Just an aside--with high end custom optics such as Galaxy, Pegusus, Nova--their quality varies
a good deal although it is generally high. You can even pay extra to get a "pick-of-the-litter"
mirror from them.
I guess the real question is when do you reach a point of diminishing returns??

Andy


> I have some concerns about the optical quality of my 10 inch f/6.3. Bright objects (eg
> Jupiter) have a glowing halo and star test diffraction patterns seem to show spherical
> aberration; a strong outer ring inside focus, and a corresponding shadow outside
> focus.
>
> When these concerns were expressed to John Piper he advised that this was normal and he had
> not seen an SCT with the same pattern inside and outside focus. Are there any f/6.3's out
> there with "diffraction limited" optics as revealed by a star test?
>
> Geoff Todd
>
> John is a good man but he does tend to start every answer with "That's quite normal".
> I can understand that. Picture yourself sitting behind a telephone, the only
> contact in the world for LX200 problems. He has probably heard it all, several
> thousand times over--and--over--and--over!!! The bottom line is that he is right.
> There never was, and never will be, an SCT with the same pattern both inside and
> outside of focus. This is an absolute statment. I can say that I have never seen
> a diamond without flaws. The question is not a qualitative one, but a quantitative
> one. Meade is not prepared to guarentee a research-grade tolerence spread of optical
> performance. As a mass produced item, you will find the optical and mechanical
> tolerance spread is quite wide. Meade does match the primary, secondary
> and corrector lens as a set. They also rotate each of these elements with respect
> to each other to achieve "maximum" image quality for that set of 3 optical surfaces.
> The point I am trying to make is that the "maximum" image quality varies over a
> somewhat wide range between mass-produced optical sets. Hundreds of potential
> customers have called Meade and asked if they could get "the-pick-of-the-litter"
> optics for and additional amount of money, some companies offer this service,
> Meade says NO.
>
> The bottom line is that when you order a mass-produced telescope, you roll the dice.
>
> If your optics are grossly out, then Meade will replace them. If they are inside
> the tolerence limits then the only thing I can suggest is to try collmination (SP)
> or selling the scope on Astromart and rolling the dice again. By the way, an f/6.3
> is a lot harder to figure than an f/10. Is it possible that you are being over
> critical?
>
> Forget the star-test, try this:
>
> Observe Saturn, in good seeing conditions, at about 150 - 250X, if after 5 minutes
> you cannot see Cassini's (SP) division "crisply" then colminate your scope and try
> again. If no joy, return it to Meade as out of tolerance.
>
> Chris Frye
> Silver Spring, MD

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