SIMBAD references

A reddening scale for F-G supergiants and Cepheids is presented. Supergiants with low reddenings or in clusters form the basis of the calibration. In this sense, it is entirely empirical. The data have been obtained in the Geneva photometric system. Comparisons with other reddening scales show no disagreement. The only problem is with Fernie's scale for Cepheids (1990), where a systematic trend exists. Its origin is not clear. It is suggested to extend the number of supergiants with independently obtained colour excesses in order to test the existence of a possible luminosity dependence of the calibration. A period-colour relation for Cepheids is deduced, on the basis of the present reddening corrections. It gives strong support for V473 Lyr being a second overtone pulsator.