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In article <1142650864.146480.44650@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Yegor <yegorplam@xxxxxxxxxxxxx> wrote:
> We are interested in star I magnitudes. Hipparcus catalog has
> V-magnitudes. Is it possible to compute I-magnitudes from
> V-magnitudes?
No, you need to know more than just the V magnitude. Different
stars with the same V magnitude can have quite different I
magnitudes.
> Is that what the V-I mag field is for?
Yep -- that's the extra information you need!
> If so, how to use it?
Remember your high-school algebra? Let's mess a little with that
to find out the answer to your question:
V - I = (V-I)
I - V = -(V-I)
I = V - (V-I)
Got it?
> Also, what is the ratio of red stars to blue stars (or a good web
> resources to find out)?
There are many kinds of rations - what kind of ratio are you
interested in?
--
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Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
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