From: "mommoteandcoyote" 
To: 
Reply-To: "mommoteandcoyote" 


Dave,

My browser doesn't seem to want to access your link, I'll try it again later...

  My particular math deficiency, (chuckle), is *not* with the calculations
used to produce the appropriate corrector lens vacuum deformation, nor the
proper tool RC to create the proper neutral zone radius to produce the
proper corrector plate, for any Schmidt optical system, be it a simple, or
a compound, (within the bounds of elasticity). All this is pretty much
"matter of fact", demonstrable stuff, that I've worked with for
years.  I understand it, it is predictable, and repeatable.

No, Dave The problem is a conceptual one. Something I'm not quite grasping.
You know, it's like that tip of the tongue thing,  it's right there but you
just can't get to it.  Richard F.L.R. mentioned Kingslakes book as a
reference that helped him... I've poured over pages 317-320 of that book so
many times the last 20 years, the type is about worn from the pages.

It is SIMPLE. It has to be.  But it has been bugging me for 30 years. I'm
hoping that by posing the question to the folks on the list, that maybe the
discussion will trip the synapse that puts it all together.  Then I'll
know, and you guys will see my red face shining in the night sky all the
way to Denver, that is how SIMPLE it is likely to be.


Coyot‚
----- Original Message -----
From: 
To: 
Sent: Tuesday, January 21, 2003 12:15 PM Subject: Re: ATM An Old TMs Simple Query


>
> Hello ol' Coyote,
>
> I'm not quite sure what you're asking.  Here's a spreadsheet that does the
vacpan calculations for you:
>
> http://members.aol.com/aplanatic/vacpan.xls
>
> The aspheric function, z = a*rho^2 + b*rho^4 + ...
>
> is just a way to describe the surface height (or corrector thickness), z,
as a function of the radial distance from the center of the corrector, rho.
The coefficients, a, b, c,... are selected to make the best corrector
possible for a given optical problem.
>
> 'b' is called the fourth-order coefficient and it (loosely) governs the
amount of spherical aberration that is introduced by the corrector.  This
spherical aberration (SA) cancels the SA introduced by the other optical
components in the system.
>
> 'a' is called the second-order coefficient and it (loosely) governs the
optical power of the corrector.  It is choosen so that the corrector has
minimum chromatic aberration, which typically places the neutral zone at
about 80%.
>
> -Dave-
>
>
>
>
> > I have asked a few of the guys, on the side, this question...Well, now
I'm putting it before the board. (Gulp), Here goes...
> >
> > I have been building small Schmidt systems for many years now,
configured as prime focus cameras, visual Newtonians, and  photo/visual
Cassegrains.   Primarily, I've been using Everhart's variation of
"Grandpa"
Bernard's vacuum pan method for producing the corrector plates, with very
good results.  His math was, and still is, quite easy for me to understand
and relate to the actual physical, quantifiable, and mechanical functions
necessary to produce the desired optical effect upon the system as a whole.
However, in all the years of walkin' around the bench and holding my eye
precariously close to a very sharp object, peering earnestly, hour upon
hour, past a little spot of light, I have never been able to grasp the
basics of the polynomial equations necessary to describe the specific
profile on a specific corrector plate and how it actually relates to the
plate.  You know, the old
> >
> >  a*rho^2+b*rho^+b*rho^4...
> >
> >  The coefficients of the even aspheric I think is what it's called.  How
does this become the 3 expressions that are used  when referring to a
specific plate, AND WHAT ARE *THEY* WITH REFERENCE TO THE PLATE?  Call me
dense... Call me 'tupid... But over my head it goes...     In any case,
these and other related equations plum stump the ol' Coyote.  I can create
the proper curves on the glass at the bench, but I'll be damned if I can
figure it out mathematically so I can enter it
> > into a computer program.  Chuckle, chuckle,
> >  chuckle!
> >
> >  Any help you all can lend would be GREATLY appreciated! "
> >
> >
> >
> > Talk with you soon,
> > Coyot‚
>
>

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