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A Scope for the Ages or Just Aging?

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#76 Brian L

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Posted 19 May 2010 - 12:24 PM

It's easy to speculate that Questar has some magical formula for coatings that is superior to all others. It's also easy to say hogwash and chalk it up to Questar mysticism. The reality is likely somewhere in between. It's not as complicated a process as they would like you to think, but it is also more involved than what you get with Meade UHTC and Celestron XLT coatings.

There's more to this story than I am willing to publicly disclose at this point. Who knows....someday I might write a CN expose piece.

#77 astro_que

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Posted 19 May 2010 - 12:56 PM

It's easy to speculate that Questar has some magical formula for coatings that is superior to all others.


Brian, I made no such speculation about magical coatings. As far as I know, they do not use the Lawrence Livermore encapsulated process. I provided information about the wide variety of coatings that exist. Questar made no statement to me about the complexity of the process. Questar doesn't coat; they send out to a lab

#78 Clive Gibbons

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Posted 19 May 2010 - 01:27 PM

Robert,

didn't you mention Perkin-Elmer as being the coater for your older BB Questar?
At least, that's what Jim R. said when he saw your scope.

#79 astro_que

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Posted 19 May 2010 - 01:56 PM

Clive, actually, it was the newer Questar, the '81, that Jim identified as having a Perkin-Elmer coat. Interestingly, the '76 seems to have less reflection intensity off the corrector. The '81 has a strong violet reflection, while the '76 has a subdued shade of green as one would expect with a modern optic. One may surmise that they switched for a reason. Durability?

I've been looking at local coatings companies. I have a call into one for general information. There are two companies local to Questar and me, though I have no idea whether they use them. I have seen two reflectivities attributed to Questar BB mirrors. One is extremely high: 99.9%. Such a coating is offered by ECI here in Willow Grove: http://www.evaporate...r/print/109.htm
Another coating, more compliant with what Jim told me in a recent conversation, is offered by Acton, a division of Princeton Instruments, the makers of the CCD cameras: http://www.princeton...ing_Rev A1.pdf.

Back in the days of yore, an amateur astronomer silvered his mirror in the bathroom with silver nitrate. The main danger was that of explosion of the concentrated nitrate. The coating might last six months. Today, it is a much more complex process. There are binder layers, there is the silver, there is the tuned dielectric overcoat, and there is the protective layer.

Today, pure dielectric coatings, made of 40 or more alternating layers of two or more materials with different indices of refraction, are advocated for durability. Opticians refer to each layer as an "etalon", the French word for gauge. Each alternating layer achieves total internal reflection for a specific band of wavelength. However, because these coatings are so thick, they actually change the figure of the mirror. Also, Jim explained to me that all their scopes both commercial and military, are optically identical. There is a strong need in government for high IR reflectivity. Dielectric coatings cannot be tuned to function over a sufficiently wide bandwidth.

The dielectric enhanced silvered mirror consists of binder layers, the silver layer, which may be encapsulated, and several etalons made of different materials for enhancement. These days, this ensemble is overcoated with silicon dioxide. The advancement in the past ten years has been extraoardinary. Perhaps some day, the Lawrence Livermore process will become feasible for small mirrors. It is simply too labor intensive at present.

#80 Clive Gibbons

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Posted 19 May 2010 - 02:34 PM

Seems that at this point, we don't know who does the BB coating for Questar.
We don't know the exact configuration of the coating.

We do know that it's warranted for 5 years and that applies to the original owner.
Many folks who own BB coated Q's report great longevity.
Some folks haven't been as fortunate.

Not much else to say, re. coatings, IMO.

Over 'n' out. :salute:

#81 Rat8bug

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Posted 19 May 2010 - 03:01 PM

Are you speaking of the Perkin Elmer that screwed up the Hubble ST some years back? I'd be scared :lol:


Robert,

didn't you mention Perkin-Elmer as being the coater for your older BB Questar?
At least, that's what Jim R. said when he saw your scope.



#82 Frank2

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Posted 19 May 2010 - 03:50 PM

I am the original poster of this thread and it was my intention to offer an observation about the current state of Questar and make no further comment, however, before this thread goes completely off topic let me add the following: I feel safe in saying that we all want the same from Questar, the best production telescope in the world, period. The truth is that Questar has met that criterion in an increasingly narrow sense since its introduction. We are now left with arguing that the telescope has superior optics and excellent machining of the mount components. In almost every other respect the Q is now inferior to other serious telescopes. If anyone doubts the longing for Questar to resurrect the brand just look at the post with the most hits in this forum and you will see that Q owners are trying to do for themselves that which Questar will not.

Frank

#83 astro_que

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Posted 19 May 2010 - 04:02 PM

Are you speaking of the Perkin Elmer that screwed up the Hubble ST some years back? I'd be scared :lol:


It was indeed. I know you're joking, but for those who don't know, Perkin Elmer was the premier maker of advanced optics in the U.S. The Wikipedia article doesn't state, but I believe they divested that business to concentrate on life sciences. It seems true that Perkin-Elmer bungled the Hubble job, but other than that, their optical reputation was of very high esteem.

#84 akman1955

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Posted 19 May 2010 - 09:30 PM

Clive, does all this mean that the older bb coating were done better and last longer? due too coater or process? as time has passed and they are still good. john

#85 astro_que

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Posted 19 May 2010 - 09:56 PM

In theory at least, the older coatings did not last as long, because they were based on thorium fluoride. In fact, Questar reports fewer coating failures with the newer coatings.

#86 Clive Gibbons

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Posted 20 May 2010 - 07:42 AM

Clive, does all this mean that the older bb coating were done better and last longer? due too coater or process? as time has passed and they are still good. john


Hi John.

I don't have info to make an informed comment on that, one way or the other.
Hard to say if anybody, other than a Q insider with actual data, could answer the question.

In an earlier posting, Robert recounted something said by Jim R. at Questar.
"As far as Jim Reichart's opinion about age, and the effect on coatings, when I spoke with him, he was unconcerned. Most of the scopes he sees from that era are just fine. A decade is the absolute minimum of durability, when stored in less than optimal conditions."
That was in reference to BB coatings from the mid '70s to early '80s.

#87 akman1955

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Posted 20 May 2010 - 08:16 AM

:)Thanks All! If my coatings ever fail i would still keep it as a "work of art" sitting on bookshelve or spare parts for another one. john

#88 akman1955

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Posted 20 May 2010 - 11:10 PM

:)Clive, i liked the funny hat guy as your avatar and the cute kitten..we all know life is a pain.. :grin: :lol: :tonofbricks:as we are not getting out of it alive. :help: :lol:,john

#89 Matt Looby

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Posted 26 May 2010 - 08:01 PM

Go-To? I watched a fellow with one of those scopes... he could not get the scope to slew to Jupiter... what a pitiful sight. I could make this a long story...
but hey what's the point?

I use the Questar setting circles to locate hard-to-find DSOs... (I live under real dark
sky... the finder is more than adequate...) with my "old fashioned" chart
I can dial onto the ONE or TWO objects I wish to OBSERVE in a SESSION,,
Easy-peasy-lemon-squeezy LOL!!!!

#90 trainsktg

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Posted 14 June 2010 - 05:44 PM

So...a fellow starts a post in aficionado forum with "why is it so difficult for Questar owners to see the obvious?" I applaud the responding Questar owners for their patience, civility and continuing good manners in spite of the not so subtle evaluation of their combined intellect.

Keith

#91 Les

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Posted 15 June 2010 - 04:05 PM

It's so much easier to be patient and civil when you're the one owning the Questar. :grin:

#92 Rick Woods

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Posted 16 June 2010 - 08:07 AM

It's so much easier to be patient and civil when you're the one owning the Questar. :grin:

Which, if I'm not mistaken, Keith is? :D

#93 Rick Woods

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Posted 16 June 2010 - 08:16 AM

I'm a little late coming in here, and I haven't read all the posts; but let me throw in my two cents:
I dream of someday having a Q7. No way I could even think about it right now, but everything changes. I don't think I could justify a Q90, it's just too small to suit my needs. But a Q7 - now, there's a dream scope for a planetary observer like me. I've never looked through one, but that's only one of many things I haven't tried, but I know I'd like. (TOS prohibits naming some of the others).

#94 trainsktg

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Posted 16 June 2010 - 10:34 AM

It's so much easier to be patient and civil when you're the one owning the Questar. :grin:


Excellent point :lol: .

Which, if I'm not mistaken, Keith is? :D


Well, (very) soon to be (mere days away in fact :jump: ) .

BTW, hello again Rick, after my long absence :) .

Keith

#95 Rick Woods

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Posted 16 June 2010 - 11:20 AM

It's so much easier to be patient and civil when you're the one owning the Questar. :grin:


Excellent point :lol: .

Which, if I'm not mistaken, Keith is? :D


Well, (very) soon to be (mere days away in fact :jump: ) .

BTW, hello again Rick, after my long absence :) .

Keith

Hello again to you too, Keith, and a hearty woohoo! for your impending delivery!

#96 Les

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Posted 16 June 2010 - 05:18 PM

Hi Rick,

Every argument made here against the Q3.5 can certainly be made against the Q7. I even had one prominent local dealer in MD try to talk me out of the purchase. But it was one I could afford and never regretted. I am more than happy that I parted company with my IM603 Mak-Cass.

#97 peashooter1982

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Posted 19 October 2013 - 12:58 PM

For $4000 I can get an 120MM EON


Out of curiosity I looked this up. It was made by Orion and on their website it says "Not Available; This product is no longer available for purchase."

Perhaps a case of Survival of the Fittest.

#98 munirocks

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Posted 21 October 2013 - 06:40 PM

Computers come and go. Setting circles go on forever. I don't see the advantage of putting "M27" into a control panel, over dialing M27's coords into setting circles. The circles will keep working for the next 100 years. I'll get the coords from a revolving door of various replaceable computer systems and smartphones over the years. So I essentially have a computer-controlled system with a modular, replaceable computer. It's future-proof and indestructible. And after working with computers all day in my job, the elegant simplicity of setting circles is like a breath of fresh air.

#99 Erik Bakker

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Posted 21 October 2013 - 08:53 PM

Computers come and go. Setting circles go on forever.... It's future-proof and indestructible. And after working with computers all day in my job, the elegant simplicity of setting circles is like a breath of fresh air.


+1 :waytogo:

#100 starboy1954

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Posted 24 October 2013 - 04:09 PM

Computers come and go. Setting circles go on forever.


Great line.

Setting circles have an organic connection to the heavens and when I use them I am part of that.

And the aesthetic pleasure derived from rotating the Questar dials is an experience not afforded by button pushing.






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