We present multichromatic isochrone fits to the colour magnitude data of the globular cluster NGC 6366 , based on HST ACS/WFC and SOAR photometric data .
We corrected the photometric data for differential reddening and calculated the mean ridge line of the colour magnitude diagrams .
We compared the isochrones of Dartmouth Stellar Evolution Database and PAdova and TRieste Stellar Evolution Code both with microscopic diffusion starting on the main sequence .
Bracketing all previous determinations of this cluster we tested metallicities from [ Fe/H ] =–1.00 to [ Fe/H ] =–0.50 , and ages from 9 to 13 Gyrs .
After determining the total to selective extinction ratio only from stars belonging to this cluster , R _ { V } = 3.06 \pm 0.14 , we found the parameters for this cluster to be E ( B - V ) = 0.69 \pm 0.02 ( int ) \pm 0.04 ( ext ) , ( m - M ) _ { V } = 15.02 \pm 0.07 ( int ) \pm 0.13 ( ext ) , Age = 11 \pm 1.15 Gyr .
Evolutionary models fail to reproduce the low–T _ { \mathrm { eff } } sequence in multi–band colour magnitude diagrams , indicating that they still have an incomplete physics .
We found that the Dartmouth Stellar Evolution Database isochrones fit better the sub giant branch and low main sequence than the PAdova and TRieste Stellar Evolution Code .