We observed 9 fields in M 31 during a period of 25 days in the fall of 1993 (see Fig. 1 (click here)). The observations were performed using both the 2.5 m Isaac Newton Telescope (INT) at the Observatorio de Roque de los Muchachos, La Palma, and the 1.3 m McGraw-Hill telescope of the Michigan-Dartmouth-MIT (MDM) Observatory at Kitt Peak. The observations at the INT were performed between Sept. 9 and Sept. 17, while those at MDM were performed between Sept. 24 and Oct. 4, 1993.
The observations at the INT were performed using the Ford/Pennypacker 20482 CCD and a Kitt Peak V filter. For the f/7.5 focus of the INT, this CCD has a pixel scale of 0.367 arcseconds per pixel, giving the 20482 CCD a field of view of 12.5 arcminutes. The observations at MDM were performed using the 20482 Tektronics CCD known as "Wilbur'' (Metzger et al. 1993) at the f/7.5 focus station of the 1.3 m telescope with a Kitt Peak V filter. The CCD was read out with a 2 2 pixel binning factor, giving a pixel scale for this setup of 0.637 arcsec per pixel for a total field of view of roughly 10.9 arcminutes, similar to that of the INT observations.
The weather at both sites was good for most of the allotted period of time: Of the 20 total nights allocated to this project, four (Sept. 9, 17, 24, and 30) were lost to weather or equipment problems, several of the nights at both sites were photometric, and the rest of the nights had occasional minor clouds. A small amount of clouds was not a severe problem because differential photometry was used to determine the throughput for a given image. However, on the nights near full moon (Sept. 30), small amounts of cloud coverage increased the sky background drastically, and reduced the effective sensitivity. The measured seeing at the INT site ranged from 0.8 to 2.0 arcseconds, while that at the 1.3 m MDM site was in the range 1.2 to 2.2 arcseconds.