Quote:
Originally Posted by Satchmo
Peter, this kind of performance may be possible on a ray trace program but the reality of diffraction theory says its impossible. For a perfect F4 system of any design the diameter of the Airy disc to the first mimima of the airy pattern will be about 6 micron and then the 50% central obstruction will throw light into the first and second diffraction rings making them very bright , probably doubling the best blur spot diameter to twice that in the presence of seeing.
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Not really. Airy disk size and spot size are two different paramaters. I think you knew that
The physical size of the airy disk is purely a function of the F-ratio. 4.7 microns for a F3.8 system. With 305mm of aperture you'd be looking at 0.84 arc sec of sky.
That is not the same as the spot size.
Spot size (and shape) depends on all sorts of variables, but in a nutshell, mirror/lens quality & optical design.
You only need to look at the off axis "sea-gulls" delivered by most camera lenses to see what happens when a design is not corrected well.
The Honders design covers a 3 degree field with essentially perfect color correction from 400 to 1,000 nanometers (UV to IR). The telescope is fully corrected for spherical, coma, astigmatism, field curvature and distortion, longitudinal and lateral chromatic aberration.