UBV system

UBV system

[¦yü‚bē¦vē ‚sis·təm]
(astronomy)
A system of stellar magnitudes in which an object's apparent magnitude is measured at three wavelengths, labeled U, at 360 nanometers; B, at 420 nanometers; and V, at 540 nanometers; and is characterized by the color indices B-V and U-B, which are both defined to be 0 for a star of spectral type A0. Also known as Johnson-Morgan system.
References in periodicals archive ?
(7.) Mermilliod JC: Photoelectric Photometric Catalogue of Homogenous Measurements in the UBV system. NASA, Astronomical Data Center, Selected Astronomical Catalogues.
Photometry measured on the Johnson UBV system on the nights of 12, 25 and 26 July 1978 with the 0.5 and 1.0-m reflectors at Sutherland has yielded V= 12.68, B-V= +1.31, U-B= + 1.00.
So successful was the UBV system that it was extended redward with R and I filters to define standard red and near-infrared magnitudes.