Interesting information... thanks for posting. I definitely see more coma than that with my Canon 24 f/1.4 II, but when I'm taking night shots I am typically using a higher ISO and a longer shutter speed so that will automatically make the coma a lot brighter by comparison. My most common setting for aurora photography is ISO 1600, 8 seconds at f/2.0. It would be interesting if you could try that with your lens (and also try 4 seconds at f/1.4).