An intermediate-band photometric system developed at the Geneva Observatory, Switzerland. It uses seven glass filters centred on the following wavelengths: U, 344 nm; B1, 402 nm; B, 425 nm; B2, 448 nm; V1, 541 nm; V, 551 nm; and G, 581 nm. The colours can be used to measure interstellar absorption, stellar temperature, gravity, and chemical abundance. See also vilgen photometry.
Subjects: Astronomy and Astrophysics.