The relative merit of the tests can be debated and debated, but in my mind
it really doesn't address the real question. To me the question is what
should be expected when I spend the extra money for a "premium"
mirror. Since it seems that these are the only numbers we are getting it
would be nice if they could add up to something useful that we could use in
determining if a mirror is "premium" or not.
So if you ever figure this out I would appreciate hearing about it.
Sincerely,
Derek
At 02:43 PM 11/29/00 -0800, you wrote:
>I remember that article, but I don't remember where I saw it. I think there
>were multiple observers, one of which was Terrence Dickinson. That would be
>the Canadian book writer.
>
>It seems to me that it would be at least as difficult to tell a 1 wave from
>2/5 wave in a 24" mirror as it would be to tell 1/4 from 1/10 in a 6".
>Unless diffraction was the main limiting factor in the 6" scopes (which I
>guess is the case, now that I think about it).
>
>Jon.
>
>----- Original Message -----
>From: Jim Van Nuland <jvn@No-Spam>
>To: <sf-bay-tac@No-Spam>
>Sent: Wednesday, November 29, 1999 1:39 PM
>Subject: interferogram test results Strehl ratio .9-.95(90-95%
>ofperfection)
>
>
> > Several years ago, Peter Ceravolo made some 6 inch f/8 scopes of
> > known 1/10, 1/4, 1/2, and 1 wave error, with very smooooth
> > surfaces. An expert planetary observer had considerable trouble
> > telling the 1/10 from the 1/4. During periods of perfect seeing,
> > it took him multiple compares to be certain.
> >
> > Forgive me for not remembering the name of the observer. I think
> > he lived in Canada. He's written at least one book.
> >
> > -- Jim Van Nuland, San Jose (California) Astronomical Association
> >
> > On Tue, 28 Nov 1999, Paul LeFevre wrote:
> >
> > [big snip]
> >
> > > One thing Jon -- you're very unlikely to see the difference between 1/15
>and
> > > 1/20 wave EVER while observing...the seeing usually limits you to MUCH
>less
> > > resolution than either of those values could give you :)
> > >
> > > Good luck,
> > > Paul
> >
> >