exact same high qualiity standards of these other scopes. To see so many tests of one type Mewlon that were not above the .95 Strehl threshold makes one question if the quality of the Mewlon product range is not to the same standards as the refractors."

I guess I should just take my Mewlon off its mount and throw it in the garbage then. :grin:

#46 bratislav

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Posted 11 July 2012 - 06:26 PM

Why would primary in Mewlon 210 be so "big and heavy"? And do you ever use your telescopes away from zenith ?
BTW, his "horizontal interferometer" did not seem to affect that much some of 20" to 24" mirrors - they still peaked at 0.98+ Strehl ?

Rohr's measurements are what they are - one man's view of the telescope zoo. You can accept them, you can ignore them. But you CANNOT make them disappear !!! If two of the Mewlons he tested were not so great, that is exactly what they are. Too few samples ? Well, you only need to get one of those sub par samples to understand statistics variation and its importance in real life.

I for one am more than happy that he makes all of his results publicly available. He has no bias, no axe to grind, no ads pages to suffer from bad result, and tests all of those scopes in the same way, to the best of his ability.
My hat is off, Mr Rohr !

#47 Alan A.

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Posted 11 July 2012 - 06:30 PM

I have a friend with this scope and had a chance to look through it at Jupiter under super steady skies at the oregon star party - the level of detail in each band was astounding,

This is an interesting question, but its such a unique scope I don't think there is a close second that can do it all. Lets see, the 10 AP Mak-Cass has an aspheric primary made of quartz with the final figuring done by hand by Roland himself, a 23% obstruction only, a lot of research done by Roland on the design/build end to ensure rapid cooling, and comes in a relatively small tube with eyepiece in the back.

One logical list of close seconds would be:

1. TEC 10" f/20 M-C, I don't know if optics are as good or if it cools as well ( Hopefully Vahe can comment)
2. 250 mewlon, but much higher CO, narrower FOV, and some people report very fussy to collimate dead on ( here on CN I have read both sets of comments: "easy as pie" and " a descent into hell"
3. 8-9" APO, poor portability relative to the AP, painfully expensive ( although the AP MC would run ??30k if you could find one now)
4. 10" f/6 Zambuto newt with 20% obstruction - with either standard spider or an optical window for the secondary.

The 4th would be my personal choice of the lot, and oh look at that, I happen to have one :)

#48 Erik Bakker

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Posted 11 July 2012 - 06:32 PM

I guess I should just take my Mewlon off its mount and throw it in the garbage then. :grin:


Just a sec Jeff, I'll get you a bin asap :lol:

#49 TPMack

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Posted 11 July 2012 - 07:03 PM

[quote name="bratislav"]Why would primary in Mewlon 210 be so "big and heavy"? And do you ever use your telescopes away from zenith ?
BTW, his "horizontal interferometer" did not seem to affect that much some of 20" to 24" mirrors - they still peaked at 0.98+ Strehl ?

Rohr's measurements are what they are - one man's view of the telescope zoo. You can accept them, you can ignore them. But you CANNOT make them disappear !!! If two of the Mewlons he tested were not so great, that is exactly what they are. Too few samples ? Well, you only need to get one of those sub par samples to understand statistics variation and its importance in real life.

Here is what Roland says about testing horizontally:

"Another thing to consider: when you test a large mirror in a horizontal
plane, the weight of the mirror at the edge tends to produce astigmatism where
the
weight bears down. It is virtually impossible to test a large mirror in a
vertical configuration. In my case, I built a vertical test cell for my lenses,
so
I don't have this problem. So, the final test report of a large mirror should
be compensated for this induced astigmatism, otherwise it is not a fair test.

Your question is a good one, but as in all things like this, real life is
more complicated than it appears".

Roland Christen

#50 houser23

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Posted 11 July 2012 - 07:19 PM

With all kidding aside, I think it's unfair to brand the Mewlon line as an equal to a mass produced line of telescopes. Sure there are a few examples of mediocre Mewlons out there but I'm sure if we dig deep enough we will find that all the top shelf scope lines have suffered a bad apple or two as well, but I wouldn't automatically say well if two are bad then so are the rest.


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