I've had pro level lenses that didn't show a hint of fringing under difficult situations (backlit subjects, thin branches in bright light) still get a bit of purple fringe when shooting astro. Solution’s pretty simple: just turn on the auto purple fringing removal. If that doesn’t get it all lower luminance and saturation a bit in purple (something that’s dead easy in DxO PhotoLab, not so much in Photoshop. Dunno about LR, never used it)

I find purple fringe interesting as, if you use a prism to break up sunlight, you get an array of color — which does not include purple. I’ve read that it’s an artifact in our visual systems— what we perceive if there’s absolutely no green.

Purple doesn’t show up in primary rainbows either — but it does show in secondary rainbows. Apparently those secondary rainbows come from interference patterns.

What has all that got to do with purple fringe showing up on good achromat lenses? Dunno. Just thought I’d share my puzzlement.