How to Figure Required Telescope Diameter?

AI Thread Summary
To determine the required telescope diameter for observing an object of a specific angular diameter, the discussion highlights the need to reverse the Dawes' limit formula. The original program incorrectly utilized the Nyquist-Shannon sampling theorem and photon wavelength, leading to inaccurate results. The focus is on using diffraction principles, particularly Airy discs, to calculate the necessary mirror size without sampling considerations. Understanding the differences between Dawes' limit and Rayleigh's criterion is essential for accurate calculations. Clarification on these concepts is sought to improve the program's accuracy in determining telescope specifications.
willgtl
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A awhile ago I wrote a program to calculate various things like maximum resolving power of a given telescope's primary mirror, angular diameter of an object of a given size from a given distance and mirror diameter required to see an object of a given angular diameter.

However, I seem to have completely failed on the last part. I just now looked back at that program and got results of tens of kilometers when I know my result should've been mere dozens of meters. Looking at the code, I appear to have involved the Nyquist-Shannon sampling theorem and photon wavelength, with no recollection as to why.

I have a feeling I'm completely off-base. Could someone enlighten me on how to essentially reverse the Dawes' limit formula, and find the mirror size required for a given angular diameter? Thanks!
 
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From wiki:

"A calculation using Airy discs as point spread function shows that at Dawes' limit there is a 5% dip between the two maxima, whereas at Rayleigh's criterion there is a 26.3% dip."

Does this help? No sampling required, but it is based on diffraction.
 

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