Re: [ATM] Luri-Houghton prescriptions.

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

I'm about to fire up TDesign to verify some of these designs.
The field curvature is unacceptable basically as the focal plane
needs to be flat.  I'd suspect that bending one of tghe lenses or
both of them will give the flat field needed.  I'd also suspect
that the coma thqt I'm seeing in a number of the designs is
removable by a little bit of aspherizing of the primary to
compensate for this.
One thing that I'll note is that for the smaller sized, you can
stand more aberration of the image as the Airy disk isn't as
small as it is in the larger scope.  The errors grow as you
expand the size of the scope while the Airy disk shrinks thus at
some point, you have to start controlling the design better than
the equal curve idea - kind of like going in the refractor design
from the cemented doublet to an air spaced doublet.
I think that I'm also going to have to write a page on the design
of this instrument as it is getting rather involved.
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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