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: 4, b = +11: 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 Carte du Ciel plates, POSS-I plates and recent CCD observations obtained with the Bordeaux meridian circle. The proper motion data reveal 38 highly probable cluster members down toBlim =1 5mag within 7 0 of the cluster center. We have also obtained ELODIE high resolution spectra for 24 stars. Seventeen of them are confirmed to be members of the cluster on the basis of radial velocity. Eight of them are fast rotating turnoff stars for which the projected rotational velocity has been determined. The spectroscopic ob- servations have also provided estimates of the physical parame- ters Te;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 previous UBV photometry and recent JHKs photometry from the 2MASS survey we have de- rived the fundamental properties of the cluster: metallicity, age, distance, size, spatial velocity and orbit.