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My Review of Zambuto 10" Mirror for XT10i

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#176 City Kid

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Posted 06 July 2011 - 07:55 PM

I am buying the mirror.


Congratulations. I hope you will keep us up to date on the testing of your secondary as well. I decided against having my secondary tested because I've pretty much made up my mind I'm replacing it anyway. I'm going with a smaller secondary.

#177 NickG

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Posted 06 July 2011 - 07:55 PM

I didn't spot this: were all observers aware which scope contained which mirror or did some observers test the scopes blind?

I had no knowledge of whos scope was whos when I arrived, but I quickly inferred the answer through casual conversation and seeing how the scopes were being handled by Sean and David. So the blind test was possible, but it would have been difficult to keep it blind for long.

I will say this though, the difference was obvious. One look at M13 through each scope utilizing the pair of 10mm Pentax EPs would end the blind testing.

All this talk from others about quality the views being "subjective" seems to miss the fact that telescopes are tools for performing a job. Its not like a chocolate vs. vanilla subjective choice, where neither is nessecarily preferred over the other. We can all agree that scopes are designed to help us see faint distant objects, its not subjective to say that one scope performs that task better than another. Unless of course someone prefers lower contrast, lower detail, washed out views over crisp easily defined views. But thats crazy. The tool has a purpose that we all can agree on, and thats not it.

Subjective evaluations are more pervasive when talking about price vs. performance.


Well said Jason.

Funny how all too often we can't trust our amazing abilities to perceive things. (well, some people!) :grin:

I really enjoyed reading the reports. It would have been a really fun night comparing and looking looking at those objects. Also be interesting to hear more about the possible effect of pinched optics (if that was the problem) in the stock scope. Enjoy your new mirror!

Clear skies

#178 David Pavlich

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Posted 06 July 2011 - 08:46 PM

Hey Dave...you guys did a great job! Very good information dispensed and it should leave no doubt as to why many pay the premium dollar for a premium mirrored Newt. :bow:

David

#179 Bowmoreman

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Posted 06 July 2011 - 08:59 PM

Congrats to all on performing this test and reporting.....

Let me toss one more suggestion out on flocking your xt10. As I recall this scope and typical of many today, the tube was too short. Rack your focuser all the way in and look through the empty focuser on an upward angle. You probably will see "daylight" when you flock your scope etend the flocking past the end of the tube about 4 inches. It will address this issue. The other scope has a focus 3/4 inch out, and this would largely address this issue.

Other suggestion is that if you remember the direction of the pinch in the optics, you can rotate your primary 90 degrees when you adjust your clips, if the pinch is still apparent, and 1 if it didn't move it's the secondary, my bet, or it's a primary figure issue.....

As a curiosity was the veil visible without the o3?

Last question are you buying a zoc?

Again thanks to all.......


I just do jot think the flocking was the delta, it really was dark... I have basically NO local LP... so nothing to reflect...

yeah, I think I am buying the mirror... not cheap, but how does one go back?

#180 Bowmoreman

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Posted 06 July 2011 - 09:02 PM

veil was only with OIII

#181 Bowmoreman

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Posted 06 July 2011 - 09:11 PM

the veil is invisible without the OIII. i WANT a zoc mirror, but im happy with sending my primary out for free testing @ owl. and possible refiguring to more than 1/4 wave, and save some money and get a 13 ethos :p or the 31t5 my new dream EP. thanks dave :p what i plan on doing is after flocking take some extra material and do what you said ill make a dew shield extending over the ota.

btw dave did you get a chance to do the azimuth fix? if and when you do your scope will be one awesome piece of optical equipment.

clear skies! ! !

btw definatly my optics were pinched, i loosened all the hold down tabs on the primary which were tight. when i take my setup on my dark sky vaca next week ill report if it fixed it or not.


you and Jason are most welcome, we should do it again... maybe check out Steve's M300...

have not done the az fix yet...between work and a busy day modding CN... no time, and now am really tired....

Last night above all was FUN... been quite a while since I have done that much visual, missed it... AP may be fun and challenging, but it is lonely...

was pleased to share the 31T5, Ethoses and Paracorr, hope it wasn't too corrupting... ;)

Lordy I am tired today though! :smarty:

#182 UmaDog

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Posted 06 July 2011 - 09:22 PM

Thanks for the reply, Jason. It seems the difference was significant indeed.

I think the word "subjective" isn't being used in the way you think (speaking for myself at least, I wasn't thinking simply of "chocolate/vanilla"). In this instance, subjective means (to me) the inability to, say, plot a graph or take a picture which would allow others to objectively assess what I did or saw. There's obviously nothing wrong with opinions formed without graphs, but it can sometimes make it harder for others to make an assessment if only a verbal report is available to them. This form subjectivity was, of course, responsible for the naysayers earlier in this thread.

I should note that I am convinced by the detailed and careful observing reports that you guys have taken the time to make. Thanks again for those.

#183 idealistic

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Posted 06 July 2011 - 09:46 PM

Youre welcome, and my comment on the objective vs. subjective comment wasnt directed at you at all, simply an afterthought. Ive read your posts in the past and think that we tend to have the same thoughts on many topics.



#184 billyo

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Posted 07 July 2011 - 12:54 AM

Those are great questions. The answers would add a bit of data to an essentially qualitative report. However,I'm afraid any answers will be by biased by all the talking taking place between observers. Maybe I'm wrong but lots of talk hurts the needed objectivity in this experiment.

#185 David Pavlich

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Posted 07 July 2011 - 05:18 AM

Those are great questions. The answers would add a bit of data to an essentially qualitative report. However,I'm afraid any answers will be by biased by all the talking taking place between observers. Maybe I'm wrong but lots of talk hurts the needed objectivity in this experiment.


By its very nature, a side by side comparison using differing sets of eyes will bring subjectivity into the mix. I can't be helped. What these guys did was arrange a comparison on the fly. The results are what they are. Nobody said it was a scientific study.

David

#186 Bowmoreman

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Posted 07 July 2011 - 05:48 AM

Yep. Totally on the fly and spontaneous.

I got the mirror at my turn in the rotation...

and then invited anyone local who had a desire to come.

I (we) never had any intention of a rigourous, scientific, double blind with control experiment.

it was always about the viewing.

my final install, hopefully, will be at/after camping at a darker site this weekend, skies willing.

#187 Moey

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Posted 07 July 2011 - 08:09 AM

I've been reading this thread with very keen interest and like to share some brief comments.

I've owned 4 dobs now, 3 of them gso's and 1 of them was a portaball 8" with a zambuto mirror. I must admit before purchase the portaball, I was extremely skeptical about the contrast claims many people made on the web and was happy if it provided same views as the gso as I mainly wanted the scope for the mechanics of the portaball (which I regret selling). The first night I took the scope out, it was obviously from first light that this was no exaggeration, the Zambuto mirror really did provide a more aesthetically pleasing image thanks to the improvements in contrast. There was no doubt and this was confirmed not just by me but other club members of mine.

Now I don't know if this is exclusive to Zambuto or not as I haven't looked through other premium mirrors, and neither do I know whether it is due to the portaball's baffling or not. What was obvious was that after looking through the 8" zambuto mirror, I'd much prefer the views through that scope than my 10" skywatcher having a brighter image. The portaball had a refractor-like image to it, especially when looking at the moon.

I consider myself having a good eye for these things as I'm an avid photographer and pay close attention to the little details many people overlook.So I'm not surprised at people's reports here.

#188 Alan French

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Posted 07 July 2011 - 09:29 AM

I enjoy comparisons, but, as I've said before, there should very detailed descriptions of what can be seen in each telescope. An example here is M27. There are a number of stars embedded in the nebulosity, and a count of these can point to differences. There is also fainter nebulosity outside the apple core, and some detail within the nebulosity. A description of the extent and variation in the nebulosity is very helpful.

Almost any telescope will resolve the double double, the question is in the details. Is there lots of dark sky between the pairs?

Clear skies, Alan


#189 Jon Isaacs

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Posted 08 July 2011 - 10:42 AM

Almost any telescope will resolve the double double, the question is in the details.



Tighter of the two pairs is 2.3 arc-seconds, the Dawes limit for a 60mm is 1.93 arc-seconds, the double-double is doable in a good 60mm. For a 10 inch, it's about seeing and thermal equilibrium...

Jon

#190 Paul R.

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Posted 09 July 2011 - 01:44 PM

Good report...

By the verbal description it sounds as if you experienced (cleaning splitting Polaris, resolved Wild Duck, CE in M-57, superb contrast, etc.) is what I ROUTINELY have experienced for over twenty years through 3 of my telescopes. Nothing out of the ordinary mind you, and I must say it really has nothing to do with the Zambuto mirror as much as with with optics that were fabricated correctly in first place: a discipline that was established over a century ago. The stock optics in your Orion must have been total garbage.

Enjoy! :jump:

#191 jpcannavo

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Posted 10 July 2011 - 06:32 PM

Bluntly put, they are biased.
.......
Tests of this sort would be unpublishable in any reputable scientific or
technical journal.


I have followed this thread with much interest, and I think there is some confusion about the kind of “report” that is being provided here. The above comment illustrates this. The reality is that reports such as these ARE frequently published.

If I may provide an analogy to my own professional work: In medicine we distinguish between formal scientific studies and so-called “case reports”. The former are attempts to establish a firm - and generalizable – conclusion, and are characterized by highly formalized methodology and analysis (i.e. design, blinding, controls, statistics etc). They are therefore subject to similarly formal – and often harsh - criticism.

Case reports, however, do not attempt to draw any general conclusion. They are instead isolated, honest, empirical observations of a particular clinical outcome. Data points, if you will. So, for example, if in switching from drug X to Drug Y, a particular outcome is noted by a physician - that might be published as a case report. The physician making the report, however, makes no claim that in future situations Drug X and Y will behave in similar ways. Consequently, the kinds of formal criticism that would be appropriate for a controlled study would be entirely misguided and irrelevant if leveled against a case report.

The utility of such case reporting is only realized over time. So, if dozens or hundreds, of Drug X & Y reports consistently report similar outcomes, then a later investigator might review the literature, collectively examine these case reports, and now see if some general conclusion can be reached about drug X and Y. Perhaps she/he might choose to do a formal study.

The kind of observing report we have here is much like a case report. Consequently, the most important issue is the sincerity/honesty of those reporting – which is clearly not in question. And so, if the project continues and we accumulate more and more mirror X vs mirror Y repots, the collective of these may suggest a general conclusion, even if no one of them could in isolation. And isn’t this really the way much (but not all) of our “held” amateur astronomy knowledge has come to be - as in “spiral structure typically requires dark skies and large aperture” - by way of a preponderance of isolated, informal observations.

Just my 2 cents

Joe

#192 Roy McCoy

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Posted 10 July 2011 - 07:43 PM

Very nicely put Joe!

Helpful too I believe.

Best Regards,

Roy

#193 dyslexic nam

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Posted 10 July 2011 - 07:57 PM

A bit of epistemolgy on CN - nice.

And agree 100%.

#194 WaterMaster

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Posted 10 July 2011 - 09:16 PM

Great analogy, thanks Joe :bow:

#195 turtle86

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Posted 10 July 2011 - 09:31 PM

Great analogy, thanks Joe :bow:


I agree. This is mainly how, over time, opticians like Zambuto acquire their reputations.

#196 mountain monk

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Posted 10 July 2011 - 10:48 PM

Another plus for you, Joe. Wise.

Dark skies.

mm

#197 TegiriNenashi

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Posted 10 July 2011 - 11:44 PM

Flawed analogy. Even though a drug is just a chemical, they can't do a simpler test than give it to the patient and then observe its effect. Mirror interaction with light is much simpler matter (pun intended). A variety of objective tests exist, and some people on this thread believe these tests are superior to just going to a party, observing complex sky objects there, and drawing conclusions.

#198 NickG

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Posted 10 July 2011 - 11:57 PM

Objective in your mind.

Exactly what is wrong with wanting to share your thoughts on your observations. So we buy optics to sit there and test them with Interferometers? Not saying that isn't interesting though. No one is trying to say that there is anything "mystical" about a quality optic. To the contrary, there must be reasons for the differences, but not everyone is in a position to find out why, in fact, most people aren't.

#199 Wol

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Posted 11 July 2011 - 04:23 AM

"Case reports, however, do not attempt to draw any general conclusion. They are instead isolated, honest, empirical observations of a particular clinical outcome. Data points, if you will. So, for example, if in switching from drug X to Drug Y, a particular outcome is noted by a physician - that might be published as a case report. The physician making the report, however, makes no claim that in future situations Drug X and Y will behave in similar ways. Consequently, the kinds of formal criticism that would be appropriate for a controlled study would be entirely misguided and irrelevant if leveled against a case report."

So apart from interesting bed-time reading along with Tin Tin and Asterix, why publish? Surely an inference is likely to be drawn, albeit a rash one possibly based on a false cause, that outcome Y was because of input X? If the author was suggesting only that Y was a possibility of unknown probability following X, he would have no reason for picking out drug X as opposed to the state of the zodiac at the time.

I'd suggest that it is precisely because of the background assumptions in the relevant discipline that make it not merely an isolated fact within their scientific paradigm, and that is what makes it worthy of note. Precisely because such an outcome was unexpected or contravened known laws that makes it worthy of comment. Perhaps also, the less rigorous the environment and the less any hypothesis is extended to account for it, the less values such a report has.

To get back to this fascinating discussion on mirror quality, I cannot see past the fact that many apparently sincere, knowledgeable, well meaning people disagree even about what it is possible to see never mind what people in fact purport to see.

regards

#200 jpcannavo

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Posted 11 July 2011 - 05:47 AM

"Case reports, however, do not attempt to draw any general conclusion. They are instead isolated, honest, empirical observations of a particular clinical outcome. Data points, if you will. So, for example, if in switching from drug X to Drug Y, a particular outcome is noted by a physician - that might be published as a case report. The physician making the report, however, makes no claim that in future situations Drug X and Y will behave in similar ways. Consequently, the kinds of formal criticism that would be appropriate for a controlled study would be entirely misguided and irrelevant if leveled against a case report."


So apart from interesting bed-time reading along with Tin Tin and Asterix, why publish? Surely an inference is likely to be drawn, albeit a rash one possibly based on a false cause, that outcome Y was because of input X? If the author was suggesting only that Y was a possibility of unknown probability following X, he would have no reason for picking out drug X as opposed to the state of the zodiac at the time.



I have little interest in digressing to far along these lines here. PM me if you want to discuss scientific methodology/epistemology. But in interest of "sound Methodology" you should look at the rest of my post to answere your own question:

"The utility of such case reporting is only realized over time. So, if dozens or hundreds, of Drug X & Y reports consistently report similar outcomes, then a later investigator might review the literature, collectively examine these case reports, and now see if some general conclusion can be reached about drug X and Y. Perhaps she/he might choose to do a formal study.


Let me then just add this much in the way of clarifying my post: An important distinction is between the content of the report issued, and the conclusions – preliminary or otherwise - that might be drawn by the reader. The methodological burden on the reporter is to offer an honest and complete account. The “epistemic burden”, if you will, on the reader is decide when (more similar reports under a range of conditions?), and to what extent, conclusions can be drawn. So of course, point out the range of possible explanations for what was observed. But don’t fall into the category mistake of pointing out the lack of “formal rigor” in such a report.

Joe






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