  In this paper we analyse the evolutionary status of three open clusters: NGC
1817, NGC 2141, and Berkeley 81. They are all of intermediate age, two are
located in the Galactic anti-centre direction while the third one is located in
the Galactic centre direction. All of them were observed with LBC@LBT using the
Bessel B, V, and I filters. The cluster parameters have been obtained using the
synthetic colour-magnitude diagram (CMD) method, i.e. the direct comparison of
the observational CMDs with a library of synthetic CMDs generated with
different evolutionary sets (Padova, FRANEC, and FST). This analysis shows that
NGC 1817 has subsolar metallicity, age between 0.8 and 1.2 Gyr, reddening
E(B-V) in the range 0.21 and 0.34, and distance modulus (m-M)_0 of about 10.9;
NGC 2141 is older, with age in the range 1.25 and 1.9 Gyr, E(B-V) between 0.36
and 0.45, (m-M)_0 between 11.95 and 12.21, and subsolar metallicity;
Berkeley~81 has metallicity about solar, with age between 0.75 and 1.0 Gyr, has
reddening E(B-V)~0.90 and distance modulus (m-M)_0~12.4. Exploiting the large
field of view of the instrument we derive the structure parameters for NGC 2141
and Be 81 by fitting a King profile to the estimated density profile. Combining
this information with the synthetic CMD technique we estimate a lower limit for
the cluster total mass for these two systems.
