I used Mu Pic (HD46860) which is a B9Ve star about 1 1/2 deg away from the SN. I just take 30 sec exposures x 5 of the calibration star and then divide it by appropriate Pickles spectra. This then gets smoothed and becomes the response curve. It is pretty constant from night to night but is affected by the altitude of the star affecting the blue end of the spectra.
I only have 2 nights of photometry from 29th and 30th.
There was only a 0.01 change in V mag over the 2 nights so this is inconclusive. The AAVSO data isnt conclusive either as there is quite a bit of variation betrwwn observers.
see the
graph
It's cloudy tonight so nothing from tonight.
Terry