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2. Observations and reductions

The observations were carried out at the 1.5 m telescope at the San Pedro Martir Observatory during an observing season between 11 and 18 of March, 1994. In particular the observations of the stars in NGC 2422 were carried out on the night of 16/17 March. The telescope was fitted with a spectrophotometer which allows simultaneous obtention of data in the uvby filters and, almost simultaneously, in the narrow (N) and wide (W) filters which define Htex2html_wrap_inline1025.

The reported values for each star are the mean of three ten-  second integrations followed by one ten-second integration of the sky. A set of 31 of the brightest stars in the direction of NGC 2422 was measured. To be sure that the brightest stars were observed, concentric circles were drawn from the center of the cluster on the ID chart of Hoag et al. (1961) and all the stars in the inner circles were observed outwards. During the entire season, and in particular on this night, several standard stars were observed with the same telescope-photometer system in order to transform the instrumental magnitudes of the stars in the direction of NGC 2422 into the standard system. The photometric values for the standard stars were taken from the American Ephemeris and Nautical Almanac, 1994. The reduction was carried out following a previously described standard procedure (see for example Peña & Peniche 1994) which utilizes the Nabaphot package of Arellano Ferro & Parrao (1989) and Damadap of Parrao et al. (1996). The final results are presented in Table 1 (click here). The accuracy of each reported data point can be determined through the following considerations: the dispersion of the standard stars which gives the repeatability of the season and whose uncertainties are listed in Table 2 (click here) and the statistics for the fluxes measured for each star as a function of magnitude which are presented in Table 3 (click here).

Table 1: tex2html_wrap_inline1027 photometry of NGC 2422

Table 2: Accuracy of season from the dispersion of the standard stars

Table 3: Uncertainties versus magnitude for the observed stars

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