2008BaltA..17...67P

We present CCD observations in the Washington system C and T₁ passbands down to T₁∼18.5 in the field of Ruprecht1, a poorly studied open cluster located in the third Galactic quadrant. We measured T₁ magnitudes and C-T₁ colors for a total of 862 stars distributed throughout an area of 13.6x13.6 arcmin. The cluster turned out to be very small; its linear radius being 2.6±0.2 pc, as estimated from star counts in appropriate-sized boxes distributed throughout the entire field observed. By fitting the zero-age main sequence to the T₁ vs. C-T₁ color-magnitude diagram, we derive E_B–V = 0.25±0.05, independently from the cluster's metallicity. Our analysis suggests that Ruprecht1 is moderately young. In fact, adopting the theoretical metal contents Z = 0.02 and 0.008, which provide the best global fits, we derive heliocentric distances of d = 1.9±0.4 kpc and 1.5±0.3 kpc and ages of 200±47 Myr and 251±58 Myr in each case.