2005MNRAS.359..966D

We present deep CCD BVI photometry of the distant, old open cluster Berkeley 22, covering from the red giant branch (RGB) to about six magnitudes below the main-sequence (MS) turn-off. Using the synthetic colour-magnitude diagram method with three different types of stellar evolutionary tracks, we estimate values and theoretical uncertainties of the distance modulus (m-M)₀, reddening E(B-V), age τ and approximate metallicity. The best fit to the data is obtained for 13.8 ≤ (m-M)₀≤ 14.1, 0.64 ≤E(B-V) ≤ 0.65, 2.0 ≤τ≤ 2.5 Gyr (depending on the amount of overshooting from convective regions adopted in the stellar models) and solar metallicity.