I have read Suiter's book and use it for reference along with many sources online. In star testing my telescopes, I have been mostly looking at the outer ring inside and outside focus. I don't expect any scope to test perfectly but I am trying to figure out the amount of Spherical Aberration and comparing what I see in my star test to images in the Suiter book and online.
I can see some difference in the intensity of the outer ring inside and outside focus that is similar to the picture of 1/8 wave in the Suiter book. But the inner rings in the Suiter book are quite different. When the outer ring is bright the inner rings have less intensity and the area is dark. Yet I don't think my inner rings are quite as dark. Hard to tell but they don't look as dark as in the book. Perhaps there are other aberrations in the mix?
I realize the pictures in the Suiter aren't real star tests but just drawings. How accurate are they to a real star test? I wish there was a compilation of star test images with someone evaluating and comparing them. I haven't found anything like this, at least, not all in one place.
I have yet to make a 33% obstruction to test my scopes. Suiter recommends this. But even with the obstruction, it is going to be very subjective and I will have to guess if the results are 1/10 wave, 1/8 wave etc.
No one said it was easy and I am sure it take lots of experience but I want to learn .