Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Premium mirror vs. Chinese mirror

  • Please log in to reply
92 replies to this topic

#1 Richard Turner

Richard Turner

    Mariner 2

  • *****
  • topic starter
  • Posts: 223
  • Joined: 25 Jan 2009
  • Loc: NC

Posted 13 April 2018 - 03:46 PM

Forgive me if this has been asked a thousand times before.

 

Would a premium 8 inch mirror from the high-end mirror makers out perform, say, a 10 inch Chinese mirror on the planets?  My wish is for great images of  the planets  when seeing allows.  Maybe the answer should be obvious, but I would like those in the know to chime in.  I have and have had Chinese reflectors a long time now.  I was thinking about investing in an 8 inch premium mirror.  Finances won't allow me to go larger.

 

Thanks for anyone who is willing to offer advice.

 

Richard Turner

North Carolina



#2 Jim Waters

Jim Waters

    Mercury-Atlas

  • *****
  • Posts: 2962
  • Joined: 21 Oct 2007
  • Loc: Phoenix, AZ USA

Posted 13 April 2018 - 03:53 PM

Simple answer - YES

 

The best of the best - http://zambutomirrors.com/


  • Markovich and Joe1950 like this

#3 Markovich

Markovich

    Viking 1

  • *****
  • Posts: 791
  • Joined: 22 May 2007
  • Loc: Grove City, Ohio

Posted 13 April 2018 - 03:55 PM

Yes- all things being equal go with a premium mirror and builder


  • Jim Waters and Joe1950 like this

#4 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 22925
  • Joined: 22 Feb 2010

Posted 13 April 2018 - 04:17 PM

Forgive me if this has been asked a thousand times before.

 

Would a premium 8 inch mirror from the high-end mirror makers out perform, say, a 10 inch Chinese mirror on the planets?  My wish is for great images of  the planets  when seeing allows.  Maybe the answer should be obvious, but I would like those in the know to chime in.  I have and have had Chinese reflectors a long time now.  I was thinking about investing in an 8 inch premium mirror.  Finances won't allow me to go larger.

 

Thanks for anyone who is willing to offer advice.

 

Richard Turner

North Carolina

I heard Steve Dodd has really low prices for refiguring- actually the lowest I’ve heard, lower than what I would want to refiguring a mirror. Look at the 14” in the classifieds $900.


  • CollinofAlabama, George N, ShaulaB and 1 other like this

#5 petert913

petert913

    Gemini

  • *****
  • Posts: 3345
  • Joined: 27 May 2013
  • Loc: Portland, OR

Posted 13 April 2018 - 04:33 PM

Wow, one year backlog on Zambuto mirrors.  They are located fairly near me - I wonder if Carl gives tours of the fabrication shop? cool.gif


  • Joe1950 likes this

#6 daquad

daquad

    Apollo

  • *****
  • Posts: 1300
  • Joined: 14 May 2008

Posted 13 April 2018 - 07:01 PM

Well, the 8" f/4.5 Zambuto mirror only at $1100 costs twice as much as a Chinese 8" Dob with all the fixin's  Only you can decide if it is worth those rare exceptional views that a premium mirror will provide in excellent seeing. 

 

How often do you experience seeing that will allow the full resolution of an 8 or 10 inch scope?  Where I live in southern New England, a 10" Orion Newt often showed as much, and sometimes more, detail on Jupiter than a 6" f/9 AP Starfire triplet.  Maybe I had an exceptional example in the 10", but what would it cost you to try one?

 

It's nice knowing that you have the best 8" Newtonian optics that money can buy, but it is also nice to know that your run-of-the-mill 10" Newt can show you the same views as a premium 6" APO.

 

Dom Q.


  • CollinofAlabama, Jon Isaacs, Phil Cowell and 5 others like this

#7 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 22925
  • Joined: 22 Feb 2010

Posted 13 April 2018 - 07:07 PM

https://www.cloudyni...rror-excellent/


  • Jim Waters and Joe1950 like this

#8 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18414
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 13 April 2018 - 07:17 PM

Forgive me if this has been asked a thousand times before.

 

Would a premium 8 inch mirror from the high-end mirror makers out perform, say, a 10 inch Chinese mirror on the planets?  My wish is for great images of  the planets  when seeing allows.  Maybe the answer should be obvious, but I would like those in the know to chime in.  I have and have had Chinese reflectors a long time now.  I was thinking about investing in an 8 inch premium mirror.  Finances won't allow me to go larger.

 

Thanks for anyone who is willing to offer advice.

 

Richard Turner

North Carolina

99% of the time it would.  Unless you got a freaky bad mirror from a top notch mirror maker and got a freaky good mirror from a China scope by mistake.  I could never live without having the best mirror.


  • Joe1950 likes this

#9 gwlee

gwlee

    Surveyor 1

  • *****
  • Posts: 1688
  • Joined: 06 Sep 2015
  • Loc: 38N 120W

Posted 13 April 2018 - 07:38 PM

Forgive me if this has been asked a thousand times before.

 

Would a premium 8 inch mirror from the high-end mirror makers out perform, say, a 10 inch Chinese mirror on the planets?  My wish is for great images of  the planets  when seeing allows.  Maybe the answer should be obvious, but I would like those in the know to chime in.  I have and have had Chinese reflectors a long time now.  I was thinking about investing in an 8 inch premium mirror.  Finances won't allow me to go larger.

 

Thanks for anyone who is willing to offer advice.

 

Richard Turner

North Carolina

I owned a good, but inexpensive 8” Chinese Dob and a cusom 8” Dob with zambuto optics for several years and had many opportunities to operate them side by side. The differences in the optics were subtle, requiring very good seeing to discern.

 

I did not own a 10” Chinese Dob to compare, but I would be very surprised if a garden variety 10” glass wouldn’t easily best my 8” Zambuto. The 2” difference in aperture is an overwhelming advantage and not anywhere near as subtle. 

 

However, for the person who wants better views, but doesn’t want to handle a larger scope, premium optics are the only game in town. The larger scope will give better views for less money, and it will be available off the shelf. 


  • David Knisely, Jon Isaacs, stevew and 12 others like this

#10 Joe1950

Joe1950

    Cosmos

  • *****
  • Posts: 9599
  • Joined: 22 Aug 2015

Posted 13 April 2018 - 08:00 PM

0.999 Strehl. 1/182λ RMS, 1/60.8λ P-V, signed by CZ ...Doesn't get any better than that.

 

I wonder if he has a senior discount? scratchhead2.gif  Like 97% Off every Wednesday. Or a shorter senior wait time, which could be very important.  thinking1.gif

 

The chances of living past 115  YO are 1 in 2 Billion. The chances of getting a production mirror as good as above are far, far less, but not zero. If one were produced and was shipped out, no one would know, since I doubt the testing abilities come anywhere close to the tolerances mentioned for the Z optics, if testing is done at all.

 

However, it's true, a couple inches of aperture on a decent optic would be very noticable if one can handle the build. shrug.gif


  • Jim Waters and big_scot_nanny like this

#11 SeaBee1

SeaBee1

    Soyuz

  • *****
  • Posts: 3837
  • Joined: 19 Mar 2015
  • Loc: Under the DFW light barrier

Posted 13 April 2018 - 09:05 PM

When I jumped into this ATM thing face first, I was facing the same dilemma... get one off the GSO shelf or go premium... after a LOT of soul searching and getting to know me better, I went with a 10 inch Royce conical (probably one of the last he made before retiring). My reasoning was thus: If I got the GSO 10 inch, I would ever wonder if I did the right thing. Since I got the Royce, I have never wondered and sleep very well at night now.

 

Now, for the rest of the story... on most nights, I doubt very seriously that much difference could be discerned between my Royce and a Chinese mirror, at least not by me. But I have had the Royce out on a few exceptionally good nights and the image was OMG good, so good, I am not really sure how to describe it convincingly. Exceptional clarity? Knock your socks off contrast? Hold the phone Mom, you gotta come see this?

 

I will NEVER part with my Royce mirror. I am not convinced I could ever say that about a Chinese mirror.

 

And just to be clear, I do not think there is anything wrong with Chinese mirrors. Most people in this hobby use them to great satisfaction. And I could have as well... except for the wondering...

 

Keep looking up!

 

CB


  • CollinofAlabama, Richard Turner, paul m schofield and 1 other like this

#12 dgoldb

dgoldb

    Viking 1

  • -----
  • Posts: 873
  • Joined: 23 Oct 2015

Posted 13 April 2018 - 09:08 PM

8" premium costs the same as a 16" GSO, so that's really a more apt comparison.

 

But if comparing 8" premium to 10" GSO, I'd much prefer the premium.  It has a higher likelihood of being a great performer.    


  • Joe1950 likes this

#13 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 22925
  • Joined: 22 Feb 2010

Posted 13 April 2018 - 09:10 PM

0.999 Strehl. 1/182λ RMS, 1/60.8λ P-V, signed by CZ ...Doesn't get any better than that.

 

I wonder if he has a senior discount? scratchhead2.gif  Like 97% Off every Wednesday. Or a shorter senior wait time, which could be very important.  thinking1.gif

 

The chances of living past 115  YO are 1 in 2 Billion. The chances of getting a production mirror as good as above are far, far less, but not zero. If one were produced and was shipped out, no one would know, since I doubt the testing abilities come anywhere close to the tolerances mentioned for the Z optics, if testing is done at all.

 

However, it's true, a couple inches of aperture on a decent optic would be very noticable if one can handle the build. shrug.gif

You can always come to Delmarva next year and make one just as good...if your lucky

 

some people start off just doing things correctly. Others like me keep going around in circles till we learn to do it right...

 

73EE032A-62CC-4F47-8B32-8A129D992049.jpeg


Edited by Pinbout, 13 April 2018 - 09:11 PM.

  • George N, Joe1950 and Lukes1040 like this

#14 barbie

barbie

    Viking 1

  • *****
  • Posts: 979
  • Joined: 28 Jan 2013
  • Loc: Northeast Ohio

Posted 13 April 2018 - 11:54 PM

I'm not sure what the Chinese did on my 6"F8 Mirror but it performs as well as my former 5" apo refractor(compared the two side by side)!!

Whatever or however Synta ground and polished the mirrors, they clearly showed attention to detail and did it the right way!!  I've had numerous experienced mirror makers(in addition to myself)  as well as an independent optical testing lab test the mirrors and they were extremely impressed!

You can have the scope when you pry it out of my cold, dead hands!!grin.gif


Edited by barbie, 13 April 2018 - 11:57 PM.

  • Shneor, AlienRatDog, Stephen Kennedy and 1 other like this

#15 avid_dk

avid_dk

    Vostok 1

  • -----
  • Posts: 118
  • Joined: 18 Dec 2017
  • Loc: SW Oregon, SW USA

Posted 14 April 2018 - 12:00 AM

You can always come to Delmarva next year and make one just as good...if your lucky

 

 

So Delmarva is a go for next year?  



#16 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 15621
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 14 April 2018 - 12:56 AM

A premium obstructed 8" aperture with a 0.2D obstruction and 0.98 Strehl packs 90% of the light in the central disc of about 0.68" arc. That's about 76% of the 84% total light possible. Sometimes I think we are rightfully awed by the high Strehl and fine wavefront error for premium optics and forget they are affected by diffraction, too. Only 76% of the light? Yuk! smile.gif

 

In comparison, a nearly true "diffraction limited" 10" aperture with a 0.2D obstruction and 0.8 Strehl packs 73% of the light in its smaller central disc of about 0.55" arc. That's about  61% of the 84% light possible in the Airy Disc, about 15% less than the premium. The decrease in encircled energy is significant, especially for a same aperture comparison. But with a larger aperture, it's also delivered to a smaller angular area including the offending first diffraction ring. Especially in average seeing. 

 

Consider most of the light on the aberrant and obstructed 10" is displaced into the first ring at 184/Dmm out to about 0.72" arc. That's pretty close to the same as the Airy Disc of the 8" premium both with a bunch of light packed into about the roughly the same 0.7" angular diameter. In seeing, I imagine this difference is negligible given the aperture difference. 

 

The observable spurious discs of both are somewhat smaller than the Airy disc, with the still often visible 10" spurious disc being a little smaller. Consider average seeing is about Pickering 5/10 (R0 ~ 100mm), where the central spurious disc is blurred slightly, and both are just below the diffraction limit, in this case, due to seeing induced FWHM. The smaller 10" spurious disc could still prevail in terms of short exposure "snapshot" seeing. 

 

I think, as always, the premium scope will enjoy slightly better contrast out to a couple arc seconds with less light in the rings and this is what skilled observers notice especially on nights with better seeing. But, I bet it would be hard to tell the difference in average seeing as the increased aperture makes up some of the ground lost to the deservedly premium optic. And assuming the Chinese cheapo 10" produces a relatively clean PSF without any other major faults. 

 

I like gwlee's comment above. It makes sense. As Joe says, it does not get any better than a premium optic. That's absolutely true. As Seabee says, he has piece of mind. I've had some nights with good seeing that blew my socks off, too. No doubt a premium optic shines in this case and substantiates the anecdotal evidence in support of premium optics. As Barbie says, some Chinese producers are doing alright. I have one. And I observe in normally better than average seeing. Gimme that, anyday. 

 

A scope with a nice Strehl of 0.95 and an obstruction near 30% can pack 80% if the light in the central disc meeting the intent of the Rayleigh criterion of (presumably smooth) 1/4 pvw LSA and a Strehl of 0.8 or near the Marechal criterion of 1/14 wave RMS. That's about 67% of the 84% possible (Double yuks! :lol: ) diffracted and aberrated light in the central disc on the focal plane. If you can get there, though, you're fine IMO and IME. Anything better is gravy and probably worth paying for, if you're so inclined. Why? Because while a good scope is good, it does not get any better than premium. 


Edited by Asbytec, 14 April 2018 - 12:58 AM.

  • Richard Turner, Oberon, SeaBee1 and 1 other like this

#17 39.1N84.5W

39.1N84.5W

    He asked for it

  • *****
  • Posts: 3964
  • Joined: 24 Oct 2006
  • Loc: cincinnati

Posted 14 April 2018 - 04:00 AM

It's this reason that I went with a Lockwood 10" f6.15 mirror in a Teeter's STS format, smaller secondary. Why not get the best you can afford? You work hard and it's nice to have great gear under the night sky.
  • spencerj, Mike B, Jeff B and 4 others like this

#18 Ian Robinson

Ian Robinson

    Voyager 1

  • *****
  • Posts: 10698
  • Joined: 29 Jan 2009
  • Loc: 33S , 151E

Posted 14 April 2018 - 04:20 AM

yet most are very happy with their mass made mirrors ....

 

Personally - I'd rather a diffraction limited 16 in mirror which will take me a lot deeper and will work just fine for viewing most everything over a premium 6in mirror which is as close to perfect on the front surface as a human can make it which will only be working perfectly one or two hours a year under the best possible seeing.

 

For me ---- the more light I can gather and get usuable viewing / imaging from for the $ the better, and I suspect this applies to 95% of amateurs. We aren't all millionaire selffunded retirees who can throw lots of $ at small extreme quality telescopes.


Edited by Ian Robinson, 14 April 2018 - 11:21 PM.

  • Pierre Lemay, Mike G., Joe1950 and 1 other like this

#19 39.1N84.5W

39.1N84.5W

    He asked for it

  • *****
  • Posts: 3964
  • Joined: 24 Oct 2006
  • Loc: cincinnati

Posted 14 April 2018 - 04:27 AM

...most...

Your mileage may vary.
  • Joe1950 likes this

#20 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 15621
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 14 April 2018 - 05:04 AM

Yea, there is no argument premium mirrors are as good as it gets. And consistently so. Mass produced mirrors are often of lesser quality, some are dogs, and some are amazing. It's hit and miss. But seems more likely a hit these days, at least for a mirror that is good enough to show what is there to be seen. The only difference is how well you see it (with some tiny low contrast exceptions.) 

 

I'd wager, since we often talk about our equipment, we often forget about the most important variable in the entire wobbly stack. That is the observer. I'd bet there are larger gains to be had by increasing our observing skills in a given aperture than improving our wavefront. Our telescope may put up a nice image, but it is entirely up to us to see as much of that nice image as is humanly possible. 


  • Richard Turner, paul m schofield, SeaBee1 and 1 other like this

#21 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 78919
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 14 April 2018 - 05:07 AM


0.999 Strehl. 1/182λ RMS, 1/60.8λ P-V, signed by CZ ...Doesn't get any better than that.

 

 

 

 

That was not done with an interferometer.  

 

Jon


  • Richard Whalen, Mike G. and Joe1950 like this

#22 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18414
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 14 April 2018 - 05:50 AM

yet most are very happy with their mass made mirrors ....

 

Personally - I'd rather a diffraction limited 16 in mirror which will take me a lot deeper and will work just fine for viewing most everything over a premium 6in mirror which is as close to perfect on the front surface as a human can make it which will only be working perfected one or two hours a year under the best possible seeing.

 

For me ---- the more light I can gather and get usuable viewing / imaging from for the $ the better, and I suspect this applies to 95% of amateurs. We aren't all millionaire selffunded retirees who can throw lots of $ at small extreme quality telescopes.

99% of people don't know any better.  Once they have looked thru a top notch mirror and seen Jupiter or the moon at 700x on my best nites they would never be the same.  Most people just look and don't bother with collimation, cooling and or seeing.  I was the same way at age 13 and knew no better. We all start out not knowing, that is part of the thrill, learning as we go.


  • Mike B, sglamb and Joe1950 like this

#23 jring

jring

    Messenger

  • -----
  • Posts: 458
  • Joined: 23 Sep 2016

Posted 14 April 2018 - 06:04 AM

Hi,

quite frankly, I don't think the difference will be huge between a good example of chinese 10" and an 8" premium. And I'm not sure which one will show a better image...

 

Figure is usually quite good nowadays on small and not too fast mirrors from Synta and GSO - the question is if the glass is well annealed and there will be some roughness in the surface.

 

If I had a 10" GSO, I would certainly do star tests and try to find out if the mirror is good. Getting some more opinions among friends, at a telescope meeting or in a club or even in here by posting images is a good idea.

 

If the results are not satisfactory, one could get the mirror tested and maybe refigured - if the glass is not strained, which has happened with chinese glass.

 

Also, sometimes with patience, a premium mirror comes up used... without waiting time and cheaper than new...

 

Joachim


  • Jon Isaacs, Richard Turner and Joe1950 like this

#24 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 15621
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 14 April 2018 - 06:16 AM

99% of people don't know any better.  Once they have looked thru a top notch mirror and seen Jupiter or the moon at 700x on my best nites they would never be the same.  Most people just look and don't bother with collimation, cooling and or seeing.  I was the same way at age 13 and knew no better. We all start out not knowing, that is part of the thrill, learning as we go.

That's probably true. I learned to tend to collimation and thermal management. The most eye opening thing is, as you probably know, to have amazing seeing as often as possible. You can really dial in collimation. Once you notice the difference between a blurry Jove flapping in the wind and a beautifully 'etched' image, there is no going back (metaphorically speaking).

 

I was observing on the leeward side of a mountain range, ironically, but it was such that a laminar eddy formed overhead. So much so, you can see the leeward eddy on some weather charts. Seeing was almost always 8/10 or better overhead. I could watch Jupiter move westward out of that smooth eddy and just fall apart within a few minutes. Strange thing to see. 

 

I have seen seeing so steady, and maybe you have too, I can watch the Poisson spot during defocus as it rolls between being a tiny spot to developing a small hole in the center as it gives birth to the next diffraction ring. You can see this daisy chain behavior in a few of Suiter's illustrations. When you get nights like that, (most) every scope rocks. It's in seeing like that I learned to appreciate my mass produced scope from China. I'll take a premium mirror any day, but with seeing like that I really don't feel the need. 

 

The other appreciation I learned is not rely on a telescope to show me it's image. I realized it's not going to do that, it will not inject every ounce of resolution or every photon into my visual system against my will. I (we) have to take responsibility for seeing the image it  forms and make the most of what we can possibly see right to the edge of our visual noise level and imagination. And interpret what is being seen with confidence. Once you can do that, you realize how well some scopes perform despite their aberrations and obstructions. I'll take a larger aperture any day, too, but when you drain your scope's image for every ounce of detail you can possibly observe, I really don't feel the need, either. 

 

I was talking about lunar "sharpness" with a guy who has a 6" APO. We discussed hills on the lunar limb and what we saw of them. It turns out, we see pretty much the same thing, but his image was a little sharper. His shadows maybe a little darker. I like what Jon said in another thread, if I may paraphrase him, a good telescope shows you what's there to be seen. I sometimes think to get a nice APO, I have a few bookmarked in my wish list. But after a nice evening with Jupiter I always ask myself, "why"? Again, I no longer feel the need. All thanks to learning to drain a Chinese cheapo for everything I can make of its image in the most excellent seeing. 


Edited by Asbytec, 14 April 2018 - 06:27 AM.

  • Jon Isaacs, Pierre Lemay, daquad and 1 other like this

#25 hdavid

hdavid

    Vostok 1

  • -----
  • Posts: 130
  • Joined: 12 Feb 2017

Posted 14 April 2018 - 07:01 AM

So is it the consensus that Zambuto makes the best mirrors these days?  My problem: I can't get their 12.5" mirror in my 12" tube (and I really like the tube).

 

What about a Hubble Optics sandwich mirror?  Comes in 12".  Would it be noticeably better than my current 12" Apertura mirror (Taiwan I think)?  In keeping with the thread, what's the consensus on Hubble sandwich mirrors generally?  Any other ideas for a quality 12" mirror.




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics