My Wife Can Stop Insulting Big Bertha

With the adjustments mentioned here, the old girl shows more detail on Jupiter at 222x than I can draw--gobs and gobs of belts, festoons, and detail just below the edge of what I can describe. However: the collimation doesn't stay for long. I think the mirror supports need to be a bit tighter against the mirror, and the diagonal holder needs to be a bit more tightly screwed into the spider.

For its inches of aperture, I would agree that the image quality degrades faster than I would expect. But at the same magnification, it shows more detail than smaller scopes. This is expected, since resolution increases linearly with the diameter of the objective. Even a so-so 17.5" mirror should handily outperform even a very good 5" refractor under stable skies (which I have).