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ATM Thanks for DK Cassegrain Advise




Thanks all for  your inputs on my proposed 9" F40 Dall-Kirkham project.

Gary & Chuck make a good point in that I should consider other designs
(refractors, Schiefspliegler, etc.). I thought these would be too aperture
limited but as Chuck points out - a 4 incher would not be as atmosphere
limited as my DK Cass. Maybe I should consider two planetary OTAs; a smaller
(more portable) planetary OTA for marginal seeing conditions and the DK Cass
for good seeing conditions. 

I will try to track down the baffle design algorithm in Applied Optics
locally first - thanks for the offer to send it to me Mike. Do you happen to
know how much code is involved and how CPU intensive it is? If its not too
CPU hungry I can rewrite it in Visual Basic - otherwise C++ (yuk!) might be
called for. Is full baffling  for a long f-ratio Cassegrain difficult to
make or not possible to make? If its not possible - would the resultant
leakage degrade the image much for planetary/lunar  observing?

The person at University Optics I spoke to stated that their current
Foucault tester (which I ordered) is a new model with a micrometer knob. I
noticed that Takahashi makes DK Cassegrains for which they claim 1/20 wave
accuracy. Is this an achievable goal for my home brewed primary (9" F5)
using the Foucault tester?

        Thanks again for any advise provided - Tom