Fundamental properties of the open cluster NGC 2355

NGC 2355 is an old open cluster in the outer part of the galactic disk (l = 203 degrees.4, b = +11 degrees.8) which has been little studied until now. This paper presents the first astrometric and spectroscopic investigation of this cluster We have measured precise absolute proper motions from old C arte du Ciel plates, POSS-I plates and recent CCD observations obtained wit h the Bordeaux meridian circle. The proper motion data reveal 38 highly pro bable cluster members down to B-lim = 15 mag within 7' of the cluster cente r. We have also obtained ELODIE high resolution spectra for 24 stars. Seven teen of them are confirmed to be members of the cluster on the basis of rad ial velocity. Eight of them are fast rotating turnoff stars for which the p rojected rotational velocity has been determined. The spectroscopic observa tions have also provided estimates of the physical parameters T-eff, log g, [Fe/H], M-V of the 24 target stars. Two stragglers have been identified in the cluster. Combining our astrometric and spectroscopic results with prev ious UBV photometry and recent JHK(s) photometry from the 2MASS survey we h ave derived the fundamental properties of the cluster: metallicity, age, di stance, size, spatial velocity and orbit.