I ran out of comp stars (since solved that particular issue) due to the faintness of the star last night. I made it 16.1 against comp 150, and thereby hangs a tale...
To solve the issue above I looked at a (g) scale chart which bore a note to the effect that V730 has a 16.3 companion 1" of arc away, so - was I estimating the combined magnitude of the variable and this companion? Looking at the above estimate (which was 150-11) some might be thinking a step estimate of 1.1 whole mags might be pushing things? However for several years, pre-charting group, I have been doing just this in order to create visual sequences, and these on recent checking have proved really quite accurate, so I am reasonably (no more than that) confident that the above is OK.
With reference to the companion, and possible combined estimate, the calculation
mTOT = −2.5 log10 (10−0.4m1 + 10−0.4m2) isn't too practical here because - by definition - one of those stars is variable, and because mTOT itself is an estimate!
I'm measuring 15.6 mag in V. Closeup review of my image shows no obvious hint of the companion, so it must be integrated into the measurement.