I see what you're saying more clearly here. Enough power that stars of the same magnitude (zeta bootes with 417x magnification) would reveal an airy disk.
In other words, their IS an airy disk when it is in focus. I don't understand what you mean you saw the "elongated shape" (is zeta bootes an asteroid??).
The gest of this is that i should be seeing a star with similar magnitude at magnification when it begins to show an airy disk. THAT, is the magnification threshold to use?
Just seems it would be alot easier and faster to use various eye pieces until i do........see a disk with Jupiter's moons. It's the same thing, i'd think.
If i get a chance i'll crank up the magnification alot more to see what i get with the larger moons, if possible.
If i get an airy disk with a star, how do I know if that's all I'm getting when i view one of Jupiter's moon also? (rather than an "actual" disk of the moon).
Zeta Bootes is a close binary star that is nearing its closest approach (when it won't be resolvable visually). What I described was the appearance of the two overlapping airy disks. They overlapped because they were closer than the resolution limit of the aperture. In my 20" I could still resolve them individually with a gap between, but only when the seeing was good enough to see the spurious disks.
As to how you know a diffraction pattern from a tiny disk: experience. I have explained some of the ways I can tell at the threshold and even beyond. The lack of a first diffraction ring, instead seeing a somewhat blurred disk is a giveaway. The same applies to double stars where one can interpret disturbances in diffraction patterns even when the seeing is not sufficient for resolution...how...by comparing to similar magnitude stars and recognizing odd interference patterns or irregularities.
The problem you have had is that it doesn't sound as though you have used enough magnification to notice there was an airy disk pattern on bright stars. The eye needs some scale, typically 120 arc seconds of apparent size as a minimum, if not 180 arc seconds to better see something vs. detection only as a point. Last night I did some backyard observation of Neptune and Triton to remind myself of the appearance in smaller apertures:
I took another look tonight with the 80ED and then the 10" Dob in town to remind myself how Neptune's disk appears in smaller apertures. Skies were about 18.9 MPSAS (red/orange transition) and about 4/10 Pickering in the 10".
The strong color contrast was even noticeable in the 80, although there Neptune was more of a slate gray at 150x rather than a more obvious blue. Even at 100x I could tell that Neptune was a tiny, barely resolved, soft disk. At 150x and 200x there was some interesting comparison with the ~9 mag star to the south. While Neptune's disk scaled larger in size, the comparison star had a noticeably smaller, more intense (but overall less bright) spurious disk. Neptune was also more steadily seen compared to the fluctuations in brightness of the central spurious disk of the stars.
The 10" made Neptune brighter and easier to discern as a somewhat sharper disk at 208x, more so at 250 and 313x. The blue was more readily seen than in the small scope. Triton was visible with certainty after a bit of study at 250x. It was less readily seen at 208, equally well seen at 313x with greater separation, and more difficult at 417x due to seeing disruption impact on the faint moon.