Cepheus OB3: Search for Faint Members

uvby–H$_{\beta}$ CCD photometry of NGC 1817 and NGC 1807

“…IRAF 1 routines were used for the reduction process as described below. Dome flats were taken to check shutter effects on the images of the OAN and CAHA telescopes where significant effects were previously noted (Galadí-Enríquez et al 1994;Jordi et al 1995). In the current configuration of all the telescopes used this effect is negligible.…”

“…Those standard stars with residuals greater than 2σ were rejected. Following Jordi et al (1995), the reduction was performed for each night independently and in two steps.…”

“…The internal errors of the individual measurements were computed as described by Jordi et al (1995), taking into account the errors in the instrumental magnitudes on the one hand, and the errors in the transformation equations on the other hand. Final magnitudes, colours and errors were obtained by averaging the individual measurements of each star using the internal error for weighting (Galadí-Enríquez et al 1998;Rosselló et al 1985).…”

Secondary ${\boldmath UBVRI}$-CCD standard stars in the neighbourhood of Landolt standard stars

“…The data were acquired in the course of several campaigns devoted to obtain deep UBV RI Johnson-Cousins CCD photometry of open clusters and stellar associations (Cep OB3, IC 348, NGC 1750/NGC 1758; Jordi et al 1995;Trullols & Jordi 1997;Galadí-Enríquez et al 1998) in November 1991, October 1993, December 1993and December 1994 at the telescopes of Centro Astronómico Hispano-Alemán (CAHA) and Observatorio Astronómico Nacional (OAN), both in Calar Alto, Almería (Spain). In these observational runs, Landolt stars were used as reference for the transformation to the standard photometric system.…”

“…Table 2 gives the quantum efficiency of the detectors at the central wavelengths of the standard UBV RI filters. The reduction from raw images to standard photometry was performed following Jordi et al (1995), and we refer to them for a fully detailed description of the procedure. In the following paragraphs we summarize the main steps of this process.…”