Re: [ATM] Luri-Houghton prescriptions.

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

----- Original Message -----
From: Ukyo Chen <ukyochen888@hotmail.com>
To: <atm@atmlist.net>
Sent: Wednesday, October 12, 2005 10:53 PM
Subject: Re: [ATM] Luri-Houghton prescriptions.


> Bob,
>
> Why not tell us your requirement and we can use software to
help you design.
> I use OSLO and Zemax which are all professional optical
softwares. OSLO is functional better than Zemax.
> What's the Diameter? A:12.5"
12.5: aperture with a 13.75" primary mirror
> What's the F ratio?
F4.6 Focal length is 119"
> What's the diameter obstrution rate you want?
He's planning on a 3.1" secondary and that will be the
obstruction
> What's the extend volume you want from the tub surface to the
focal plane,
> for example you need around 50mm for a camera, or 100mm for a
float focuser,
> or totally 50+100 for them all.
Extend volume is a term that I don't understand but from the
following example you provided, I assume that it is a translation
problem from what Zemax asks for but the focuser will be a 2"
focuser and an unvignetted FOV is what is desired.
> ......
>
> Best Regards,
> Ukyo Chen
>
The thing here is that I've got a prescription that has been
scaled up from the previously built 9.8" scopes that is in the
first posting on this thread and a prescription that I have
generated from TRACE also in that post.  The original
prescription produces a fair bit of negative coma as well as not
being as controlled at the edge for astigmatism as the second
prescription is.
The question is whether I'm close to optimum for mimimal spot
size with the second prescription or is there something else that
can put things closer than what I've gotten.  I'll note that
there is a whole range of approximately similar curves that gets
to about the same level of spot size.  It appears from the work
that I've done is that the null for spot size can be done with a
whole range of curves near what I've done but the bendings of the
lenses does tend to be about the same overall.
Bob May
bobmay at nethere.com
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http: slash /bobmay dot astronomy.net
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Thank you for your understanding!


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