A system of photoelectric photometry that uses six filters with the following central wavelengths and bandwidths: U, 352 and 44 nm; V, 422 and 74 nm; B, 490 and 109 nm; G, 570 and 108 nm; R, 714 and 165 nm; and I, 1027 and 192 nm. The system was introduced primarily for the study of interstellar absorption, but is now obsolete.