2001PASP..113..267S

This paper is partly a review of the history of the making of the Mount Wilson Catalogue of Photographic Magnitudes in Selected Areas 1-139 (hereafter the MWC), begun in 1909 and completed in 1930, and it is partly the presentation of new photometric results concerning it. Photoelectric photometry of 435 stars in the 11 Selected Areas of SA 28, 29, 45, 55, 57, 71, 82, 94, 106, 107, and 118 of the MWC is given. The data are used to derive magnitude corrections to the MWC for these areas. Ten of the areas are in the Galactic meridional plane (Galactic longitudes of 0° and 180°). These are the same areas used by Becker in his Basel program of star counts for the study of Galactic structure.

The first purpose of the paper is to extend the Basel star counts to fainter magnitudes. For this, 200 inch photographic plates were measured to the plate limits near B=22, calibrated with the photoelectric photometry listed here. A second purpose is to derive certain properties of the catalog. The interests are (1) to determine the internal (random) measuring errors of the MWC as a function of magnitude after correcting for the systematic scale error in each area, (2) to test for a color equation between the corrected m_pg(MWC) values and the B_pe system that must be present because of the difference in reflectivity between silvered and aluminized mirrors, and (3) to test for possible distance-to-center corrections of the scale-corrected MWC magnitudes.

Photographic photometry is used to complete the count surveys in each of the program areas to the limit of the 200 inch plates. Color-magnitude diagrams are shown for each area, generally complete to V=20, B-V=2.0. The work is preparatory to an analysis for Galactic structure when the larger database is available in a program by Majewski using Kitt Peak 4 m plates, epoch circa 1975, that will be to provide both a deeper count survey in B and V and proper motions for the larger sample.