5 Summary

We present the result of a long-term observational programme of IR photometry for an extended sample of giant stars. The analysis of colour-colour diagrams shows that the target of selecting a sample which covers the metallicity range found in our Galaxy has been properly accomplished. The JHK photometry is accurate to 0.02 mag and the L' photometry to 0.03-0.04 mag. These levels of accuracy will allow the determination of effective temperatures for the sample stars within and error of 1.5% by applying the Infrared Flux Method.

As a complementary result the new IR photometry has allowed an extension and improvement in the characterization of the TCS photometric system.

Acknowledgements

Based on observations made with the Carlos Sánchez Telescope of the Observatorio del Teide (Tenerife), operated by the Instituto de Astrofisica de Canarias. We are grateful to Terry Mahoney for the careful reading of the manuscript.