I obtained differential photometry of many magnetic Chemically Peculiar (CP) stars in the Strömgren uvby system during the first six years (Sept. 1990 - July 1996) (year 1 is Sept. 1990 - July 1991, year 2 is Sept. 1991-July 1992, etc.) of the 0.75-m Four College Automated Photoelectric Telescope (FCAPT) on Mt. Hopkins, AZ (e.g., Adelman & Boyce 1995) to better determine the periods and the shapes of the light curves so that observations of various types taken at different times can be correctly phased together. The telescope measured the dark count and then in each filter the sky-ch-c-v-c-v-c-v-c-ch-sky where sky is a reading of the sky, ch that of the check star, c that of the comparison star, and v that of the variable star. This paper presents results on the magnetic CP stars HD 32633, 25 Sex, HR 7224, and HD 200311. Table 1 (click here) gives important information on the variable, comparison, and check stars from Hoffleit (1982) and Hoffleit et al. (1983) supplemented by values from Deutschman et al. (1976) and Oja (1983).
Figure 1: Differential Strömgren uvby photometry of HD 32633
plotted with the ephemeris HJD (
. Rakosch's (1962) uv values transformed to the u scale
are plotted as solid diamonds with the FCAPT values indicated
by plus signs
Figure 2: Differential Strömgren uvby FCAPT photometry of 25 Sex
plotted with the ephemeris HJD(
Figure 3: Differential Strömgren uvby photometry of HR 7224
plotted with the ephemeris
HJD (light maximum) 
. The FCAPT
observations are plus signs while Winzer's V observations are
closed squares
Figure 4: Differential Strömgren uvby FCAPT photometry of HD
200311 plotted with the ephemeris HJD (maximum) 
Tables 2-5 present the observations along with their yearly and total means and standard deviations. No corrections have been made for neutral density filter differences among each group of variable, comparison, and check stars. For each star I plotted my data to see if it approximately confirmed the best published period. Then I used the Scargle periodogram (Scargle 1982; Horne & Baliunas 1986) on my data which was for each star, except for 25 Sex, the most extensive data set. I adjusted the period to make the photometric data coincide as well as possible in phase with published observations.
