[Aavso-photometry] B-V vs. V-I

[Wolfgang Renz]

Hi Tomas

> Take the Landolt catalog and plot B-V vs. V-I:
> http://astrosurf.com/~tlgomez/bv-vi.png
> For stars with B-V > 1.3, the plot splits into two
> branches. Why is this so?.

One branch is probably for the main sequence dwarfs and
one for the giants.

Without reddening due to interstellar extinction or with all
stars at the same interstellar extinction one can make a
rough luminosity classification this way.

Clear skies
 Wolfgang

-- 
Wolfgang Renz, Karlsruhe, Germany