How to detect over or under correction?

I have seen several posts by experienced observers noting their scopes showed a bit of over or under correction. Can one actually detect over or under correction without actually doing a star test or using ronchi screen?

Bill,

H.R. Suiter addresses this question in both chapter 1 and Appendix 'A' of his excellent book 'Star Testing Astronomical Telescopes.' Star testing is the most sensitive test an amateur has for measuring aberrations - and the most fun, because we are under the stars!

Clear and steady skies (for testing),
Milt

The reason I ask this is because it has been difficult for me to tell with any accuracy if the diffraction rings are progressively brighter toward the outside/inside. However my scope definitely produces more defined diffraction rings intra focal...would that be any sort of indicator? thank you, Bill