Photographic photometry with filters of the following wavelengths and bandwidths: U, 359 and 49 nm; G, 466 and 52 nm; and R, 641 and 40 nm. The filters and photographic emulsions were selected so that the colour excesses E(U − G) and E(G − R) were approximately equal. There are no standard stars for RGU photometry; instead, UBV standards are converted into U, G, and R respectively. The system has been used extensively to deduce the structure of the Galaxy from star counts.
Subjects: Astronomy and Astrophysics.