Re: [ATM] Aplanatic Schmidt-Cassegrains with aspherical mirrors

["matt" <mariusrf@bellsouth.net>]

There is no need for curved CCD chips.
Technology exists, based on coherent fiberoptic plates ,that allows such
curvature to be easily corrected . This technology is used for image
intensifier tubes , scientific CCD , etc.
True, it is expensive , but such devices can be had surplus for pocket
change. Here's one:
http://www.surplusshed.com/pages/item/l3172.html

best regards,
matt tudor

----- Original Message -----
From: "Dominic-Luc Webb" <dlwebb@canit.se>
To: "Scott Ewart" <scott.e@quicksurfer.com>
Cc: <atm@atmlist.net>
Sent: Wednesday, January 12, 2005 3:08 PM
Subject: Re: [ATM] Aplanatic Schmidt-Cassegrains with aspherical mirrors


>
> On Wed, 12 Jan 2005, Scott Ewart wrote:
>
> >     Could the corrector in any way help correct field curvature by
enabling
> > a flatter curve somewhere else?  It doesn't sound like it.  It seems to
me
> > that's the one and only strike against an RC designed for photography
for
> > the masses.  What good are pin-point stars at the corner of the field if
you
> > can't focus on them, at least not without another corrector?  Unless
they're
> > coming out with a new curved ccd chip:)
> >
> > Scott
>
>
> I would bet they are thinking more and more about this. My novice mind
> thought of this long ago, and I even posted some comments about curved
> CCDs long ago (years). That being said, consider the case for film
> placed on a curved surface perfectly matched to the curvature at focus.
> Having made these correctors, two interesting observations emerged.
> First, the curvature is very slight. Second, the film is very thick.
> One reaches a point in which it could be discussed where within the
> thickness of the film one wants to focus. Before you go rushing off to
> make a curved CCD or a curved film plate, see what is managable with a
> flat surface. Most of the systems people in here are discussing end up
> with only slightly curved focal surfaces, although, I have not been
> following this thread to know the details of any specific design. I
> suspect any transmission type corrector you try to make/add to this
> system will add aberrations and you'll end up accepting the curved
> surface as is.
>
> Dominic-Luc Webb
>
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>

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