The study of open clusters located in the direction of stellar associations and/or extended gas regions is of great interest in different astrophysical aspects. By analysing clusters physically connected with them it is possible to investigate the internal and environmental conditions during the star formation processes (see, e.g., Caillault 1994; Shaoguang 1995; Henning et al. 1995). The information that could be obtained about the structure, spatial mass distribution, and initial luminosity function of these clusters, constitutes an important tool to the knowledge of what happened since their births until the present (Massey et al. 1995; Murray & Lin 1996). On the other hand, if the clusters are not connected with stellar associations - which are generally related to HII regions - one can argue about the uneffectiveness of the star formation in those zones of the galactic disk.
As part of a program dealing with the spatial distribution of O and B stars in Canis Major, Clariá (1972, 1973) studied photometrically two open clusters (NGC2335 and NGC2343) located in the direction of the CMaOB1 association. He suggested that both clusters most likely form a double system. Their estimated distances (1050 pc and 960 pc, respectively) and the one of 1150 pc derived by Clariá (1974b) for CMa OB1 suggest a possible physical relation between the clusters and CMa OB1. However, the ages derived for the clusters ( 100 Myr) make it highly improbable that these clusters and the association could have been originated from the same protostellar material.
NGC2323 (OCI-559, , ), located nearly at the edge of CMa OB1, could be another candidate belonging to the association. This cluster was studied by several authors using photographic photometry (see, e.g., Cuffey 1941; Hoag et al. 1961; Mostafa et al. 1983), who placed it between 520 pc (Rieke 1935) and 1170 pc (Hoag et al. 1961) from the sun. Although the age of NGC2323 was determined by Barbaro et al. (1969) and Mostafa et al. (1983), there is no agreement between both estimations. In fact, the former derived an age of ( 107 yr, whereas the latter obtained yr.
In order to perform a better determination of the cluster parameters as well as to clarify the probable connection of NGC2323 to CMaOB1, we have carried out UBV photoelectric photometry in the cluster field. Five probable red giants were also observed in the DDO system to evaluate cluster membership and to derive reddening and metal content. In Sect. 2 we describe the observations and the data reduction. The analysis of the UBV and DDO photometric data is presented in Sects. 3 and 4. In Sects. 5 and 6 we derive age and discuss the cluster luminosity function. Finally, in Sect. 7 we analyze the possible connection of NGC2323 to CMaOB1. The principal results of the present study are summarized in Table 6.