From: "mommoteandcoyote" 
To: "George Anderson" 
Cc: 
Reply-To: "mommoteandcoyote" 


George,

HEAR, HEAR! or is that, HERE, HERE!!! Well, in either case, well spoken! 
Then, we can speak of the venerable Snider-Enfield

Coyot‚
----- Original Message -----
From: "George Anderson" 
To: "Richard Schwartz" 
Cc: 
Sent: Thursday, January 23, 2003 8:14 PM Subject: Re: ATM An Old TMs Simple Query


>
> Believers in Schmidt's should have a read of Robert Reeves "Widefield
> Astro-Photography".
> You will mortgage your paid off house and sell your first born after you
> are infected with Schmidt envy.
>
> George Anderson
> Montreal Canada
>
> Clear skies and good health
>
> Richard Schwartz wrote:
> >
> > OK, I have a few schmidt questions...
> >
> > If I have a schmidt, I will end up with a lot of little round pieces of
> > film.  What is a good way to cut the film to the requires shape and
size?
> > What is a good way to identify the films, index them, and store them?
What
> > is a good way to take measurements off of them?  What is a good way to
warp
> > the film to match the curved focal plane?   If a field flattener lens is
> > used, what is a good way to remove distortion from the image, and to
correct
> > measurements on the distorted image (assuming the exact center of the
image
> > is not located).
> >
> > I think the science value is greatly enhanced when the images can be
located
> > in time and space, and stored in a non-destructive way.   There is more
to
> > working with schmidts than just building the optics.
> >
> > What I really would like is (1) some kind of field flattener lens, and
(2)
> > something like a Hasselblad camera back that automatically records date,
> > time, and approximate RA and Dec.
> >
> > . . . Richard
> >
> > ----- Original Message -----
> > From: "Jerry Hudson" 
> > To: 
> > Sent: Wednesday, January 22, 2003 11:16 AM
> > Subject: Re:ATM An Old TMs Simple Query
> >
> > >
> > > To ol' Coyote -
> > >
> > > Your formula,
> > > >  a*rho^2+b*rho^+b*rho^4...
> > > giving the shape of the Schmidt plate, is
> > > exactly opposite in sign to the wavefront
> > > aberration describing an uncorrected spherical
> > > mirror.  The glass introduces just enough extra
> > > path length where it is thicker to compensate.
> > >
> > > A straightforward way to see how this all works
> > > out, if you have the patience and either a
> > > good calculator or BASIC, is to start
> > > at the desired focal point of the sphere and
> > > trace a ray, bouncing it off the sphere, and
> > > taking it out to where it intersects a plane
> > > positioned where you want the plate to go.
> > > Figure out the path distance along that ray,
> > > and subtract off the path distance for the
> > > central ray.  THat's your "wavefront aberration."
> > > If you plot this against radial distance of
> > > the ray from the axis, you will get a 4th order
> > > looking curve.
> > >
> > > Note that adding the rho^2 term simply re-focuses
> > > the wavefront - you have this degree of freedom
> > > to try to make the overall power of the plate
> > > to be zero (avoiding all but a trace of color).
> > >
> > > I hope this helps.
> > >
> > > BTW, I'd enjoy a direct off-list exchange with
> > > you about Schmidts - an interest of mine.  I've
> > > only made one: a Wright-type Newtonian.  And, yes,
> > > Edgar Everhart's articles were a great help to me!
> > > He was a smart guy and a great glass-pusher!
> > >
> > > - Jerry Hudson
> > >
> > >
> > >
>
>

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