Precise reddening and metallicity of NGC 6752 from FLAMES spectra

Accurate reddenings for Globular Clusters could be obtained by comparing the colour-temperature relation obtained using temperatures from a reddening-free indicator (Hα) with that given by standard colour-temperature calibrations. The main difficulty in such derivations is the large errors in temperatures for individual stars due to uncertainties on the removal of instrumental signature for each individual star. The large multiplexing opportunity offered by FLAMES at VLT2 allowed us to obtain spectra centred on Hα at a resolution of R = 6000 and 5