RE: [ATM] Re: [atm_free] The zonal Foucault test is freeofinherentcorrection bias - some supporting graphs

["Richard Klappal" <klappal@xnet.com>]

Why doesn't someone who remembers their differential calculus just do a
sensitivity analysis of the ray trace. True "height" of the ray at the
mirrors surface vs. the "height" (radius) of the Couder mask openings and
the sagitta between the Couder mask and the mirrors surface.  Delta height
vs. delta longitudinal aberration, mirror surface RoC vs. Couder mask
distance, etc....

I didn't do well in that math in the first place and it was about 35 years
ago besides, so I don't trust me doing it...

Richard

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net]On Behalf
Of Michael Peck
Sent: Monday, 14 March, 2005 00:06
To: atm@atmlist.net
Subject: Re: [ATM] Re: [atm_free] The zonal Foucault test is
freeofinherent correction bias - some supporting graphs


At 22:55 3/13/05, Ken Lowther wrote:


>>>After your first line, I would vote for impatience
>>>and the inability to
>>>be 100% honest with yourself as being the biggest
>>>errors.  Ken
>>
>>Unfortunately, Science is not a Democratic process.
>>Science requires proofs, not votes.
>
>OK. Poor choice of words but are we now being asked to decide which
>formula prevails and decide which one is right?  Like that ain't voting....

Ken:

Going back to an earlier post of yours, I think the claim that's being made
is that sufficiently large and fast mirrors that test fully corrected in
the Foucault test tend to be systematically undercorrected by as much as
1/4 wave or so in presumably more accurate tests. The definition of "large
and fast" seems to be pretty flexible. Atm_free has had repeated, somewhat
cryptic, posts about a 10" f/5 mirror that I guess some well-known mirror
maker certifies as perfect which might possibly actually fall a little
short of perfection. I wouldn't consider that particularly large and fast,
but I assume that is about the level where systematic effects are presumed
to start appearing. That's conveniently just slightly larger and faster
than any of the round robin mirrors.

With Ken Hunter's comment duly noted (and I agree with it!) I'm inclined to
think you're right about impatience and wishful thinking.

I'm not sure what you mean about deciding "which formula prevails" though.
If you're referring to the choice of effective zone radius that I posted
about earlier today that's a relatively minor issue. It's also one that can
be decided fairly objectively with simulations.

>I'd like to say "What about the Hubble?", but I doubt it was used on that:
>http://yarchive.net/space/optics/hubble.html
>

Thanks for the link. It really would benefit anyone who's interested in HST
optical tests to read the whole thing.

Mike Peck


------
Michael Peck
mpeck1@ix.netcom.com

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