SM, Chris,

Thank you for your help.

Chris, could you clarify a couple of points:
1) "Between the errors introduced by the required transforms, and the
quality of the data itself, I doubt you can expect better than a couple
tenths of a magnitude in I in most cases"

By "errors in transforms" do you mean that the formulas (similar to
what SM suggests above) are statistical curves which result in rough
approximations for any particular case?
By "couple of tenths" do you mean that the error I mag should have an
upper bound of 0.2? (Which is quite sufficient for my purposes, btw.)


I am a newbie when it comes to stellar stuff (magnitudes and color
temperature in particular), so it'll take me a bit to figure out
exactly what you meant by "BT,VT - Johnson, then use VI".

As far as "What data do you want to work with?"... I guess whatever's
in the Hipparcos catalog.

Thanks again.

-Yegor Plam