Hi Michel, here's my sketch. I found it a difficult observation with the SN so close to the core of NGC 3941. I needed a magnification of x343 to seperate them (and only at moments of good seeing). Because there is no chart from AAVSO (for the moment?) I didn't make an estimation. But he was weaker than the bright star (+/- mag 12) and a lot brighter than the two small stars (+/- mag 14, I needed averted vision for them).
Well done Jef.
The day before I was not really able to separate the two component, just a elongation was clearly visible at 172x with a Barlow 2X that was more easy to see that the magnitude of the two components was similar. Anyway I saw on internet somewere a picture made the 14th too, the image of the SN was as brillant as the core. And someone says somewere else that this SN must (in relation to the distance) reach +/- magn 11 ?.
So I'm not sure about my estimation but maybe with yours that means that this star is already fading, this is not impossible.