Abstract
From photoelectric uvby-beta data and recent accurate synthetic and spectroscopic values of T_eff and log g for 50 F-G supergiants, we have calculated functional relationships that lead to initial estimates of effective temperature and gravities for these types of stars. It is shown that while the T_eff relationships are calculated using the data on young massive supergiants, they are also valid for evolved stars of similar temperatures like post-AGB and RV Tau stars. The gravity can also be predicted from the Delta [c_1] index with an uncertainty of about 0.26 dex. Although a clear and significant trend between M_V and Delta [c_1] is seen, no calibration is found that predicts accurate values of M_V.
