We present UBVI CCD photometry of two open clusters NGC 1798 and NGC 2192 which were little studied before .
Color-magnitude diagrams of these clusters show several features typical for old open clusters : a well-defined main-sequence , a red giant clump , and a small number of red giants .
The main sequence of NGC 1798 shows a distinct gap at V \approx 16.2 mag .
From the surface number density distribution we have measured the size of the clusters , obtaining 8 ^ { \prime } .3 ( = 10.2 pc ) for NGC 1798 and 7 ^ { \prime } .3 ( = 7.5 pc ) for NGC 2192 .
Then we have determined the reddening , metallicity , and distance of these clusters using the color-color diagrams and color-magnitude diagrams : E ( B - V ) = 0.51 \pm 0.04 , [ Fe/H ] = -0.47 \pm 0.15 dex and ( m - M ) _ { 0 } = 13.1 \pm 0.2 ( d = 4.2 \pm 0.3 kpc ) for NGC 1798 , and E ( B - V ) = 0.20 \pm 0.03 , [ Fe/H ] = -0.31 \pm 0.15 dex and ( m - M ) _ { 0 } = 12.7 \pm 0.2 ( d = 3.5 \pm 0.3 kpc ) for NGC 2192 .
The ages of these clusters have been estimated using the morphological age indicators and the isochrone fitting with the Padova isochrones : 1.4 \pm 0.2 Gyrs for NGC 1798 and 1.1 \pm 0.1 Gyrs for NGC 2192 .
The luminosity functions of the main sequence stars in these clusters are found to be similar to other old open clusters .
The metallicity and distance of these clusters are consistent with the relation between the metallicity and galactocentric distance of other old open clusters .