I have used the AC Ronchi test for testing a few refractors lately. I am using a home built on-axis version of the tester with beam-splitter to avoid vignetting.
A 50mm F10 FH (my first scope). The tiny 50mm is of course no contender here.
80mm ED F8 by 'Kenko'. The 80mm ED has an outer zone and massive color.
Here is a Tak FS102. I am surprised about the bending of the lines. I think the 80mm ED is an interesting comparison with the Tak where both don't have straight lines indicating S.A. But the Tak has the upper hand as the Fluorite material (allegedly used in the lens) deals better with color.
Here an AP130. Notice the ring-zone polishing artifacts! Could this be from aspherizing?
I have an older analysis of the AP130 as shown below in comparison with the AC Ronchi photos.It is noteworthy that the wobbly surface comes to 0.98 Strehl and the rings are approximately matched between Ronchi and IM test.
160mm F6.6 CFF. The 160mm is similar to the AP130 in the straightness of the Ronchi bands but with more 'ripple' due to aspherization. It would be interesting to know the magnitude of the 'ripple'.
Copyright images Gert Gottschalk.
Copyright Bilder Gert Gottschalk
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