Mike, your Capella images look pretty darn good, and they appear to be close enough to the same defocus either side. Close enough to be telling. I cannot work with the blue Alph images. Outside appears too much further from focus than inside for my liking.
However, your defocused Capella images and the shadows are close to the same diameter (upon visual inspection), with a very slight amount of over correction as evidenced by some alternating slight variation in the inner and outer ring brightness on both sides of focus. Inside, the inner ring is a tad brighter indicating the center is focusing short, outside the outer ring is a tad brighter indicating the edge is focusing a bit long. The shadow is a tad larger inside focus which is normally associated with under correction, so not sure what to make of that other than it does not appear significant in any case. (Possibly the affect of a slight zone near the center, sometimes associated with a bright inner ring and large shadow, or the size of the obstruction).
I'd argue for a correction significantly and assuredly better than 1/4th and likely even better than 1/6th PV of primary spherical. How much better than that is anyone's guess, I am just sure it's not 1/4 waves PV LSA and appears to be better than 1/6 waves PV LSA. Based on those images, inside and outside are closely similar and /could/ be as good as 1/8 waves PV LSA. I don't normally go out on a limb like this, however your Capella images look very good in terms of correction. Saying that is not evidence of the actual PV of combined aberrations, as astigmatism may have a larger value, rather just an approximate read on spherical correction. Generally and very slightly over corrected with some minor deviations from a smooth over correction across the surface. Totally normal. No optic is perfect.
There appears to be a shallow over corrected zone as evidenced by the darker ring(s) inside focus between the bright inner and outer rings, and a little brighter ring(s) between both bright diffraction rings outside focus. Not enough to worry about, certainly. Astigmatism still evident, though, but no significant and noticeable coma to my eye. At least not to the level of pretty good collimation you seem to have attained. (Interestingly, astigmatism appears closely oriented with your spider vanes...hmmm).
That's my read on it, others may differ...but I'd suppose, astigmatism aside for the time being as it may be fixable, we'd agree your Capella images indicate a very good optic. Enough to say you should be very happy with the images, especially if the source of astigmatism can be isolated and corrected.
Edited by Asbytec, 12 December 2019 - 11:53 PM.