1.91
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The observed phenomena do not originate from diffraction spikes. During the focus adjustment, I discovered that all stars exhibited elongated horizontal or vertical shapes (when out of focus). However, only when the lens was fully focused did the star manifest a cross-shaped pattern. The lens in question is a Tokina SZ 500mm F8 Reflex MF for Canon EF. The image below is the stacked image. I would appreciate any suggestions for further DIY improvements.  |
8.11
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A single sub of an out of focus bright star image would tell me more but from your example it looks like the lens is grossly out of collimation. You also mentioned a reversing spike pattern inside and outside of focus. That could indicate a severe amount of astigmatism. A good star test will tell all.
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B9 Dim Light Chaser: Compared to my vintage mirror lens, this is a fantastic result |
7.29
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As mentioned before, this looks like astigmatisms. Found a nice article on aberrations https://www.lonelyspeck.com/a-practical-guide-to-lens-aberrations-and-the-lonely-speck-aberration-test/ |
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Astigmatic coma, most likely as a result of poor flattener lens set-up/collimation. If you want something better than that you got to get a russian mak (MTO and siblings).
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