VizieR caltalogue

[angelof]

Greetings all
I am using VizieR to obtain info about certain stars.

http://vizier.u-strasbg.fr/

Is anyone familiar with it?
If so, what is the difference between B-V colour index and V-I colour index

Thanks

[Merlin66]

Wecome to IIS!!
The B-V index is a measure of the redness of the star (Blue-Visual)
The V-I gives the IR index, useful for cooler stars which radiate more in the red and IR
(See "Introduction to Astronomical Photometry" by Budding & Demicran, p64 for further detail - they start with the V-R index....)

[angelof]

Thanks a lot. I understand now.