[vsnet-chat 2512] Re: [AAVSO-DIS] B-V to V-R

[Brian Skiff <bas@lowell.edu>]

     Lew Cook provided some explanation of the relationship between the 
photometric V-R color and the B-V color for stars of ordinary color.  Such
a relationship can be used, for instance, to determine a fairly accurate
R magnitude for a star if the only data you have is the V magnitude and the
B-V color.  In the range 0.3 < B-V < 0.9 the relationship is about as good
as you can actually measure either B-V or V-R---if you think you have B-V
reliably, then you hardly have to observe V-R itself, but can get it quite
well enough from the formula.  For red stars the relationship veers away
from a simple linear one, and the properties of red stars are such that
a certain B-V color doesn't always have a single corresponding V-R color.
     The reason for using Landolt stars to determine the relationship was,
as Lew mentions, simply because those well observed by Landolt are considered
system-defining standard stars whose brightness and colors are accurately
known.

\Brian

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp