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Why won't Zambuto make 6" F/8 mirrors? Truth please.

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#1 nicoledoula

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Posted 27 June 2018 - 05:28 PM

"Too hard" to do?  No. Lack of a market/profitability? No. (The very second Zambuto says they're making 6" mirrors is when 6" Dobs become best sellers again.)  Too close in performance to an 8"?  Maybe. A "plot" to help sell $$$ corrected EP's? Maybe. Any friends of Zambuto out there interested in conning him into making a 6" F/8 for me?  I don't want or need an 8" or 10" Dob....



#2 junomike

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Posted 27 June 2018 - 05:32 PM

Not enough profit I presume.

An 8" or 10" sells for far more.


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#3 Codbear

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Posted 27 June 2018 - 05:36 PM

And I'm guessing the demand isn't there either. From what I read, all of Zambuto's time is taken up with bigger mirror orders from the premium dob makers such as Teeter.



#4 Sky Muse

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Posted 27 June 2018 - 05:41 PM

In the end, it all boils down to...

 

https://www.youtube....h?v=I8P80A8vy9I


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#5 TG

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Posted 27 June 2018 - 06:01 PM

I suspect that a 6" takes practically the same time to grind, polish and figure as an 8". Customers would regardless demand a lower price because of the size and nobody would be happy, not the customer and not ZOC.

 

Have you tried talking with Carl? He may be willing to make you a 1-off.

 

Tanveer.


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#6 starcanoe

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Posted 27 June 2018 - 06:02 PM

A plot by the "Illuminati"....ahhhh the irony.

 

I keep toying with the idea of making mirrors and lenses for a living....6 inch f10 mirrors of near perfection and apochromats of high f ratio keep appearing on my radar.

 

Yeah, the market aint big...but I keep wondering if it can at least keep one dedicated and desperate true believer employed....


Edited by starcanoe, 27 June 2018 - 06:03 PM.

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#7 havasman

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Posted 27 June 2018 - 07:17 PM

If you want the truth you should probably ask him. I doubt it's a secret and he's not that hard to reach.


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#8 dgoldb

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Posted 27 June 2018 - 07:19 PM

I have little doubt that you can pay for an 8" and he will make you a 6".  waytogo.gif


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#9 Redbetter

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Posted 27 June 2018 - 07:20 PM

The benefit of a better figured, better polished mirror compared to an average 6" f/8 is likely not going to be particularly noticeable.  6" f/8's are supposed to be one of the easier types to make well, harder to really mess up.  So why would one want to make 6" mirrors (or smaller) when the greatest reward (improved performance for the customer and dollars/hour for the maker) is going to come from larger mirrors?  From what I can tell he doesn't have a lot of slack time that would encourage him to pursue a less profitable and likely less needed market for his services.


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#10 starcanoe

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Posted 27 June 2018 - 07:30 PM

If you want the truth you should probably ask him. I doubt it's a secret and he's not that hard to reach.

 

I torn between "you can't handle the truth" and "the truth is out there"...

 

Yes I probably do watch too much tv and movies....


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#11 MattT

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Posted 27 June 2018 - 07:31 PM

I made a really nice, no-compromises 6" planetary newtonian years ago and was disappointed with its performance. It had a primary that tested out around 1/8 wave, a 1" quartz diagonal and premium spider with 3 thin vanes. It beat 6" Russian mak-casses with their big secondaries, but a good C8 beat it on Jupiter and Mars - and pretty easily. 33% more aperture is a lot.

 

A mount that will carry a 6" f8 properly will also carry an 8" f6, which - even with a small secondary - is a more versatile scope with 33% better resolution and a larger exit pupil at any given magnification.


Edited by MattT, 27 June 2018 - 07:33 PM.

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#12 starcanoe

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Posted 27 June 2018 - 07:33 PM

So why would one want to make 6" mirrors (or smaller) when the greatest reward (improved performance for the customer and dollars/hour for the maker) is going to come from larger mirrors? 

 

Technically speaking larger GOOD optics are always better....but believe it or not for any given person there is a line where X is too big or heavy or whatever....and size X is the limit (expensive refractor lovers have turned such justification into a fine art...).


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#13 Joe1950

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Posted 27 June 2018 - 07:41 PM

You would probably do better buying a GSO 6" f/8, and having one of the several talented optical crafts-persons test, strip and refigure it.

 

That way, the person doing the fine work wouldn't have to take time to do the grinding and polishing - which is done on machine, but still takes time and effort.

 

I bought a 6" f/8 DOB and tested the mirror and had others look at tests I did and the consensus was that the mirror was maybe a hair better than 1/4λ over corrected. But it also had higher order issues like a central hill and a slightly turned up edge.

 

It was refigured by a known talent and is now better than 1/8λ with a smooth textbook figure. And the views of Jupiter confirm this! Having anything better would be indistinguishable. I also replaced the 1/2λ secondary with a 1/18λ from Antares.

 

mirror comp.png

 

Anyway, that's a possible way to go and get a very fine optic at a reasonable cost. And you may get an excellent sample GSO to begin with! 

 

 

 


Edited by Joe1950, 27 June 2018 - 07:46 PM.

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#14 Redbetter

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Posted 27 June 2018 - 08:20 PM

Technically speaking larger GOOD optics are always better....but believe it or not for any given person there is a line where X is too big or heavy or whatever....and size X is the limit (expensive refractor lovers have turned such justification into a fine art...).

But that has zero to do with the optimization function, cost to benefit ratio, or business side of this mirror size.  The same could be said for a ~4" or 3" mirror...with respect to a 6".  Afterall, the 8" f/6 is nearly the same package as the 6" f/8.   The question is whether or not producing a 6" mirror is an efficient use of time for a premium optics maker considering the market.  Unless business nearly dries up and one needs some fill work, I don't see how this would make sense. 


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#15 Pinbout

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Posted 27 June 2018 - 09:09 PM

it is said, he started out making 8in f6 for $75 ea for starmasters...

 

when starting out either you spend a lot of $ marketing upfront...or you charge next to nothing to get people talking about you.

 

it wasn't that long ago he was doing trade-in imports...but also that aint happenin' anymore.


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#16 starcanoe

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Posted 27 June 2018 - 09:36 PM

But that has zero to do with the optimization function, cost to benefit ratio, or business side of this mirror size.  The same could be said for a ~4" or 3" mirror...with respect to a 6".  Afterall, the 8" f/6 is nearly the same package as the 6" f/8.   The question is whether or not producing a 6" mirror is an efficient use of time for a premium optics maker considering the market.  Unless business nearly dries up and one needs some fill work, I don't see how this would make sense. 

 

But that is kinda the thing here.

 

Yeah, anybody in ANY business knows where the "good" money is and where they are kinda wasting their time relatively speaking...

 

Then there are the consumers....that want X....but X is NOT where the good money is...but that is what a few want....

 

And here is the rub....is X something somebody can provide? That is not where most businessness care to play because....welll, that is not where the "good" money is?

 

So, we have two options....nobody provides X because that is not where the "good" money is....which is the current state of affairs appears to be...

 

Or somebody steps up and provides X  and establishes a very narrow  niche market....which may or may not ever happen....


Edited by starcanoe, 27 June 2018 - 09:38 PM.


#17 Jon Isaacs

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Posted 27 June 2018 - 10:19 PM

Mike Spooner has made a number of longer focal length 6 inch F/9's.  If I wanted a top notch longer focal length 6 inch, that's where I would go..  

 

If you pick the mirror up yourself, he might even tell you about the time someone from the Steward lab looked at Jupiter though one of his 6 inch scopes. 

 

Jon


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#18 barbie

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Posted 27 June 2018 - 11:20 PM

I was quite lucky when I bought my 6"F8 Synta(Orion) xt6.  Its optics are so good that I don't really need a premium mirror maker to make me anything better since my Xt6 shows a textbook star test and has been lab tested to be of excellent quality.  Perhaps the Chinese have really gotten the 6"F8 optics to a very high level of performance and Zambuto knows this which is why he doesn't make anything smaller than an 8".  Perhaps not, I don't know for sure but all I can say is that my 6"f8 shows me fantastic views of the planets rivaling those of my apo refractor, but with a little more light grasp for deep sky objects.  About 20 years ago, I had a Bushnell 6"F8 Dob and it was just o.k.  Fast forward to the present and my current 6"F8 dob,  the difference is like night and day in optical performance and mechanics so I would say the Chinese have improved by "light-years", at least when it comes to making 6"F8 mirrors.


Edited by barbie, 27 June 2018 - 11:26 PM.


#19 GShaffer

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Posted 28 June 2018 - 06:46 AM

Mike Spooner has made a number of longer focal length 6 inch F/9's.  If I wanted a top notch longer focal length 6 inch, that's where I would go..  
 
If you pick the mirror up yourself, he might even tell you about the time someone from the Steward lab looked at Jupiter though one of his 6 inch scopes. 
 
Jon


I can 2nd this.... I have a 6.7" f/9.2 quartz that Mike made for me and the more I use it the more I am convinced it is without question as good or better than any optic I have had the pleasure of using.

A couple of DPAC tests at 100 lpi

100lpi in7 (1024x685)small.jpg 100lpi out6 (1024x685)small.jpg
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#20 pstarr

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Posted 28 June 2018 - 11:29 AM

I asked Carl to make me a 6" once and he said he wouldn't do it. He recommended Ed Stevens for a small mirror. Ed is no longer making mirrors. I ended up buying a Parks 6" Mirror and having Dick Wessling refigure it.


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#21 GShaffer

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Posted 28 June 2018 - 12:12 PM

I asked Carl to make me a 6" once and he said he wouldn't do it. He recommended Ed Stevens for a small mirror. Ed is no longer making mirrors. I ended up buying a Parks 6" Mirror and having Dick Wessling refigure it.


My radar is always on for a Stevens mirror to pop up for sale. I have had a 10" f/5 he made for some years now and they don't come any better IMO....The documentation from Ed claims to be a .99 strehl though I have no idea how he arrived at that number. What I do know is when the sky is right it knock your socks off lol

#22 Chesterguy1

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Posted 28 June 2018 - 12:30 PM

While not an explanation, I've heard it said many times on these forums that it's much more likely to get an excellent 6" f/8 from most any of the mass market manufacturers simply because it is less difficult to make.  Even an 8" f/5.7 premium is said to be hard to justify (although I've done it) because there are a plethora of respectable mirrors made at that size/f ratio.  That begins to change at 10" and gets more pronounced as one moves to really big aperture particularly in this age of fast scopes where observers want to be flat footed--whatever the aperture.  As is shown on his website, CZ's standard mirrors are all f/4.5 or faster so one could also ask why not make them at f/4 or f/3.5?  They are certainly more challenging and thus more expensive.  There must be a economic rationale, but, as was said, you could ask him.

 

You don't say why the 6" is so important.  Weight?  At 61 and with modest strength, I have found the 8" quite manageable and can easily lift and cary the complete scope 30, 40, 50 feet.  I got a two-wheel dolly anyway (why risk injury?). There are plenty of posters like Jon Isaac who have no issue lugging a 10".  

 

Gogiboy



#23 starcanoe

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Posted 28 June 2018 - 12:38 PM

.

 

You don't say why the 6" is so important.  Weight?  At 61 and with modest strength, I have found the 8" quite manageable and can easily lift and cary the complete scope 30, 40, 50 feet.  I got a two-wheel dolly anyway (why risk injury?). There are plenty of posters like Jon Isaac who have no issue lugging a 10".  

 

Gogiboy

 

IMO weight is NOT linear.....at some LOW weight it doesn't matter what it weighs....then at some point it gets to where it DOES matter what something weighs....and then you finally get to the point where even a few pounds makes the difference between luggable and not so much. And this applies to costs....size...complexity....bulkyiness...seeing considerations and on an on...

 

And everybody is different. Look at the hundreds....nay thousands of pages where refractor lovers expound on the virtues of small grab and go scopes.

 

A six in f8 made reasonably is a grab and go. An 8 inch a bit less...and 10 inch a bit less than that....and so on a so.

 

You draw the line somewhere. Somebody else draws it somewhere else.

 

In rock climbing there is a saying of sorts. The difference between a 200 foot cliff and a 400 foot cliff is a lot more than 200 feet.


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#24 Jeff Morgan

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Posted 28 June 2018 - 12:59 PM

"Too hard" to do?  No. Lack of a market/profitability? No.

 

If one wants excellence in a small aperture and budget is not a limitation, why not get a refractor?

 

A one-man operation with limited time and limited shop space? I'm surprised Zambuto even bothers with 8" mirrors.


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#25 starcanoe

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Posted 28 June 2018 - 01:06 PM

If one wants excellence in a small aperture and budget is not a limitation, why not get a refractor?

 

A one-man operation with limited time and limited shop space? I'm surprised Zambuto even bothers with 8" mirrors.

 

Budget is almost always a limitation within reason.

 

Have you compared a 6 inch refractor to a 6 inch reflector?

 

You might as well be comparing motorcyles and cars.




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