For historical reasons, the VRI photometry has produced several systems
which have quite similar, but the V-R and R-I indices are not exactly
in the same standard system. Therefore a datatype has been attributed to
each realisation of the VRI filter combination.
The datatype vik refers to the VI photoelectric photometry in the
system of Kron. In some observation sets, only the V and I colours
have been observed.
|V-I||:||V-I colour index|
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Last Update: 17 February 1998