Abstract
Atmospheric extinction data, color coefficients for the original and new filter sets, and transformation residuals are given and discussed for 98 nights of 1 photometry observed at the San Pedro Martir Observatory in Baja California. The transformation residuals of filter set No. 1 are analyzed in terms of the physical parameters of the steilar atmospheres such as effective temperature, surface gravity and chemical composition. B-type stars and F and stars are emphasized. A non-neutral change in the atmospheric extinction is shown for 1982, due to the volcanic eruption of El Chichon.
