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Old 28-02-2013, 04:05 PM
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Merlin66 (Ken)
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Join Date: Oct 2005
Location: Junortoun Vic
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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....)
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