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Hi Eric,
My images are unfiltered. I think that is why Colin uses the red survey images from the various DSS surveys so I think the red survey is a good match. V filters I think are usefeful for measuring the visual magnitude by evening out the differences in the various ccd chips available and the bulk of SN discoveries are very faint and not likely to be observed visually. I think the AAVSO charts are based on V mags. In fact many of the discovery CBETs I see by other amateurs are all unfiltered and use the red survey as their reference, so long as you specify to CBAT which survey is used as a reference image. Colin also checks the IR survey, as in Stuarts case his ST8 is more IR sensitive. This recently showed a faint suspect what turned out to be a variable M star that was in Stu's image, was in the IR survey but not on the red survey. Colin uses both the GCVS and AAVSO's online list of variable stars. Colin knows this stuff inside out so he can probably give you better information than I have. He will be at the meeting on Saturday night.
PeterM.
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