I have been working on the AL Carbon Star certificate and have had a bit of trouble determining magnitude with the red color shift. I generally try to look at an area equidisant to the target star and nearby stars to get an averted vision take on the whole group. I know averted vision adds brightness so this seemed logical (I hope, been observing for a few years but new to the variable scene).
This has yielded some pretty decent results when the stars were roughly the same color. However once you get into to 10+ region with some significant color the carbon star won't come into it's own until you stare directly at it for a couple seconds. The star will literally appear to brighten in the process. Try doing that to a standard white star and you get the exact oppisite effect.
A really good example of this from last night was V CRB. Direct vision put it in the 9.5 region (max) but averted suggested something more like 11.5 (min). I checked the light curve this afternoon and it showed roughly the same ambiguity.
I know our eyes take a bit for the red photons to process and stars themselves vary in peak spectra. Maybe the averted/direct technique could be a biological light filter? That would be kind of cool if the case!
Anyway, just curious how the more seasoned observers out there tackle the problem. Thanks in advanced!