Quote:
Originally Posted by Andrew Pearce
As with most things, it's not straightforward! The relationship between the vis. magnitude a visual observer sees & Johnson V mag does depend on the individual observer!(.....)
(......)An excellent paper was written by R.H Stanton entitled "Visual Magnitudes and the 'Average Observer':The SS Cygni Field Experiment"
in the Journal of the AAVSO back in 1999.
(.....)The average correction between visual and V magnitudes was found to be:
visual mag = V + 0.210 x (B-V)
(.......) "random errors on the order of 0.2 magnitude can be expected when data from many observers are combined".
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Thanks for that, Andrew.
Your useful answer saves me a lot of time , as I am
fully occupied ("up to my neck") in large quantities of data about NGC 5643!
The combined error of 0.2 sounds about right for the AAVSO observers' visual data about the apparent magn. of 2013aa, as long as one ignores statistical outliers among the scatter of data points...... for instance. there is a cluster of visual observations near 11.1 to 11.2 visual magn. which
I think should be ignored in calculating a mean magnitude of the SN. Perhaps these observations are the result of the sort of "wishful thinking" and "cognitive-perceptual bias" that I mentioned; these observers perhaps
wanted the SN to be closer to magn. 11
While I am not particularly statistically savvy, I do look at a lot of numerical galaxy data, both the good and the bad and the ugly, so I have a good feel for the sort of bad data points that should be rejected in an analysis.
Perhaps AAVSO should be less "democratic" and only accept estimates from the most accurate visual observers!! It is, after all, possible to
measure the average error of a specific observer.
cheers, Robert
"Science is not about democracy, or about sympathy for the underdog or for the weaker workers. It is about getting the best and most hard-working people to throw 'everything they've got' at a difficult problem"
- madbadgalaxyman