Star testing

I have two questions on star testing for the group:
My own experience with star testing is that I can recognize a near perfect test, as well as a the common defects that manifiest in a less than excellent mirror. However, I do not have a "feel" for how such defects translate into wavefront error or Strehl.
I recently tested a mirror (12.5" F6) at ~40X/inch. Seeing was 7/10. The mirror was touted as having a 0.94 Strehl ratio. By my test, however,the mirror yielded sharp,even, outside of focus concentric rings with washed out nearly undescernible inside focus rings - possibly suggesting some combination of spherical aberation and a turned edge. Some tube currents were visible as fell, but these in no way obscured the outside focus pattern. Nor did the effects of seeing. My first question then is this:
Is the star so very sensitive that a >0.94 Strehl mirror could yield such a test.
Second, due tube currents effect the inside focus image more than the outside focus image?
Joe

How about the in-focuse star images?

Dmitri

Several thoughts come to mind. First, Strehl numbers are tested and calculated prior to a coating being applied. Diaganol also important.

Also mounting and support can be very important as is cooling.

What does the in focus star look like at very high power on a nite when you actually can see steady diffraction rings? With a turned down edge, your in focus stars will have "flairs" on them which looks like my astigmatism does but if your not astigmatic, you might not know what I mean. But numerous mini diffraction spikes emminating from the center of main diffraction spikes on a bright star.

I also think it's possible that tube currents and most definately upper atmosphere can affect star test iside focus. As when i swing away from test star and put that same focus on a planet, I can actually see the outer portions of the jet stream passing by, even if the seeing looks pretty steady.

Kevin