UBVRI photometric standard stars around the celestial equator

It is pointed out that accurate, internally consistent, and readily accessible standard star photometric sequences are necessary for the calibration of the intensity and color data which astronomers obtain at the telescope. The photometric results provided in connection with the present study represent the first part of an effort which is concerned with the presentation of UBVRI photoelectric photometric standard stars in the magnitude range from 7 to 17 over as broad a range in color as possible. All of the photometric observations were made with a 31034 type photomultiplier used in a pulse counting mode. Some 15 to 25 standard stars chosen from Cousins' lists (1973, 1976) in the E-regions were observed with an 0.4-m telescope each night along with the program stars. UBVRI standard stars were observed periodically throughout the night. Observations with a 0.9-m telescope were also conducted. The UBVRI photoelectric observations take into account 223 stars.