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

#26 starman876

starman876

    Nihon Seiko

  • *****
  • Vendors
  • Posts: 20368
  • Joined: 28 Apr 2008
  • Loc: VA

Posted 14 April 2018 - 07:12 AM

The first time I had a good night of seeing with my 12.5" porta ball it blew my socks off.  I had never seen such detail before on Jupiter.   I would presume that out of 365 days a year I would have good seeing more than once a year in the DC area.  However, out of all the scopes I have used, 6" AP,  Royce 10" F5, Zeiss, and others, this was the best ever.   It clearly showed me that aperture and premium optics was the only way to go to get the best view on those rare nights.


  • Joe1950 likes this

#27 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18425
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 14 April 2018 - 08:57 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.

A 12" blank seems to be a odd ball size.



#28 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 22928
  • Joined: 22 Feb 2010

Posted 14 April 2018 - 09:26 AM

So Delmarva is a go for next year?  

so far, yep.



#29 dgoldb

dgoldb

    Viking 1

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

Posted 14 April 2018 - 10:45 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.

There are lots of other mirror makers.  Lightholder, Ostahowski, Lockwood, and more.  Do some searches. I would rather refigure your Apertura than order a hubble optics mirror.  Cheaper and more likely to be well figured.  



#30 AlienRatDog

AlienRatDog

    Mercury-Atlas

  • *****
  • Posts: 2973
  • Joined: 15 Jul 2005
  • Loc: Ann Arbor

Posted 14 April 2018 - 11:03 AM

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


That’s my experience as well, my daughter’s XT6 is excellent optically...

#31 TonyStar

TonyStar

    Viking 1

  • *****
  • Posts: 584
  • Joined: 25 May 2013

Posted 14 April 2018 - 11:05 AM

Would a premium 8 inch mirror from the high-end mirror makers out perform, say, a 10 inch Chinese mirror on the planets?  

Premium will give you the certitude that sky, not the telescope is the limit. But eventually, it really depends how good the chinese mirror turns out to be. You'd be surprised with the views a good 12" chinese mirror can provide under steady skies  


  • astroneil likes this

#32 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 15669
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 14 April 2018 - 11:16 AM

You know, it's hard to tell folks premium optics are not good cuz they are good. Its also hard to tell people mass produced optics are necessarily bad cuz they aren't always bad. Its hard to convince either side they're wrong, cuz they're not. :lol:

Edited by Asbytec, 14 April 2018 - 11:17 AM.

  • Jon Isaacs, SandyHouTex, astroneil and 2 others like this

#33 dgoldb

dgoldb

    Viking 1

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

Posted 14 April 2018 - 11:50 AM

You know, it's hard to tell folks premium optics are not good cuz they are good. Its also hard to tell people mass produced optics are necessarily bad cuz they aren't always bad. Its hard to convince either side they're wrong, cuz they're not. lol.gif

The funny part is, it's so easy to just look through each.  Any decent astronomy club or party will have both.  Go see for yourself... 


  • Asbytec and Joe1950 like this

#34 daquad

daquad

    Apollo

  • *****
  • Posts: 1304
  • Joined: 14 May 2008

Posted 14 April 2018 - 01:26 PM

OK, so in good seeing a premium mirror may outperform a mass produced one.  And here we are talking high powers that allows the observer to realize the full resolution capability of the scope, 25X - 50X/inch, which apply to basically four targets and require good seeing.

 

The thing that Newts excel at is deep sky observations, where it is not necessary, nor desirable, in many cases, to use such high powers.  For most of the observing I do, a mass produced Newt is certainly up to the task of providing enjoyable views of most deep sky objects.

 

BTW in good seeing the 10" Orion I had showed plenty of Jupiter's belt detail those very few nights where the seeing would allow a steady image. 

 

Dom Q.


  • Roger Corbett and Joe1950 like this

#35 Joe1950

Joe1950

    Cosmos

  • *****
  • Posts: 9672
  • Joined: 22 Aug 2015

Posted 14 April 2018 - 05:34 PM

That was not done with an interferometer.  

 

Jon

The numbers were not arrived at with an interferometer? I would have thought such high quality figures would need the exactness of an interferometer, Jon.

 

How were they determined?


  • Jon Isaacs likes this

#36 Richard Whalen

Richard Whalen

    Mercury-Atlas

  • *****
  • Posts: 2843
  • Joined: 24 Sep 2007
  • Loc: Florida

Posted 14 April 2018 - 05:46 PM

The numbers were not arrived at with an interferometer? I would have thought such high quality figures would need the exactness of an interferometer, Jon.

 

How were they determined?

Go to CZ site and all is explained. Early on he put out some way inflated numbers. My buddy has one with such documentation, but even a star test shows around 1/6 wave PV.


  • Jon Isaacs and Joe1950 like this

#37 Joe1950

Joe1950

    Cosmos

  • *****
  • Posts: 9672
  • Joined: 22 Aug 2015

Posted 14 April 2018 - 06:12 PM

Hmmmm. Optical quality is a slippery slope. But optical testing is a slippery slope on top of a slippery slope.  scratchhead2.gif


  • Jon Isaacs, airbleeder and earlyriser like this

#38 Allan Wade

Allan Wade

    Soyuz

  • *****
  • Posts: 3932
  • Joined: 27 Jan 2013
  • Loc: Newcastle, Australia

Posted 14 April 2018 - 07:02 PM

If you go with a premium optician, you will almost certainly get a very good mirror. Mass produced mirrors on the other hand can range from very good to poor, so it’s the variability you experience with those mirrors.

 

I had a fairly good 12” mirror in my Orion dob, but when I replaced it with a Zambuto, I saw the light! That piece of glass was a work of art. I’m a fan of premium mirrors from the top guys like Lockwood and Zambuto. You know exactly what you are going to get, and the eyepiece image never fails to amaze.


  • Asbytec, Pinbout, airbleeder and 2 others like this

#39 Richard Whalen

Richard Whalen

    Mercury-Atlas

  • *****
  • Posts: 2843
  • Joined: 24 Sep 2007
  • Loc: Florida

Posted 14 April 2018 - 08:05 PM

In the old days with full thickness large mirrors, even some of the "premium" mirrors for that time rarely produced great images. Just never cooled down, and changed figure all night long. Plus collimation, mirror support issues, non flat secondaries, mechanical flex etc. didn't help. 

 

Im sure on a test bench with controlled environment they showed a good figure, until they were put in a scope and used at night. Same thing still happens, though less so as some mirror makers are trying out new mirror supports, thinner mirrors, and selling to companies that put a premium on mechanics so their mirrors can shine. And with low expansion substrates things get even better. 

 

Some mirror makers and telescope builders have changed with the times, others not so much and are still selling on past reputation. You can have the best figured mirror in the world but if not properly supported, cooled, and in a well built structure it will never live up to its potential. The mirror quality is only part of the equation.


  • Jon Isaacs, SeaBee1, Joe1950 and 1 other like this

#40 Joe1950

Joe1950

    Cosmos

  • *****
  • Posts: 9672
  • Joined: 22 Aug 2015

Posted 14 April 2018 - 08:19 PM

For so long the 1:6 ratio, Pyrex mirrors were the standard. Thinner mirrors were avoided. Thinking has changed, however.

 

It's a very complicated topic. 

 

When Meade first started in the optics/telescope business I bought a 6" f/8 OTA. This was in the 1970s when John Deibel answered the phone and took orders.

 

I put it on an Edmund HD mount. I never used it too much because of other things happening, work, etc. But one night I took it out and looked at Jupiter. It was the best view I ever had and still is the best I've ever seen Jupiter.

 

Don't know if it was a very good mirror, exceptional seeing or a combination of both, but I saw detail I simply couldn't believe.

 

I sold it eventually, and unfortunately.



#41 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 15669
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 14 April 2018 - 09:49 PM

Joe, in my experience, my best views of Jupiter, Saturn, and Mars - ever - were thought a modest obstructed scope in good seeing that was very well collimated and absolutely thermally stable. I mean, seeing so good I could watch the Poison spot form a small hole as it shed a new diffraction ring. You can see this daisy chain behavior in Suiter's illustrations of the diverging light cone. In my experience, and credit to Don for promoting it, the three C's are predominately important: Cooling, collimation, and C'ing. 


  • barbie and Joe1950 like this

#42 Mike B

Mike B

    Starstruck

  • *****
  • Posts: 11002
  • Joined: 06 Apr 2005
  • Loc: shake, rattle, & roll, CA

Posted 14 April 2018 - 09:57 PM

 

The thing that Newts excel at is deep sky observations, where it is not necessary, nor desirable, in many cases, to use such high powers.  For most of the observing I do, a mass produced Newt is certainly up to the task of providing enjoyable views of most deep sky objects.

Newts (ie. "Dobs" in particular) do excel there for the sheer aperture possible for the cost expended. Even the next-best alternative for larger aperture (maybe an SCT?) is getting up there for $$ in the 16" range, and is an absolute beast mount!

 

But speaking of commercially made SCTs, i used a 10" for many years, and it was workable for deep-sky viewing... yet was always frustrating when looking for faint galactic companions to the brighter primaries. Everywhere one looked around the main, brighter galaxy was found "lumpy darkness". bangbang.gif  Planetary nebulae were typically blobby discs, where only glaringly obvious structure could be seen.

 

Thermal management practices were eventually learned & appreciated with the SCT, and some of this situation improved accordingly. Yet even so, average (at best?) optics & a largish CO imparted a rather significant "glass ceiling" on what could be seen with this scope.

 

Transmute this scenario onto a commercially mass produced 10" Newtonian with optics "average" for the species (whatever that might construe). You'd be substantially ahead of the above SCT scenario if for no other reason than having only TWO reflective surfaces between the stars & premium glass (eyepiece), plus a ~25% CO. Your "lumpy darkness" factor is notably reduced, your contrasts improved, your thermal gremlins more "open" to resolution, and quite likely your functional magnification range expanded.

 

That latter aspect will allow you to dig down deeper toward resolving some borderline globulars into stars, revealing to your eye more structure in PNs, and maybe even snagging a few progenitor stars in those PNs! Magnification definitely plays a role in deepsky!

 

Now take that last scenario & swap out mass-produced "average" optics for a "premium" set, possibly with a 17-20% CO. All of the above effects & advantages will be amplified yet one more notch! Assuming the air you're viewing thru will cooperate, and all user details have been properly attended. There are ample threads here on CN regarding what has best been termed "the three C's"; cooling, collimation, and conditions.

 

I've personally seen just a little & limited set of such examples, but enough to know they're there. But i've seen boatloads of examples in my current 15" Dob, having "premium" optics, and a 17% CO. The air is ALWAYS the limiting factor! Always. I'll go weeks & months of decent to good to very good views, and imagine that i've seen the best it can give me. And then, one random nite, some One flips on the magic switch... the seeing goes into "glass" mode, and Jupiter (notoriously shy about revealing much) suddenly goes "Hubble" on me in the eyepiece! bigshock.gif 15-inches is suddenly permitted to perform at the 15-inch level... photographic detail in the EP!

 

Seen the same thing when transparency joins the seeing party in the "excellent" department. You can suddenly see EVERYthing deepsky! The notion grips you that your next meaningful optical upgrade is gonna involve a realtor, not an optician. 

 

Wouldn't stock, average, mass optics enjoy the same benefits under those same conditions? Undoubtedly. But after years & years of looking thru such scopes, i'd never ONCE seen such a stark, in-your-face, transition in the images rendered! Two scopes in particular have been responsible for illustrating this for my eyes, this Dob being the second, but a humble 6" F8 1960's vintage Newt flung that "premium" door open wide.

 

Once you've taken a long, magical look thru that open door, and entered in, there is no going back.

 

So assuming you've collimated well, cooled the thermals & lassoed the currents, positioned the scope away from thermal heat-sinks, and aren't viewing thru their influence in the near environment, and assuming the lower & upper atmo at your site can provide stable seeing often enough... "premium" optics will deliver the goods like nothing else can or will! rockon.gif


  • George N, JimMo, Mike Spooner and 2 others like this

#43 barbie

barbie

    Viking 1

  • *****
  • Posts: 986
  • Joined: 28 Jan 2013
  • Loc: Northeast Ohio

Posted 14 April 2018 - 10:30 PM

Joe, in my experience, my best views of Jupiter, Saturn, and Mars - ever - were thought a modest obstructed scope in good seeing that was very well collimated and absolutely thermally stable. I mean, seeing so good I could watch the Poison spot form a small hole as it shed a new diffraction ring. You can see this daisy chain behavior in Suiter's illustrations of the diverging light cone. In my experience, and credit to Don for promoting it, the three C's are predominately important: Cooling, collimation, and C'ing. 

That would "mirror" my experiences as well.  My "modest", well cooled and collimated 6" F8 Dob has given me some of my best views of the planets in the last 30 years!  Over those past 30 years, I've had a lot of scopes from refractors(apo and long focus achro) to maksutovs, an SCT, and Newtonians both large and small including a Cave Astrola Deluxe 10" F7 from the mid 1960's vintage and out of all of these instruments, my 6 inch F8 Newtonian has been my most used and enjoyed instrument on the planets as well as doubles and deep sky objects.smile.gif


Edited by barbie, 14 April 2018 - 10:32 PM.

  • Asbytec, paul m schofield and Joe1950 like this

#44 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 15669
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 14 April 2018 - 10:40 PM

Actually, Barbie, after stepping down from my C11, I find my 6" MCT is - by far - my most used scope, as well from a range of scopes from small achros to an 18" Dob. You should see the scars on the mounting cradle and dovetail mount. I even broke my slow motion knobs cuz of extensive wear. :lol: 


  • Joe1950 likes this

#45 Joe1950

Joe1950

    Cosmos

  • *****
  • Posts: 9672
  • Joined: 22 Aug 2015

Posted 15 April 2018 - 02:21 AM

Barbie, you and Norme have learned the skill of observing, seeing what is there, but not jumping out like a processed image. It takes practice and patients to become a good observer but it can be done and done without perfect optics.

 

Too many any of us are overly concerned with wavefront numbers, Strehl ratios and fall into the “this versus that” trap. We spend more time looking for flaws rather than training our eyes and mind to see the subtle details presented us.


  • Asbytec, paul m schofield, barbie and 2 others like this

#46 CHASLX200

CHASLX200

    Hubble

  • *****
  • Posts: 18425
  • Joined: 29 Sep 2007
  • Loc: Tampa area Florida

Posted 15 April 2018 - 06:14 AM

My best views at powers from 700 to 1150x were with my 11" to 18" Zambuto and OMI mirrors.


  • Joe1950 likes this

#47 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 15669
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 15 April 2018 - 06:21 AM

Sometimes I think we argue too much about our equipment and less about what we do with it. It's almost like the holy grail of observing is our equipment. It's not. The holy grail is our self. We can make gains with better equipment, but much more meaningful gains by improving what we can make of the telescopic image presented to us. Premium or otherwise.

 

There is probably a huge difference between what the scope can deliver to it's focal plane and be imaged and what we can make of it visually. This implies the scope has done its job to provide a nice image, but we have our work cut out for us seeing the image as well as humanly possible.

 

Observing is a difficult undertaking requiring a lot of work to close that gap. The scope doesn't really help us here, it's job is done. Observing is on us, it's our responsibility. It's a physiological pursuit more so than an mechanical one. I believe it's more about us than it is about our equipment. 

 

I observed Messier 109 last night and could make out its core, extended bar, and a faint halo in a 6" aperture. This is a dim galaxy. The cheapo scope didn't hand it to me on a silver platter, I had to work to see it using some basic telescopic principles and knowledge of physiology. But, the point is, nothing prevented me from seeing it. Not the obstruction, not spherical aberration, nor anything else. 

 

Edit: Thinking further. There is absolutely nothing wrong with demanding the best equipment and keeping pressure on the industry to deliver. And we should all be grateful a handful of skilled glass pushers are keeping the art alive. 


Edited by Asbytec, 15 April 2018 - 07:37 AM.

  • Jon Isaacs, Mike B, Pierre Lemay and 4 others like this

#48 Mike B

Mike B

    Starstruck

  • *****
  • Posts: 11002
  • Joined: 06 Apr 2005
  • Loc: shake, rattle, & roll, CA

Posted 15 April 2018 - 09:47 AM

 

Edit: Thinking further. There is absolutely nothing wrong with demanding the best equipment and keeping pressure on the industry to deliver. And we should all be grateful a handful of skilled glass pushers are keeping the art alive.

A phenomenon pertinent to all walks of life, whether the skilled worker is wisely & effectively repairing your car, or building a masonry fireplace that will actually "draw" properly & fill your home with warmth... as opposed to smoke.


  • Asbytec and Joe1950 like this

#49 Pinbout

Pinbout

    ISS

  • *****
  • Posts: 22928
  • Joined: 22 Feb 2010

Posted 15 April 2018 - 09:52 AM

Sometimes I think we argue too much about our equipment and less about what we do with it.

 

waytogo.gif


  • Jon Isaacs, Pierre Lemay, SeaBee1 and 1 other like this

#50 gwlee

gwlee

    Surveyor 1

  • *****
  • Posts: 1692
  • Joined: 06 Sep 2015
  • Loc: 38N 120W

Posted 15 April 2018 - 10:30 AM

The funny part is, it's so easy to just look through each.  Any decent astronomy club or party will have both.  Go see for yourself... 

That can be an option for people who live in metro areas, not so easy for us rural dwellers. For us, CN is our astronomy club.


Edited by gwlee, 15 April 2018 - 11:18 AM.

  • JKAstro and starzonesteve like this


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