Intrinsic colour calibration for F, G, K stars

We derive an intrinsic colour calibration for F–K stars using broad band Johnson colours and line indices KP and $HP2$. Through this calibration we can determine $E(B-V)$ of an individual star within 0.03 mag. The $E(B-V)$ values thus derived are in excellent agreement with those derived from Strömgren photometry through the Schuster & Nissen (1989) calibration. The agreement is also good with the reddening maps of Burstein & Heiles (1982) and Schlegel et al. (1998), although in this case there exists a small offset of about 0.01 mag. This calibration may be applied to the large body of data of the HK survey extension which will be published in the near future