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 Stromgren 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.Comment: To be published in A&A