name a scope that meets the 1.2 criteria posted by Roland
I think there is only a very weak connection between the
FWHM on images and optical quality. Some criteria like
1.2" makes almost no sense. The FWHM will mostly depend on
seeing conditions high in the atmosphere, mount tracking
accuracy, mount vibration, pixel size, tube currents,
and probably lastly optical quality. Provided the optics
are diffraction limited (Strehl ~80%) the image FWHM is
going to be determined by something else.
The best "image quality" usually results from setting the
pixel size to roughly the seeing FWHM (i.e. minimizing the
CCD read noise per resolution element). Hence, as a matter
of observer practice, you are not going to see many FWHM much
smaller than 1". Reasonable observer choices are going to set
the FWHM, not the optical quality.
Is there a correlation between use of high end equipment and
resulting small FWHM? Perhaps. But it is probably related
to an overall effort to push the image quality (best
locations, waiting for good seeing, solid high $ mounts, large
format CCDs, etc.). The $ spent on the OTA is probably
the smallest contributing factor.
Anyway, theres my personal (and professional) take on this.