SYNTHETIC DDO COLORS

Calibrated synthetic DDO colours computed from Kurucz (1993) atmospher e models and fluxes are presented. The transformation equations to mak e synthetic colours consistent with the observational system are deriv ed by using a set of calibration stars for which atmosphere parameters are known from high resolution spectroscopy. The synthetic C(45-48) v ersus C(42-45) diagram is compared with observational sequences of Pop ulation I giants and dwarfs and a good agree ment is obtained. The met allicity effect in the synthetic diagram is discussed. The obtained re sults lead to the conclusion that synthetic calibrated DDO colours are valuable tools for analysing Population I and II late-type stars and for computing integrated colours of globular clusters and galaxies.