A REVISED EFFECTIVE-TEMPERATURE CALIBRATION FOR THE DDO PHOTOMETRIC SYSTEM

A revised effective-temperature calibration for the DDO photometric sy stem is presented. Recently published photometric and spectroscopic ob servations of field and open-cluster G and K stars allow a better defi nition of the solar-abundance fiducial relation in the DDO C0(45-48) v s. C0(42-45) diagram. The ability of the DDO system to predict MK spec tral types of G and K giants is demonstrated. The new DDO effective te mperature calibration reproduces satisfactorily the infrared temperatu re scale of Bell and Gustafsson (1989). It is shown that Osborn's (197 9) calibration underestimates the effective temperatures of K giants b y approximately 170 K and those of late-type dwarfs by approximately 1 50 K.