[ATM] The 16 inch Ultrathin ronchi pics

[vorblesnak <vorblesnak@peak.org>]

Steve Koehler wrote ..

> David,

> These are nice Ronchi images, and show a lot.  I agree that the line
> leaning is clear in your comparison image.

> I'm still curious what you intend to do about getting the correction
> closer.  Do you see the evidence in the Ronchi images of
> undercorrection?  If you figure from Ronchi, how do you intend to

In image one and two I see a central hump that extends out the 50% / 60%
zone.  This seems to be supported by the lines shown in the line of four
on the last set of images.  That kink is an obvious zonal error.  The 
lines are about the same width though so the ROC between the zones is
very close.

> measure the correction to address that problem?  From Dale's analysis,
> the correction error is several times more objectionable than the
> astigmatism.  I wouldn't worry about the astigmatism too much until
> that  is brought under control.

The problem is two fold.  What is causing the astigmatism and what is 
causing the false positive.  Heat could be at the root of both.  I am 
working on two pie plates right now attempting to replicate the error
that is in the 16.  I have caused astigmatism in the one.  It increased
as I moved closer to correction, decreased as I polished back towards
a sphere.  At this point I cannot discount anything.  I am considering
working in water to add mass to pull off the heat.  I will take what I
learn from the pie plates and use it on the 15.5.  I probably won't 
touch the 16 for a month or better so no need for a comparative ronchi
just yet. 

> If it seems useful, I will run 50 lpi Ronchi simulations with your
> mirror and with a perfect f/3.5 for comparison.  I won't be able to
> get to this until Monday, however.
> --
> Steve Koehler

David Davis
Toledo, OR 97391

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