Re: [ATM] 3 Inch Off Axis Schmidt Camera?

["Bob May" <bobmay@nethere.com>]

----- Original Message -----
From: M/S Heald <maheald@octa4.net.au>
To: <atm@atmlist.net>
Sent: Wednesday, January 19, 2005 2:46 PM
Subject: [ATM] 3 Inch Off Axis Schmidt Camera?


>     Questions:
>
> 1)       What would the image circle of a 75mm Schmidt camera be?  Would
it
> even cover 35mm film?
That depends upon the focal length of the camera and how much bigger the
primary is compared to the corrector for an unobstructed view.
>
> 2)       Would a radius of curvature of the film of about 175mm be too
> severe - would the film crinkle in the holder?
7" ROC is a bit small for even 35mm film I would think.  Make a quick sphere
of that size and see if it fits without problems.
>
> 3)       What would the sky coverage of such a system be?
See question #1.  This is a variation of the same question.
>
> 4)       How close to perpendicular to the light path can the corrector
> plate and film cassette be in order to avoid unacceptable astigmatism?  I
> think I can focus the  primary onto the film well enough, but I haven't
satisfied > myself that I can align the film holder cassette and the
corrector plate to within
> tolerances to avoid  astigmatism.
You don't have to worry about astigmatism so much as focusing the plate.
>
> 5)       Most importantly, is such a system reasonably doable?
With amateurs and our unlimited time, it is doable.  The hardest part will
be doing the corrector plate right.  After that, it depends upon your
machining skills.
>
>     Thank you for your help.  Best regards.
> Mike

Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net


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