1 Introduction

Our actual knowledge of the red giant phase in the evolutionary history of the stars is still rather uncertain and incomplete. This is mainly due to the lack of numerous and sufficiently accurate observational data of red giants in open clusters to be compared with the theoretical predictions. In particular, intermediate-age open clusters are in an evolutive stage which is well suited to study the morphology of the red giant branch as well as to check the issue of convective overshooting (see, e.g. Bertelli et al. 1985).

NGC2354 (C0712-256; Trumpler class III-2m) is an intermediate-age open cluster located in Canis Major at (B1950) $\alpha$ = $7^{\rm h}$ 12$\hbox{$.\!\!^{\rm m}$}$2, $\delta$ = -25$\hbox{$^\circ$}$ 39$^\prime$; l= 238$\hbox{$.\!\!^\circ$}$42, $b = -6\hbox{$.\!\!^\circ$}$80. Although it is interesting for the number of red giant candidates it contains, this cluster has so far received little attention. The only photometric study was published by Dürbeck (1960) who derived a reddening E(B-V) = 0.14, a distance of 1850 pc and an age of 7.0 10⁸ years. These values, however, are rather uncertain as they have been determined from UBV photographic data. More recently, Ahumada & Lapasset (1996) reported preliminary results of a CCD UBVR photometric study in an area of about 10$^\prime$ centered on NGC2354. They obtained a mean reddening E(B-V) = 0.15, a distance of 1445 pc, and a somewhat larger age of about 1 Gyr. A photometric search for variable stars among the blue stragglers (BS) in this cluster led them to the discovery of one eclipsing binary BS (Lapasset & Ahumada 1996).

As part of a long-term project to determine abundances and astrophysical properties of red evolved stars in southern open clusters, we present here Coravel radial-velocity observations and accurate UBV, DDO and Washington photometry of red giant candidates in the field of NGC2354. The present data are used to discuss cluster membership, to detect spectroscopic binaries among the red giants, to determine individual E(B-V) colour excesses as well as to derive the cluster metal content. Preliminary results on the NGC2354 red giants were published by Clariá & Piatti (1994).