From: "Richard Schwartz" 
To: 
Reply-To: "Richard Schwartz" 


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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