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Why do really expensive scopes sell and what attracts us to them ?


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2 minutes ago, neil phillips said:

They are expensive i think because it cost more to produce better quality, and here is a big one manufacturers can charge what they like. If people will buy. And they know they will

Not sure if we should be thinking like that.

Telescope can cost as much as a small car - or say sports motorcycle. Can we compare quality of product between the two? Even with all hand crafting - sports motorcycle requires more man/hours of precision labor to be made. Yet they cost the same.

Economies of scale come into play here and standardization. You don't have to hand craft every bolt on motorcycle and so on.

Chinese telescopes for example share components - like finder shoes, or focusers or scope rings and so on - that brings their cost down - but do they suffer poorer quality because of that? Not if QA is good enough. Even with high volumes one can assure satisfactory quality of product.

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2 minutes ago, Franklin said:

OK, we're a bunch of old hippies. Lets get back to scopes.

@vlaiv's question is relevant. I think the Tak will win on 1st point Optical Quality. It is fluorite as opposed to FPL-53. The Tak will be more apochromatic.

How about against FPL-51 or FPL-53 triplet that is less expensive?

I was under impression that Taks are known for their quality of figure rather than absolute color correction?

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12 minutes ago, vlaiv said:

Not sure if we should be thinking like that.

Telescope can cost as much as a small car - or say sports motorcycle. Can we compare quality of product between the two? Even with all hand crafting - sports motorcycle requires more man/hours of precision labor to be made. Yet they cost the same.

Economies of scale come into play here and standardization. You don't have to hand craft every bolt on motorcycle and so on.

Chinese telescopes for example share components - like finder shoes, or focusers or scope rings and so on - that brings their cost down - but do they suffer poorer quality because of that? Not if QA is good enough. Even with high volumes one can assure satisfactory quality of product.

Not sure what i am missing but the points you just made sound exactly like point two. At least your first point does 

manufacturers can charge what they like. If people will buy. And they know they will

Edited by neil phillips
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14 minutes ago, vlaiv said:

known as "but is it x10 better".

No it wont be 10x better IMHO.

A big factor is the cost of the top notch glass ie vg glass these days is reasonable- to get to the levels above this gets costly and I think a lot of lenses get tossed by QA. After counting bubbles and inclusions, testing for polish, figure etc makes might have to go through a few sets of lenses produced to get the best ones for the specs required by some scope makers.

LZOS probably just tosses the sub spec lenses back in the pot to be remelted.

My 90mm SV Raptor has vg glass, Chinese of course. It is an excellent scope and I dont think a Baader 90mm would be so much better that I woudnt use it.

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19 minutes ago, vlaiv said:

- Optical performance

- Mechanical fit&finish

- Value depreciation over time?

- "Lust factor" / "availability" / "status" ?

That about covers the options I think@vlaiv

Number one has to be paramount in my book. Tak focusers definitely aren’t up there with the best, I replaced mine with a Feathertouch without even using it! A scope like this should have a decent dual speed focuser as standard I reckon.

To be honest, with number two many others are at similar levels to premium. I think, and unless in short supply, premium brands don’t always hold their value that much better. Orion Optics certainly don’t, not sure why. Actually it’s probably because apart from the mirrors they are fairly standard, and mirrors need re coating so the value drops away. At least a premium refractor maintains its optical performance if it is kept properly.

So, it’s probably 1 and 4 although it will vary by brand and type.

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APM put the specs they use for their LZOS objectives in the public domain. I guess they were stringent back in 2005 but maybe not so much today ?

APMApo-Linsen-Spezifikationen.pdf

My priority has always been to try and get the best optical quality that I can afford. I've never been too fussy about focusers etc or even the quality of fit and finish, as long as the optical quality is there. With the more expensive scopes I would hope to get better quality in these departments as well.

Although not too fussy about focusers, even I can appreciate that the Feathertouch fitted to my TMB/LZOS 130 is something above and beyond anything else I've used though.

With a triplet refractor I think the mechanical design and precision of the objective cell is very important as well. Another area where the LZOS triplets seem extremely well executed. I'm sure that Tak and Astro Physics have great quality objective cells as well.

tmb3-jpg.202505

 

 

 

 

 

Edited by John
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To be fair - point four I included because I'm aware exists - but it does not really figure in the way I look at things - which pretty much leaves number one as prime candidate.

Herein lies the problem for me.

I understand that there is difference, and I can accept that last few percent of performance come at very steep price.

I just don't really understand how much difference those last few percent really make.

I have to go by very conflicting data sets - we have personal experiences that varies but in general there is consensus - expensive = better and it can be seen at the eyepiece.

On the other hand - theory suggests that you should be able to hardly notice - if at all. I did my simulations, but there are resources available online as well. Here are few sim images produced by Damian Peach:

image.png.8233adcced161169bd3a9ff250ad689a.png

Top is 1/10th wave optics - bottom is "diffraction limited" - or 1/4th of wave optics.

If that is the difference between 1/10th and 1/4th - I wonder if we would be able to see it at all between say 1/8th and 1/6th or perfect and 1/8th.

Now, there are few explanations for this discrepancy:

- observer bias

- theory being wrong

- application of theory outside its domain of validity

I really doubt that theory is wrong, but we could possibly use it outside of domain of validity - maybe it is valid for recorded images but our eyes might see things differently and we did not include this into account.

Then - there could be observer bias. Maybe people simply expect more expensive scopes to perform better?

Maybe it is something completely different - maybe what we think are "average/good" samples are in fact poor samples and therefore very different than "excellent" samples?

All of this is something that I would like to understand more before "deciding" if expensive is worth it. To me - if difference is there - then yes, some will have the money and be prepared to buy the best possible - and that is a good thing as those that produce the best will be kept in business and everyone will have a choice.

But if difference is not there - how to justify it?

 

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3 minutes ago, John said:

APM put the specs they use for their LZOS objectives in the public domain. I guess they were stringent back in 2005 but maybe not so much today ?

That is really interesting - they quote peak-to-valley error of no more than 0.24 (for scopes up to 150mm of aperture) - that is just a tiny fraction better than 0.25 or 1/4th of wave P2V.

What they are really saying - our scopes are "diffraction limited" :D or have Strehl of higher than 0.8.

Maybe we are being mislead by low cost scopes that advertise as "diffraction limited" - maybe they are much poorer than that?

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I think there's a question of style and influence. When I look at the modern telescope market I really see only two veins of influence on telescope styles. There are scopes whose style is heavily influenced by the Japanese telescope makers eg, fixed dew shields, single speed r&p focusers and great optics ( Takahashi, Pentax and Vixen ) and then there is a plethora of different branded scopes ( which all probably come from Long Perng ) which to my eye seem to take their style influence from US, European and Russian telescope makers. Their dual-speed black anodised focusers, retractable dewshields and great optics remind me of Astro-Physics, APM Lzos and Tec style scopes.

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4 minutes ago, vlaiv said:

That is really interesting - they quote peak-to-valley error of no more than 0.24 (for scopes up to 150mm of aperture) - that is just a tiny fraction better than 0.25 or 1/4th of wave P2V.

What they are really saying - our scopes are "diffraction limited" :D or have Strehl of higher than 0.8.

Maybe we are being mislead by low cost scopes that advertise as "diffraction limited" - maybe they are much poorer than that?

I believe that all LZOS objectives are guaranteed to have a strehl of 0.95 or better ?

 

 

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6 minutes ago, vlaiv said:

That is really interesting - they quote peak-to-valley error of no more than 0.24 (for scopes up to 150mm of aperture) - that is just a tiny fraction better than 0.25 or 1/4th of wave P2V.

What they are really saying - our scopes are "diffraction limited" :D or have Strehl of higher than 0.8.

Maybe we are being mislead by low cost scopes that advertise as "diffraction limited" - maybe they are much poorer than that?

Which reminds me of Orion optics testing a skywatcher mirror, And claiming it was actually pretty good. So either they lied. There testing is wrong or inadequate. Or actually we are not being lied to, there testing is not inadequate  and the point i originally made has some validity ? 

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9 minutes ago, John said:

I believe that all LZOS objectives are guaranteed to have a strehl of 0.95 or better ?

 

 

image.png.64ae697c92fb94c675d14cb9fd6fd005.png

Or translated to other values:

image.png.bfc774d93eff01746a09c3a4c9dbb76f.png

image.png.4da289a046b2242cba56fedb09954420.png

Interestingly their RMS is much lower than these calculation suggest.

Not sure if that is possible. Above calculator probably only calculates spherical aberration and not general aberrations, but I think that spherical is rather smooth variation of wavefront and thus RMS should be small for given P2V (RMS is measure of how much on average wavefront deviates from perfect, while P2V is just two most distinct points - but if we account for "smooth" transition between two most distinct points of error - we should get rather small RMS).

 

7 minutes ago, neil phillips said:

Which reminds me of Orion optics testing a skywatcher mirror, And claiming it was actually pretty good. So either they lied. There testing is wrong or inadequate. Or actually we are not being lied to, there testing is not inadequate  and the point i originally made has some validity ? 

That is actually very good point - can we trust telescope test results and to which extent?

I was really pleased to find out about Roddier analysis. Idea seemed sound and I did some testing on my scopes - and got very good results. Whole concept of DIY testing is very pleasing - you don't have to take anyone's word for it - just do it yourself. Problem is however that it is not reliable. When I created synthetic images that should be very easy to "solve" and calculate wavefront errors (like as simple as pure 1/4th spherical) - it gave wrong results. If it can't produce accurate results in ideal conditions - how on earth will it work with actual data that has noise in it and is far from perfect.

 

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1 minute ago, vlaiv said:

image.png.64ae697c92fb94c675d14cb9fd6fd005.png

Or translated to other values:

image.png.bfc774d93eff01746a09c3a4c9dbb76f.png

image.png.4da289a046b2242cba56fedb09954420.png

Interestingly their RMS is much lower than these calculation suggest.

Not sure if that is possible. Above calculator probably only calculates spherical aberration and not general aberrations, but I think that spherical is rather smooth variation of wavefront and thus RMS should be small for given P2V (RMS is measure of how much on average wavefront deviates from perfect, while P2V is just two most distinct points - but if we account for "smooth" transition between two most distinct points of error - we should get rather small RMS).

 

That is actually very good point - can we trust telescope test results and to which extent?

I was really pleased to find out about Roddier analysis. Idea seemed sound and I did some testing on my scopes - and got very good results. Whole concept of DIY testing is very pleasing - you don't have to take anyone's word for it - just do it yourself. Problem is however that it is not reliable. When I created synthetic images that should be very easy to "solve" and calculate wavefront errors (like as simple as pure 1/4th spherical) - it gave wrong results. If it can't produce accurate results in ideal conditions - how on earth will it work with actual data that has noise in it and is far from perfect.

 

There was a testing facility in Europe ( russian if i remember ) where they tested almost all known brands commercially available. The results were very interesting. Not sure if anyone has that link. But its quite informative 

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2 minutes ago, neil phillips said:

There was a testing facility in Europe ( russian if i remember ) where they tested almost all known brands commercially available. The results were very interesting. Not sure if anyone has that link. But its quite informative 

That one is for bookmarks surely :D

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5 minutes ago, vlaiv said:

image.png.64ae697c92fb94c675d14cb9fd6fd005.png

Or translated to other values:

image.png.bfc774d93eff01746a09c3a4c9dbb76f.png

image.png.4da289a046b2242cba56fedb09954420.png

Interestingly their RMS is much lower than these calculation suggest.

Not sure if that is possible. Above calculator probably only calculates spherical aberration and not general aberrations, but I think that spherical is rather smooth variation of wavefront and thus RMS should be small for given P2V (RMS is measure of how much on average wavefront deviates from perfect, while P2V is just two most distinct points - but if we account for "smooth" transition between two most distinct points of error - we should get rather small RMS).

 

That is actually very good point - can we trust telescope test results and to which extent?

I was really pleased to find out about Roddier analysis. Idea seemed sound and I did some testing on my scopes - and got very good results. Whole concept of DIY testing is very pleasing - you don't have to take anyone's word for it - just do it yourself. Problem is however that it is not reliable. When I created synthetic images that should be very easy to "solve" and calculate wavefront errors (like as simple as pure 1/4th spherical) - it gave wrong results. If it can't produce accurate results in ideal conditions - how on earth will it work with actual data that has noise in it and is far from perfect.

 

Which really begs the question. what is the most reliable form of optics testing

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1 minute ago, neil phillips said:

There was a testing facility in Europe ( russian if i remember ) where they tested almost all known brands commercially available. The results were very interesting. Not sure if anyone has that link. But its quite informative 

There was a German forum called astro-foren or similar that published tests by a Herr Rohr. There are some in this blog:

http://interferometrie.blogspot.com/

This describes his method but it is in German:

http://r2.astro-foren.com/index.php/de/

I'm out of my depth when it comes to detailed discussion of optical testing and results to be honest. Respect to those who know what they are talking about in this area :icon_salut:

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9 minutes ago, neil phillips said:

Which really begs the question. what is the most reliable form of optics testing

I know very little about common methods of testing, but I do have few ideas of how it can be done. One of those is rather easy to do (in principle).

"Simple" in house strehl measurement. This one can't really test telescope by itself. It needs some sort of optical aid - either a barlow or eyepiece.

I think good sharp ortho is better option.

It is very similar to what I've described above - it involves taking an image thru the eyepiece, but this time instead of using an object (image of planet or a nut :D ) - one would image artificial or real star (artificial placed far enough is probably better choice).

Image is taken and then circle that represents airy disk is selected on the image - pixel values in circle and outside of it are summed and ratio is found in_pixels / (out_pixels+in_pixels) - that is Strehl ratio or "encircled" energy (or photon count in this case).

Another method would produce actual wavefront - but it is much more complex and requires specialist software to be written. It works on the principle that I though Roddier works - but now I'm not so sure of that (I haven't read Roddier's paper). It would involve taking several defocused star images and then running software that "solves" what sort of wavefront would produce those kind of out of focus patterns.

 

Edited by vlaiv
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Me neither i will leave that question to the experts. Suffice to say i always thought interferometer testing was the gold standard. Though even temperature differences can affect its reliability. Which again i believe is averaged out. Those with in depth knowledge should continue this side to the discussion. Out of my depth unfortunately But its a question related to points you made

Edited by neil phillips
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52 minutes ago, vlaiv said:

To be fair - point four I included because I'm aware exists - but it does not really figure in the way I look at things - which pretty much leaves number one as prime candidate.

Herein lies the problem for me.

I understand that there is difference, and I can accept that last few percent of performance come at very steep price.

I just don't really understand how much difference those last few percent really make.

I have to go by very conflicting data sets - we have personal experiences that varies but in general there is consensus - expensive = better and it can be seen at the eyepiece.

On the other hand - theory suggests that you should be able to hardly notice - if at all. I did my simulations, but there are resources available online as well. Here are few sim images produced by Damian Peach:

image.png.8233adcced161169bd3a9ff250ad689a.png

Top is 1/10th wave optics - bottom is "diffraction limited" - or 1/4th of wave optics.

If that is the difference between 1/10th and 1/4th - I wonder if we would be able to see it at all between say 1/8th and 1/6th or perfect and 1/8th.

Now, there are few explanations for this discrepancy:

- observer bias

- theory being wrong

- application of theory outside its domain of validity

I really doubt that theory is wrong, but we could possibly use it outside of domain of validity - maybe it is valid for recorded images but our eyes might see things differently and we did not include this into account.

Then - there could be observer bias. Maybe people simply expect more expensive scopes to perform better?

Maybe it is something completely different - maybe what we think are "average/good" samples are in fact poor samples and therefore very different than "excellent" samples?

All of this is something that I would like to understand more before "deciding" if expensive is worth it. To me - if difference is there - then yes, some will have the money and be prepared to buy the best possible - and that is a good thing as those that produce the best will be kept in business and everyone will have a choice.

But if difference is not there - how to justify it?

 

I can only refer you to my first post on the thread @vlaiv, comparing a good fpl-53 triplet with the FC100DC. I’ve had over 50 scopes, some more expensive and have no reason to be biased towards the Tak over anything else. The Tak has stayed for a reason. Optically it’s no better than the Vixen FL102S but it terms of size and portability it’s much more useable. It doesn’t defy the laws of physics, and as I’ve said aperture can still win in certain areas even when in an entry level scope like the 150p. Planets are certainly better in my 8” f8 than the Tak when the conditions are right, but if I’m using the Tak because it cuts through the seeing better, or was easier to put out, or came away to a dark site with me on holiday because it fitted then it’s the better scope at that time. The Tak is about high performance in a small package for me.

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Not sure if my point has already been made as I am only halfway through this very interested thread,  but could psychology be a part of our expectations ? It has been a very grey area and one that is impossible to prove but sometimes our expectations can be ruled by the positive hype and reputation to such an extent that we are  not willing  to accept that the difference is only marginally better than we expected.

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