BV photometry

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Measurement of a star's brightness at blue and yellow-green (visual) wavelengths; a subset of Johnson photometry. UBV photometry is much more frequently used, but the U (ultraviolet) band is omitted in certain circumstances, for example for red stars where there is insufficient flux in U, for short-period variable stars to speed the observations, or when observing with a refractor, since an objective lens absorbs most of the U light. The B–V colour index is a good indication of the temperature of a star; in conjunction with the spectral type, it can be used to measure interstellar absorption.

Subjects: Astronomy and Astrophysics.

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