We have obtained BVI CCD imaging of Berkeley 17 , an anticentre open cluster that competes with NGC 6791 as the oldest known open cluster .
Using the synthetic colour magnitude diagrams ( CMD ) technique with three sets of evolutionary tracks we have determined that its age is 8.5 - 9.0 Gyr , it distance modulus is ( m - M ) _ { 0 } = 12.2 , with a reddening of E ( B - V ) = 0.62 - 0.60 .
Differential reddening , if present , is at the 5 % level .
All these values have been obtained using models with metallicity about half of solar ( Z=0.008 or Z=0.01 depending on the stellar evolution tracks ) , which allows us to reproduce the features of the cluster CMD better than other metallicities .
Finally , from the analysis of a nearby comparison field we think to have intercepted a portion of the disrupting Canis Major dwarf galaxy .