At final I had a good stable night in order to evaluate more acurately this scope.
With 123, 205 264 308 and 450x, the collimation was retouched, just a little, lucky I was.
Seeing was quoted 7-8/10 at 20H20UT, 3 quaters hour after sunset on SAO100949 of m6,0, near arcturus.
The 1st diffraction ring was well centered equally all around and the airy disk well clear and circular.
Elevation was 39° above horizon.
I pointed on arcturus to see in and out focus donuts at 2-3 wavelenght .
Sketches are shown under.
Evaluations was conducted with reference to the De Suiter book "star testing astronomical telescopes":
-roughness of optics: external ring donuts, in-out showed a figure corresponding between 1/20-1/40th wavelength, rather close to 1/20th,
-astigmatism: not especially marked on that point, say standing at less 1/10th wavelength,
-spherical aberration: say standing at less 1/8th wavelength,
-optical acuracy: say standing between 1/4 and 1/8th wavelength, rather close to 1/4th probably 1/5-6.
The ronchi test which is more qualitative had confirmed the above assessments.
The easy tester (6lp/mm) showed on arcturus straight bars with no inflexion especially at the outer diameter of primary.
It seemed that 2 bars, still straight, exhibited some very slight angle, this involves some residual astigmatism (not actually shown with the star test).
The 10lp/mm ronchi eyepiece use didn't confirmed the previous evaluation, bars were straight and parallel. This confirmed narrowly the star test results.
With adding the fact in-out donuts were always circular at the 205-264x magnifications.
The test was conducted on a m6.0 star, a little too dim, and on arcturus of m0,0, too bright. This should be performed on a m2-3,0 star in order to observe more subtilities.
Anyway the tests involve a scope status being not a melon, not an excellent scope but say an average good to good scope, quoted at L/5 more or less, of no specific aberration raising at a significant distroying amount. The roughness on the optical surfaces is say normal, better than a simple diffraction limit optics of 1/14th wavelength theorical.
At final a good buy for the 400 invested, and roughly a good buy.
A roddier test would be also a good additionnal, if I have the courage for performing.
Also a knife edge placed at the focus plan would be an help.
There was no planet visible, no moon visible at the time so this could be also a confirmation when viewing.
L/5 if well actual would help for performing on the target expected, planets in deep blue color also in near uv.
Hope this helps gents for selection of such scope, a CC.