Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Reflectors

Pages: 1 | 2 | 3 | 4 | 5 | 6 | (show all)
Peter Natscher
professor emeritus


Reged: 03/28/06

Loc: Central Coast California
Re: Top Opticians in the US for reflectors new [Re: Starman1]
      #5691584 - 02/20/13 07:29 PM

Each mirror maker offers different options. Some don't figure mirrors faster than F/4.5 or 4.0. Others don't make anything larger than 16" or 20" or less than 22" aperture. Before choosing a mirror maker, it depends on what kind of mirror you are after. For instance, Steve Kennedy and Mike Lockwood are the only premier fast mirror makers producing top quality mirrors below F/4.0 and at apertures far larger than 24" -- and these two really shortens the list. Steve Kennedy broke this important barrier first back in 2005. Steve came out of Celestron and has make over 2,000 mirrors to date. Before Steve K., there were only custom-figured mirrors at F/ 4.X and slower for amateurs. CZ only recently has moved to a faster F/4.0 after many years at F/4.3-5.X.

Post Extras: Print Post   Remind Me!   Notify Moderator  
davidpitre
Post Laureate
*****

Reged: 05/10/05

Loc: Central Texas
Re: Top Opticians in the US for reflectors new [Re: ml96737]
      #5691758 - 02/20/13 09:00 PM

Quote:

John Hall of Pegasus produced several bad ones, and even tried to cover it up by false testing and threaten Mr. Rohr! http://www.astro-foren.de/showthread.php?10080-Pegasus-Newton-320-1500 )





I don't want to pile on or hurt feelings, but John Hall has produced more than a few stinkers. I owned one, and have talked with a number of folks who felt likewise about their experience. I don't know about his better mirrors (and I'm sure some will chime in about their good mirrors) but because of consistency issues, he should not be listed with the "top".


Post Extras: Print Post   Remind Me!   Notify Moderator  
ausastronomerModerator
Carpal Tunnel
*****

Reged: 06/30/03

Loc: Kiama NSW (Australia)
Re: Top Opticians in the US for reflectors new [Re: Mike Lockwood]
      #5691771 - 02/20/13 09:19 PM

Quote:

It is important to note, though, that a defect once in a great while is much different and far less concerning than gross, frequent, or systematic errors, which, sadly, I have seen quite often in mirrors that come to me for testing.

However, it's how one handles a mistake that is important. If it happens, I won't react with denial or by abusing, belittling, or blaming the customer - I will check out the mirror and fix it if there is an issue. I will also explain what happened to the client and do my best to never make the same mistake again.




Hi Mike,

You make some extremely good points and it's a pity all opticians don't take a leaf out of your book. Everyone is human and will make a mistake at some time in their life. How they handle it is what matters. If it's properly handled it will just fall through the cracks. The customer will be out a little in observing time and use of the scope, he won't be out of pocket financially. In these situations invariably the opticians reputation will remain in tact, if not enhanced due to the good customer service and fault rectification.

Unfortunately a couple of opticians who continually get glowing reports on internet forums; and already given a big rap by several people in this thread, have a less than favourable success rate IME and unfortunately have not even wanted to hear about the lemon they produced, or wanted to rectify the issues, when confronted about them. The people offering favourable comments on internet forums usually give their positive reports based on their sample of one good mirror that they may have experience with, and not be aware of the number of not so good mirrors these opticians have produced. I know you have had to refigure a couple of these lemons. Mark Suchting had to deal with another. In all cases at no cost to the optician who produced the lemon. I am aware of a couple more that are yet to be refigurred and the owner has continued to tolerate a less than acceptable optic for the money paid.

Unfortunately in the world of constant litigation which we now live in, people keep pretty tight lipped about their bad experiences.

It's a pity they can't all deal with a bad mirror in the fashion you have outlined.

Cheers,


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Top Opticians in the US for reflectors new [Re: Peter Natscher]
      #5691844 - 02/20/13 10:10 PM

Nice points Don. I'd bet they all can and have produced fine mirrors but consistency would seem to be one of the real TOP GUN attributes of the best.

Pete


Post Extras: Print Post   Remind Me!   Notify Moderator  
azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Top Opticians in the US for reflectors new [Re: siriusandthepup]
      #5691859 - 02/20/13 10:19 PM

Quote:

Quote:

I'd be curious to know what happened to George Clements - the PARKS OPTICAL optician at least circa 1990s. Got two essentially perfect mirrors from him. Never hear of him however.

Pete




+1

I would love to know about this guy also. I have one of his 8" f/6 Parks mirrors and it is exquisite! I wasn't able to track down much information for him at all.




Lol, love your qoute in your signature.

Yeah, I've googled for Clements and he's not to be found. I spoke to him once over the phone, its not like he was some old codger. It'd be interesting to find out what happened.

Pete


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: Top Opticians in the US for reflectors [Re: Norm Meyer]
      #5691864 - 02/20/13 10:24 PM

Quote:

What about Mark Harry he makes excellent small to
medium sized mirrors. I have one of his 8" F7.5 mirrors
and it is excellent.

Norm




up to 14in and is quick. I wish I could get one of his... but I'm aflicted with poor artist syndrome...


Post Extras: Print Post   Remind Me!   Notify Moderator  
jpcannavo
scholastic sledgehammer
*****

Reged: 02/21/05

Loc: Ex NYCer, Now in Denver CO!
Re: Top Opticians in the US for reflectors new [Re: ausastronomer]
      #5692286 - 02/21/13 07:30 AM

Quote:


Unfortunately in the world of constant litigation which we now live in, people keep pretty tight lipped about their bad experiences.




And there is another force that might be at wok here as well. If one were to get a lemon from one of the "real big names", there may be fear that publicizing it, on a forum such as this, would rattle "cherished beliefs" and be taken as somehow being politically incorrect, possibly generating hostile responses. I myself fell victim to this sort of hesitance, not being able to bring myself to "out" the very well know optician who gave me a less than up to spec mirror, that moreover remained unimproved after returning it for a touch-up.
What we really need is some organized body of objective consumer reporting. We have some of this - Wolfgang Rohr, etc. - but not nearly enough. I do think I remember a while back Dave Bonandrini talking about an upcoming/ongoning report on the third party testing of a large number of commercial mirrors - including those made by our cherished premium "luthiers" - but I don't think it materialized. Interestingly, the big sources for objective info - S&T and Astronomy mag etc. - will publish monthly objective evals of commercial scope and equipment, but not individual mirrors. Wouldn't it be neat to see S&T have a monthly column called "Mirror Test Reports".
Given our intense focus (!) on optical quality, it is indeed strange that very little of this actually happens. This absence is even evident in our forums. While they do have review sections, look at the categories. There is no specific section dedicated to reports on mirrors. Sure they report on large and small dobs, etc, but this is not quite the same thing, and parallels the similar absence in our our magazines. Strange indeed.

Edited by jpcannavo (02/21/13 09:54 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Darren Drake
Carpal Tunnel
*****

Reged: 10/09/02

Loc: Chicagoland
Re: Top Opticians in the US for reflectors new [Re: jpcannavo]
      #5692394 - 02/21/13 09:26 AM

Yes Wolfgang Rohr's website is an amazing source of info on so many mirrors and lenses along with their detailed reports. It can be a little frustrating reading through the translated German but still I find myself going through the many reports frequently so as to familiarize myself with the general quality and consistency of various lens and mirror makers. I wish there were more sites like this one especially in English. The book Bonandrini mentioned here a few years ago has apparently been mothballed or seriously delayed. In any event I hope another optical testing site makes an appearance sometime in the not to distant future.

Edited by Darren Drake (02/21/13 01:43 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
EJN
Carpal Tunnel
*****

Reged: 11/01/05

Loc: 53 miles west of Venus
Re: Top Opticians in the US for reflectors new [Re: Darren Drake]
      #5692594 - 02/21/13 11:56 AM

Quote:

The book Bonandrini mentioned here a few years ago has apparently been mothballed or seriously delayed.




The so-called book, as well as a lot of other stuff Bonandrini claimed, is
about as real as Manti Teo's dead girlfriend.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Doug Culbertson
Post Laureate
*****

Reged: 01/06/05

Re: Top Opticians in the US for reflectors new [Re: EJN]
      #5692629 - 02/21/13 12:16 PM

Quote:

Quote:

The book Bonandrini mentioned here a few years ago has apparently been mothballed or seriously delayed.




The so-called book, as well as a lot of other stuff Bonandrini claimed, is
about as real as Manti Teo's dead girlfriend.




Careful. I got a similar post removed from the OTO for stating something very similar regarding David B's now mythical book.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mike Lockwood
Vendor, Lockwood Custom Optics
*****

Reged: 10/01/07

Loc: Usually in my optical shop
Re: Top Opticians in the US for reflectors new [Re: jpcannavo]
      #5692749 - 02/21/13 01:17 PM

Quote:

And there is another force that might be at wok here as well. If one were to get a lemon from one of the "real big names", there may be fear that publicizing it, on a forum such as this, would rattle "cherished beliefs" and be taken as somehow being politically incorrect, possibly generating hostile responses.



I can't say why people don't usually speak up, but one very real risk is that the user/client/buyer might be wrong. Mirror testing is not easy, and when you put it in a telescope, the number of variables involved goes up dramatically. It takes experience to determine what the real problem is.

Many issues with mirror cells and other telescope problems have been blamed on the optics, and many true optical problems have been blamed on mirror cell and other issues. Many owners of telescopes blame seeing or equilibration for poor image quality simply because they believe it can't possibly be an optical problem. In reality, it can be.

This is why I advocate that those who aren't expert testers, but still care about optical quality, go to star parties, walk around, and use different instruments over the course of a night. This allows time for optics to cool off. Learn what poor collimation looks like, and learn to recognize it and other issues in images so you don't blame the optics for it. Take notes, including eyepieces used, and see what instruments really perform best at high power.

In short, do your own research, and don't believe everything you hear or read. A trip to a far-away star party may be expensive, but it is less expensive than the loss one might take on a telescope that doesn't perform.

Quote:

What we really need is some organized body of objective consumer reporting.



Aside from the risk of being sued for libel even if the test report is honest and correct (a risk that is greatly reduced by the tester being located in another country!), another risk is that the third party tester/reporter might make a mistake. While some do great work, others might not, and the risk of inaccurate test results goes up dramatically as the size of the mirror increases. If the tester doesn't do it full-time, he/she may be more likely to make a mistake than a professional optician.

Quote:

Given our intense focus (!) on optical quality, it is indeed strange that very little of this actually happens. This absence is even evident in our forums. While they do have review sections, look at the categories. There is no specific section dedicated to reports on mirrors.



The explanation is simple - it is difficult to test mirrors, and any bad report will be countered by a glowing report. Then it turns into a *BLEEP* contest, rather than a discussion.


Post Extras: Print Post   Remind Me!   Notify Moderator  
ml96737
member
*****

Reged: 02/10/12

Loc: Big Island, Hawaii
Re: Top Opticians in the US for reflectors new [Re: Mike B]
      #5692984 - 02/21/13 03:49 PM

Quote:

Quote:

...and John Hall of Pegasus produced several bad ones



I'm not a Pegasus "fan", and have never had one of his optics... i am unfamiliar with the backstory of the circumstances you've described. But i *do* note that the date on the forum notes you linked is over five years old.

These discussions of this mirror maker & that can sometimes turn ugly, and frequently sad stories get trotted out and re-aired. My concern here is that an event from five years ago, or ten years ago, etc. seems to NEVER be forgotten- the maker of a poor, or even less-good mirror seems to be forever haunted- even tho perhaps they have made dozens & dozens of perfectly fine optics, before, and since.

I would not wish such a standard be applied to myself or my work, which is no more or less "perfect" than anyone else's... nor would anyone wish to be pummeled unendingly with their past deviations from perfection.

Just sayin'... Be careful what allegations we toss about... be careful what tossed-about allegations we believe...




These are not allegations, but facts. 3 Pegasus mirrors were tested by interferometry by Mr. Rohr, and were found to be unsatisfactory.

But, the real issue is not so much the bad mirrors, but the fact John Hall guaranteed these mirrors to be "1/10 wave". When in fact they were below 0.80 Strehl! And, when this was brought to his attention, he attempted to cover it up and threaten the evaluator!

Now, maybe in the past 5 years Mr. Hall has completely changed his methods of mirror making, and his attitudes, but then on the other hand human nature is what it is...

As a followup to this whole issue of "bad mirrors" getting out, it strikes me as very poor QC, that very few mirror makers take the small extra effort to star test their "finished" product before sending it out? It would takes just a few minutes to do a careful star test, and that would reveal any of these problems mentioned. This lack of proper final testing of optics is the root cause of quality problems.

It could be so easily avoided at very little cost of time or equipment!


Post Extras: Print Post   Remind Me!   Notify Moderator  
Calypte
Pooh-Bah


Reged: 03/20/07

Loc: Anza, California
Re: Top Opticians in the US for reflectors new [Re: ml96737]
      #5693144 - 02/21/13 05:05 PM

Quote:

As a followup to this whole issue of "bad mirrors" getting out, it strikes me as very poor QC, that very few mirror makers take the small extra effort to star test their "finished" product before sending it out? It would takes just a few minutes to do a careful star test, and that would reveal any of these problems mentioned. This lack of proper final testing of optics is the root cause of quality problems.

It could be so easily avoided at very little cost of time or equipment!



This post is oblivious to the realities of commercial mirror-making. I have no opinion about the alleged fault-free excellence of Zambuto or the claimed failures of Pegasus, since, to my knowledge, I've never seen an example of either. But what this post expects is that the mirror-maker already owns a scope of every possible configuration, every mirror-cell size and focal length, so he can star-test every possible permutation of a completed mirror within the size range he chooses to produce. And "just a few minutes" to mount up each mirror for star-testing? How long does it take the person making this demand to remove a previous mirror from a scope, then mount a new mirror and collimate the scope, then wait for a clear night of good seeing? Possibly a mirror-maker could limit their available product to a selection of a very few apertures and focal lengths. A friend of mine makes batches of dozens of 6s, 8s, 10s and 12.5s for a famous supplier of optical products. He also usually has at least one or two 17.5 or larger mirrors in the shop, often of very short focal lengths, often for reworking from someone else's product. I've seen several of these in his shop for eventual mounting in high-end astrographs made by famous manufacturers (they usually don't make their own optics). To mount up each mirror in a scope designed to accommodate each is simply impractical. Refractor manufacturers can star-test every single scope, but they are testing completed scopes (just put it on a mount and see what it does), and some of the old-time reflector makers star-tested each scope. Again, they were testing completed scopes. Even so, apparently a few bad scopes were shipped. The airy expectations of this post are precisely why my friend abandoned most of the amateur market. He tests his mirrors with interferometry, and he supplies a report and interferogram. I've seen testimonials to the excellence of his mirrors in this forum, and I have little doubt that some of the other mirror-makers cited in these posts can provide equivalent quality. But if Zambuto, Swayze, Royce, et al, want the low-end market, they can have it! My friend views that market as a cesspool of unrealistic demands and a path to poverty.


Post Extras: Print Post   Remind Me!   Notify Moderator  
ml96737
member
*****

Reged: 02/10/12

Loc: Big Island, Hawaii
Re: Top Opticians in the US for reflectors new [Re: Calypte]
      #5693263 - 02/21/13 06:07 PM

Quote:

Quote:

As a followup to this whole issue of "bad mirrors" getting out, it strikes me as very poor QC, that very few mirror makers take the small extra effort to star test their "finished" product before sending it out? It would takes just a few minutes to do a careful star test, and that would reveal any of these problems mentioned. This lack of proper final testing of optics is the root cause of quality problems.

It could be so easily avoided at very little cost of time or equipment!



This post is oblivious to the realities of commercial mirror-making.

But what this post expects is that the mirror-maker already owns a scope of every possible configuration, every mirror-cell size and focal length, so he can star-test every possible permutation of a completed mirror within the size range he chooses to produce.

The airy expectations of this post are precisely why my friend abandoned most of the amateur market....My friend views that market as a cesspool of unrealistic demands and a path to poverty.




With all due respect sir, making an adjustable star testing apparatus for a wide range of mirrors is not difficult at all. Basically, a fixture that can take the size and FL range the maker produces, with a few high quality secondaries and eyepieces. The costs of such simple testing system is a fraction of what it costs to put together a professional optical shop. If you doubt it can be done, then contact Mr. Kennedy. http://www.kennedy-optics.com/process.htm He can explain how he star tests each mirror and makes a profit doing it too!

Reading between the lines here, it appears the real issue is the fear that many professional opticians have of the accuracy and sensitivity of the star test. Better to just finish it up to the level you are familiar with, ship it out with a "certificate", and go do the next one, right?

Also, I get the impression you are implying the standards of the amateur community are too high, above that of the professionals, and are unrealistic? That may be partially true, and my knowledge of several professionally acquired and produced mirrors substantiates that. Eg. Maria Mitchell Obs has one with a bad turned edge, as does the 30" at Lowell Obs. The McDonald 82-inch was 1 wave or worse until Texereau refigured it... The list is quite long.

Zambuto makes mirrors for everyone, and he doesn't ship it until its essentially perfect. He does a large number of mirrors and has no "lemons". If ever a customer wasn't satisfied, he will fix the problem. No if, ands, or buts.

That's quality, service, professionalism, as it should be, IMHO. The rest is just excuses.

Mike


Post Extras: Print Post   Remind Me!   Notify Moderator  
mark cowan
Vendor (Veritas Optics)
*****

Reged: 06/03/05

Loc: salem, OR
Re: Top Opticians in the US for reflectors new [Re: Calypte]
      #5693276 - 02/21/13 06:14 PM

Quote:

My friend views that market as a cesspool of unrealistic demands and a path to poverty.




I knew there had to be something I really liked about this business...

Best,
Mark


Post Extras: Print Post   Remind Me!   Notify Moderator  
Calypte
Pooh-Bah


Reged: 03/20/07

Loc: Anza, California
Re: Top Opticians in the US for reflectors new [Re: ml96737]
      #5693339 - 02/21/13 07:06 PM

Quote:

Also, I get the impression you are implying the standards of the amateur community are too high, above that of the professionals, and are unrealistic?



"Too high" at a price most are willing to pay. "I want 1/20 wave accuracy, peak-to-valley. Oh, I won't pay more than I would for a GSO." My friend says he gets frequent queries like this. Inevitably, they cite a wave-accuracy from some other optician's website. If they can do better with Zambuto, etc., then more power to them. The comparison to Steve Kennedy is interesting, since my friend -- who knows Kennedy very well and has done much business with him -- has his own stories about Mr. Kennedy's quality. But I don't have the story first-hand, and I've personally met Steve Kennedy only very briefly. WRT to the "star test," I thought you might mean with a real star. Again, I think you are not well-informed about the realities of the business, and I'm betting Zambuto & Kennedy would agree!

Edited by Calypte (02/21/13 07:10 PM)


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: Top Opticians in the US for reflectors new [Re: Calypte]
      #5693479 - 02/21/13 08:18 PM

Quote:

...another risk is that the third party tester/reporter might make a mistake. While some do great work, others might not, and the risk of inaccurate test results goes up dramatically as the size of the mirror increases. If the tester doesn't do it full-time, he/she may be more likely to make a mistake than a professional optician....

The explanation is simple - it is difficult to test mirrors




It is interesting that Mike L would make this comment at THIS point in the thread... i doubt we'll hear a more concise AND accurate appraisal on the matter.

Some Dob makers *do* test THE actual optic of each scope in THE actual structure wherein it will reside when shipped to its customer. Such tests can even be done prior to coating. However, some don't test in the scope, anyway... you'll receive the structure from ONE source, and the optic from another. They're *ALL* tested as they're produced- many times thru the process, and presumably when finished- in some manner or another. Yet each method of testing has its value... & its limits.

Makers of BOTH types have good reputations, on the whole. Yet as there is in just about any market, there are stand-outs. I know which i'd prefer myself, if i were plunkin' down the payola. Even so, the Dob i use now was acquired "used"... i have no idea how Starsplitter handled the "testing" when the scopes were shipped to the original owners. But i'm confident this one's (OMI) optics are pretty darned good- based on a LOT of scopes i've owned & used & viewed thru over the years.

Should i have turned down the purchase of this Dob simply because OMI has turned out some poor optics in the past? That's a personal decision each buyer would have to make. I'm glad i did *NOT* turn it down! Should i have insisted on "star-testing" the scope prior to signing over the dough?... just to make sure it was a "good one"? Sure, not a bad idea. But i didn't- went ahead on reputation alone... was a daylight transaction!

I can see from both sides of this... from a buyer's perspective, it's not totally clean-cut. Having mirrors tested & the results made public seems a great idea... one who's execution is swamped with devilish details.

Quote:

But, the real issue is not so much the bad mirrors, but the fact John Hall guaranteed these mirrors to be "1/10 wave". When in fact they were below 0.80 Strehl! And, when this was brought to his attention, he attempted to cover it up and threaten the evaluator!



First, 0.80 Strehl is in NO way a "bad mirror"! It may not be "1/10" wave, if that what was being promised. Assuming that's not a 1/10 wave surface, right?

Secondly, you're assuming the tester is entirely correct, and the manuf. is entirely incorrect. Realities are seldom this clear. Add to this that the story is now how many hands old? I'm presuming these three mirrors were not yours.

Additionally, if Mr. Hall truly felt he was being unfairly charged, and his business rep impugned, does he not have the right to defend himself? Does acting in defense amount to some kinda admission of guilt? Do you see how this can appear? We do not know the *true* backstory on this, and unless we were directly involved, how are we to know whether the actions & statements were noble or deceitful?

I, for one, doubt we can or will know... which is why i cringe at these things being brought up all the time. In fact, (as i understand it) CN's T.O.S. stipulates that posters are constrained to speak only of criticisms regarding their own, personal dealings with any specific vendor. And really, the intent is to work things out WITH such a vendor- definitely *NOT* bash them, and certainly not bash them over dated & second-hand info!

Quote:

Now, maybe in the past 5 years Mr. Hall has completely changed his methods of mirror making, and his attitudes, but then on the other hand human nature is what it is...



Oh, so in the minds of some, he'll be forever suspect. I guess that, too, is an attitude, isn't it?

As i stated before, let's all hope such "standards" & "criticisms" are never leveled at the rest of us & our imperfect work, or even our work imperfectly appraised, lest we, too, never recover... remaining tarnished of reputation the rest of our days.


Post Extras: Print Post   Remind Me!   Notify Moderator  
ml96737
member
*****

Reged: 02/10/12

Loc: Big Island, Hawaii
Re: Top Opticians in the US for reflectors new [Re: Mike B]
      #5693579 - 02/21/13 09:12 PM

Quote:

Quote:

...another risk is that the third party tester/reporter might make a mistake. While some do great work, others might not, and the risk of inaccurate test results goes up dramatically as the size of the mirror increases. If the tester doesn't do it full-time, he/she may be more likely to make a mistake than a professional optician....

The explanation is simple - it is difficult to test mirrors




i have no idea how Starsplitter handled the "testing" when the scopes were shipped to the original owners.




Why depend on others to test your mirror? In fact star testing is EASY. Compared to what it takes to do accurate bench testing to 1/10 wave, or the complexities of phase shift interferometry, star testing is Trivial

In fact, everyone who buys a mirror should also get Suiter's book on star testing with it, so there is no question about the actual quality of the optic in anyone's mind.

Quote:

Quote:

But, the real issue is not so much the bad mirrors, but the fact John Hall guaranteed these mirrors to be "1/10 wave". When in fact they were below 0.80 Strehl! And, when this was brought to his attention, he attempted to cover it up and threaten the evaluator!




First, 0.80 Strehl is in NO way a "bad mirror"! It may not be "1/10" wave, if that what was being promised. Assuming that's not a 1/10 wave surface, right?




No, Pegasus own website says their guarantee is 1/10 wavefront P-V, 1/36 wave RMS, Strehl 0.97, but interferometrically measured was Strehl 0.78

Quote:

Secondly, you're assuming the tester is entirely correct, and the manuf. is entirely incorrect. Realities are seldom this clear. Add to this that the story is now how many hands old? I'm presuming these three mirrors were not yours.




No, this is first hand from Rohr's public website.

Quote:

Additionally, if Mr. Hall truly felt he was being unfairly charged, and his business rep impugned, does he not have the right to defend himself? Does acting in defense amount to some kinda admission of guilt? Do you see how this can appear? We do not know the *true* backstory on this, and unless we were directly involved, how are we to know whether the actions & statements were noble or deceitful?




No, he was being fairly charged for falsely advertising his products, and failing to correct the deficiency. Rohr has no motive to falsely evaluate Pegasus products. You can compare to Rohr's evaluation of Zambuto mirrors by the same criteria, he shows they are practically perfect as they star test too.

Quote:

...definitely *NOT* bash them, and certainly not bash them over dated & second-hand info!




Telling the truth is not bashing, heresay, or libel, its the truth.


Post Extras: Print Post   Remind Me!   Notify Moderator  
auriga
Pooh-Bah


Reged: 03/02/06

Re: Top Opticians in the US for reflectors new [Re: ausastronomer]
      #5693736 - 02/21/13 10:59 PM

Quote:

Hi Pete,

Maurizio Di Sciullo used to sell his scopes under the name of Excelsior Optics. These were designed as specialist long focus tubed planetary newtonians, either F6 of F8. To my knowledge Maurizio hasn't produced a scope or mirror in about 10 years, due partly I believe to poor health. If you can find one second hand they are outstanding. Similalrly Peter Ceravolo hasn't built an amateur scope in about the same time period, concentrating on scientific and Government type work over the past 10 years. If you can find one of his second hand they are outstanding.

The other 3 all have excellent reputations. Along with Mark Suchting in Australia these are the only people I would consider buying my next mirror from, if I ever have a need to buy one. I have eliminated OMI on the basis that they only work with 2" thick glass substrate, which doesn't suit me or my scope design parameters. In the future moving forward I will only ever order a mirror made from minimum thickness substrate in the interests of fast cooling. In smaller slower apertures I would also consider people like Gordon Waite, Alan Raycraft, Dick Wessling and a few others.

Cheers,




Dick Wessling made fine short focus mirrors, I have one of his 16" f/4 mirrors which is superb. But alas, Dick passed away three years ago.
Auriga


Post Extras: Print Post   Remind Me!   Notify Moderator  
Calypte
Pooh-Bah


Reged: 03/20/07

Loc: Anza, California
Re: Top Opticians in the US for reflectors new [Re: auriga]
      #5693787 - 02/21/13 11:44 PM

I asked my mirror-making friend about star-testing. He does star test with a point-source. He performs this test for astigmatism.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | 5 | 6 | (show all)


Extra information
7 registered and 21 anonymous users are browsing this forum.

Moderator:  ausastronomer, Phillip Creed, JayinUT, okieav8r 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 5658

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics