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Is the Zeiss 150 APQ the best 6 inch ever?

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#1 mike bacanin

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Posted 02 June 2009 - 03:35 PM

Is the zeiss 150mm APQ the best 6 inch refractor ever?
I'm fascinated by the mystique of these refractors.
How would it compare to modern premium scopes like AP 155,TEC 160,TOA 150,TMB 152, and similar?
Any 150 APQ owners out there to comment?

Mike

#2 Darren Drake

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Posted 02 June 2009 - 03:49 PM

They're all so good it would be impossible to say that one is better than all the others. Several years ago Ed Ting put up an Ap 155 against the best Taks of the time and the AP won both times. So for me the AP scopes are the ones that could be considered best although the Tak 150 TOA I recently borrowed gave phenominal immges. For me all these scopes are in the same class and there would never be agreement by any expereinced group on just one scope or line of scopes: except maybe the APs. :grin:

#3 Mike Clemens

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Posted 02 June 2009 - 04:23 PM

I'm betting the TEC160FL is the king of the mountain, but I'm horribly biased by having to live with one of the white-bread TEC EDs.

#4 hapo

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Posted 02 June 2009 - 04:23 PM

I had the chance to startest this year several high end and not so highend refractors: 1 Zeiss APQ 150, 1 AP 160EDF, 1 TEC 140, 1 132mm FLT from WO, 1 Equinox 120 from Synta all of them with my set of ZAO II eps (which are the most neutral eyepieces regarding CA). The Zeiss APQ was the cleanest refractor in CA and had perfect diffraction rings. The AP refractor had slight CA seen easily in the artificial star test as chocholate coloration of the diffraction rings. The TEC had almost the same correction of CA as the Zeiss, but the diffraction rings were not quite perfect. The WO flt 132 was the worst from all of them, much more CA present than in the Equinox 120, the diffraction rings were not simetrical and showed some astigmatism. So, yes, Zeiss APQ's are the best I have seen.

#5 GJJim

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Posted 02 June 2009 - 04:30 PM

The TEC APO160FL is essentially the same design as the venerable APQ with modern glasses. Here are test results for an APQ that show the performance in red light. A test in green would probably show even better strehl numbers.

#6 Alan French

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Posted 02 June 2009 - 05:06 PM

The TEC APO160FL is essentially the same design as the venerable APQ with modern glasses. Here are test results for an APQ that show the performance in red light. A test in green would probably show even better strehl numbers.


Test results in red light are useless for refractive optics.

Clear skies, Alan

#7 GJJim

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Posted 02 June 2009 - 06:32 PM

The TEC APO160FL is essentially the same design as the venerable APQ with modern glasses. Here are test results for an APQ that show the performance in red light. A test in green would probably show even better strehl numbers.


Test results in red light are useless for refractive optics.

Clear skies, Alan


Yeah you're right, what do those slackers at Zeiss know about optics? I'll stick with the real experts here on CN. :rolling:

#8 Alan French

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Posted 02 June 2009 - 06:58 PM

The TEC APO160FL is essentially the same design as the venerable APQ with modern glasses. Here are test results for an APQ that show the performance in red light. A test in green would probably show even better strehl numbers.


Test results in red light are useless for refractive optics.

Clear skies, Alan


Yeah you're right, what do those slackers at Zeiss know about optics? I'll stick with the real experts here on CN. :rolling:


I was overstating things, but the reality is that you want a lens tested in green light. A good test in red probably indicates it does fairly well in green, but there is no way to know if it will test worse or better in green light. With mirrors, you can extrapolate to different wavelengths. With refractive optics you can not.

If Zeiss wants bragging rights, why not test in the wavelength our eyes are most sensitive to?

Clear skies, Alan

#9 suburbanskies

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Posted 02 June 2009 - 07:13 PM

Ah, Mike I knew you'd start thinking about a 6" apo :)

Mark

#10 JumboFlex

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Posted 02 June 2009 - 09:23 PM

I wonder what it is about Zeiss that they manage to create these optical wonder works, I guess they just now what they are doing. I have yet to come across a review of these scopes that doesnt come back with superlatives entrenched in them.

I wonder what Zeiss would charge for these things if they produced a limited run of new scopes?

#11 Alan French

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Posted 02 June 2009 - 09:34 PM

Zeiss did make wonderful scopes, but there are other companies, such as TEC and AP, who are highly skilled and create instruments of fine optical quality.

There was no magic that Zeiss performed that can't be equaled today.

Clear skies, Alan

#12 BillP

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Posted 02 June 2009 - 09:45 PM

And if Zeiss were convinced by someone (hint hint) to also make another run of some scope optics, what should that one aperture be?? 130? 140? 150? 160? If considering some limited run of something, should be managable for the greater public and something not wanting too much from a mount IMO. I'd vote for something like a 145mm. Something bigger than the venerable and popular TEC140, and something to challenge all the 150 class scopes since it is a Zeiss and would be up for the challenge. Plus keeping it under 150mm to save some weight to make mounting managable. But why not two? A 145mm and an 88mm! Nice odd sizes :grin:

#13 JumboFlex

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Posted 02 June 2009 - 09:47 PM

Zeiss did make wonderful scopes, but there are other companies, such as TEC and AP, who are highly skilled and create instruments of fine optical quality.

There was no magic that Zeiss performed that can't be equaled today.

Clear skies, Alan


I agree in that there are some great optics out there, I just find it curious that whenever a Zeiss product is tested against those companies wonderful products the reviewers always seem to give the Zeiss the edge. I can attest to the ZAO II's being top level but have never looked through one of their refractors.

#14 GJJim

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Posted 02 June 2009 - 10:45 PM

I was overstating things, but the reality is that you want a lens tested in green light. A good test in red probably indicates it does fairly well in green, but there is no way to know if it will test worse or better in green light. With mirrors, you can extrapolate to different wavelengths. With refractive optics you can not.

If Zeiss wants bragging rights, why not test in the wavelength our eyes are most sensitive to?

Clear skies, Alan


Back in the day (1998), everyone used red, He-Ne lasers because that is all that was available in interferometers. I'm sure the spherical error is greater in red than green, but the interferogram is still useful as it shows a smooth wavefront and a Strehl ratio better than most lenses achieve at their design wavelength.

#15 GJJim

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Posted 02 June 2009 - 10:52 PM

And if Zeiss were convinced by someone (hint hint) to also make another run of some scope optics, what should that one aperture be?? 130? 140? 150? 160?


The group at Zeiss that did this work was disbanded years ago. If people want a modern equivalent of the APQ design, then a phone call to TEC will get you the goods in either 110, 160, or 180 millimeters of aperture.

#16 ValeryD

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Posted 03 June 2009 - 12:04 AM

The TEC APO160FL is essentially the same design as the venerable APQ with modern glasses. Here are test results for an APQ that show the performance in red light. A test in green would probably show even better strehl numbers.


Test results in red light are useless for refractive optics.

Clear skies, Alan


You are not correct, Alan.

The only cases, where you are correct, are:

Relatively fast Doublets and triplets with small air gap between their lenses and oiled triplets.

There are several designs with corrected spherochromatism and in these case tests in red light are quite usefull.
Note, that APQ design has red and green corrected almost equally.

#17 Mike Clemens

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Posted 03 June 2009 - 12:45 AM

> And if Zeiss were convinced by someone (hint hint) to also
> make another run of some scope optics

It would probably be something like "40 of the six inch refractors will be created, selling for $24,999 each"

#18 Alan French

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Posted 03 June 2009 - 07:33 AM

The TEC APO160FL is essentially the same design as the venerable APQ with modern glasses. Here are test results for an APQ that show the performance in red light. A test in green would probably show even better strehl numbers.


Test results in red light are useless for refractive optics.

Clear skies, Alan


You are not correct, Alan.

The only cases, where you are correct, are:

Relatively fast Doublets and triplets with small air gap between their lenses and oiled triplets.

There are several designs with corrected spherochromatism and in these case tests in red light are quite usefull.
Note, that APQ design has red and green corrected almost equally.


Valery,

Thank you for the correction. So, if we know the design has low spherochromatism, then a test in red light would be close enough to show what the lens looks like in green?

Thanks again.

Clear skies, Alan

#19 Jeff B

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Posted 03 June 2009 - 07:47 AM

I find interesting the tendency to judge the generic quality of an OEM based upon a single sample.

Please notice that each scope from OEMS like AP, TEC, TAK, Zeiss, APM and others has a unique serial number. They are individuals. Each OEM is capable of making excellent scopes but there is variation as they are all hand figured and corrected.

To draw the conclusion that one OEM is better than another based upon comparison testing of one sample from each is folly, IMO.

Jeff

#20 Cotts

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Posted 03 June 2009 - 08:07 AM

Tests where the evaluators know which telescope they are looking through are biased. No matter how honest the viewers try to be their preferences creep through into the 'results'. Real science requires a double-blind test where the viewers and the people who set up the test are not aware of which scope is which. (A non-involved person keeps the actual names secret until the test is over and does not go near the test.) So why don't we set up such a test, perhaps at the WSP next February, with a few 5"-6" f/7-8 refractors covered with paper to hide their identity, a team of experienced 'testers' and an experimental design that is truly double blind. I would be willing to be involved in such an endeavour. Anyone else?

d.c.

#21 hapo

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Posted 03 June 2009 - 09:54 AM

Some things are obvoius if you put the instrument on the test bench, and can be quantified. Even a star test on artificial star can reveal many things easily. So any blind tests are not really necessary.

#22 GJJim

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Posted 03 June 2009 - 09:58 AM

So why don't we set up such a test, perhaps at the WSP next February, with a few 5"-6" f/7-8 refractors covered with paper to hide their identity, a team of experienced 'testers' and an experimental design that is truly double blind.


A meaningful test also requires a meaningful sample size. Setting up a few scopes side by side, double-blind, is interesting yes, but it's no more "scientific" than the many comparison tests and "shoot outs" we've already seen.

#23 EddWen

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Posted 03 June 2009 - 10:16 AM

"....but there is variation as they are all hand figured and corrected...."

If the baseline of the variability is sufficiently high, the manufacturers build a reputation over time of building excellent products, regardless the variability.

Does one ever hear of a 'lemon' TEC, A-P or Zeiss?

#24 Alan French

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Posted 03 June 2009 - 10:23 AM

Given the many variables involved, an objective comparison is difficult. Seeing changes with time, eyepieces get dirty, transparency changes, and so on. Seeing is a tough one. When we've done informal comparisons, it is very easy to keep changing your mind about which instrument does best. Even under WSP skies, there is often some variation in seeing.

I've looked through a lot of high end apochromats over the years, and pretty much decided there is little need to fret over possible differences between the best of the breed, and it is far better to enjoy to night sky with a quality instrument than to spend time doing comparisons.

I sometimes wonder about people who spend time debating the merits of various telescopes. One year such a discussion was going on next to a large apochromat at WSP. Saturn was very high and marvelous, yet these folks were just standing around talking. I enjoyed it - I could wander over and take a long look any time I wanted - but thought is was rather strange.

Clear, steady skies, Alan

#25 Jared

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Posted 03 June 2009 - 01:04 PM

You are spot on, Alan! I recently purchased a used 152mm scope and was worried when my initial star tests didn't look so good. Inside focus was lovely, but outside of focus was seriously degraded--little contrast between the rings and very soft edges.

Spherochromatism?

I tried a green filter with little improvement... Was something wrong? Had I gotten a lemon? Did the manufacturer's test results lie? Were the images I was seeing not as good as I thought they were? Was it time to panic?

I resolved to wait for a night of excellent seeing when the scope had had ample time to cool.

A a couple of weeks later, on an evening of excellent seeing I ran the star test again and got what appeared to me to be perfect results. I'm sure there were some subtle differences, but I stopped worrying. I have vowed that I will do no more star tests on this scope (except perhaps for demonstration purposes to owners of inferior telescopes :lol:). Instead I will concentrate on the intended uses--observing and taking pictures. Taking pictures through the scope, that is, not of the scope.

It seems to be very much a trait of far too many of us that we obsess over the kit rather than enjoying the views. The statement about the best scope in the world being the one you actually use may seem cliche, but it is actually a very important point. We need to stop splitting hairs and spend more time enjoying the views!

All of the scopes mentioned by the original poster are, by reputation, superb. I'm sure they all provide wonderful views. We should concentrate on more important topics--like how much better my 4" refractor is than the other guy's 8" SCT!






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