[Aavso-photometry] Transformation equaions for only B, V and I filters.

[Lionel Catalan]

Transformation equations are usually written as 4 equations involving the
terms V, B-V, V-R, and R-I. Hence, they assume that one uses the set of
B,V,R, and I filters. However, when I use only 3 filters (B, V and I), it
would seem logical to use only 3 equations giving V, B-V and V-I to
calculate the transformation coefficients. Is this permissible? If so, is
there more uncertainty on the transformed I magnitudes than if the R filter
was also used? 
 
Lionel CTE