[vsnet-chat 696] Comparison sequences

[bas@lowell.Lowell.Edu (Brian Skiff)]

     I spoke with Janet Mattei at the American Astronomical Society
meeting a few weeks ago.  She told me that they (AAVSO) were planning
a program to produce new charts for all their program variables that
included both "visual" and standard V magnitudes (plus some color, such
as V-R) so that both visual and CCD observers data could be standardized.
Apparnetly, Richard Stanton is re-examining the color term between "visual"
and V as part of this effort.  For the moment, a rough transformation
is:  mv = V + 0.2(B-V) for the dark-adapted visual response.
     My feeling is that sequences should be set up with CCD observers
in mind, and include V and a color such as V-R or V-I and perhaps B-V.
The visual sequences, which need not be so precise, can be derived from
this more accurate data in a consistent way.
     I a few years time the big digital surveys (GSC version 2, USNO, etc.)
should have enough calibration data available to put their data on the
standard systems, although the results on a per-star basis may still be
somewhat noisy (+/- 0.2-0.4 mag.).
     There is a lot of work to be done.  Much of the problem could be
solved by even a few amateurs willing to do "all-sky" photometry, but it
seems the number able/willing to do this is inexplicably close to zero.

\Brian

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