2 Observations

We observed AU Ser photoelectrically, using the 1-meter reflector equipped with an EMI 6256 photomultiplier of the Yunnan Observatory, China, in three sets of two nights in April 1991, April 1992 and May 1995, respectively. The two filters employed are the following: a corning 5030 of stock thickness cemented with 2 mm Schott GG-13 for the blue region, and a corning 3389 of stock thickness for the yellow region.

We adopted the same comparison and check stars as those used by Binnendijk except for the 1991 observations in which they were shown in the finder chart in Li et al. (1992). The procedures of extinction corrections and of transferring into the UBV system were made. The probable error of a single measurement was estimated to be 0.015 mag for the 1991 observations, 0.012 and 0.016 mag for V and B band in 1992, and 0.016 and 0.017 mag for the two bands in 1995. The Heliocentric Julian Days at the start and at the end of the observation runs and the numbers of observations for each color are given in Table 1. The observations in 1992 and 1995 are listed in Table 2a and 2b for yellow and blue light respectively, while those in 1991 have been published in Li et al. (1992). The normal points producing the light curves in Fig. 2 can be found in Table 3 through 5. All tables are presented in electronic form.