Classification of Population II Stars in the RGU System

The theoretical treatment of the blanketing effect and the first photometric results had shown that the separation of stars of different metal content should be better in the RGU system than in the UBV system. A three color photometry of the globular cluster M5 is undertaken to show the position of these stars in the RGU two-color diagram, to derive the conversion formulae between the two photometric systems for these stars and to use the results for the classification of population II field stars in statistical investigations of the galactic halo.