SIMBAD references

Astrometry (positions and proper motions) and photographic BVR photometry were determined from a set of 29 photographic plates and CCD data in a region of 2.3x2.3° in the area of open clusters NGC 1750 and NGC 1758 in Taurus. The iterative central overlap algorithm was used for the proper motion calculations. Plate-to-plate transformations and astrometric magnitude effects are discussed in detail. CCD data interact with photographic material in three different ways: for the elimination of astrometric magnitude effects, for the photometric standard calibration of photographic plates and for building a CCD pseudo-plate used for astrometric purposes as any other photographic plate. A preliminary analysis of the resulting photometric and astrometric catalogue confirmed the reality of two different clusters in the zone (NGC 1750 and NGC 1758). There were no indications for the existence of NGC 1746.