2. Observations and data reduction

The field centered approximately on the center of NGC 288 was monitored at Las Campanas Observatory with the 1-m Swope telescope and with the 2.5-m duPont telescope. The observational data were collected during several runs conducted between December 1990 and September 1992. The data were taken on 25 nights and on 7 nights the cluster was monitored continuously for at least 4.5 hours. Three different cameras were used: a) 1024² Tektronix CCD with scale 0.61 - TEK2 camera, 1-m telescope; b) 2048² Ford Aerospace CCD with scale 0.435 - FORD camera, 1-m telescope; c) 2048² Tektronix CCD with scale 0.23 - TEK3 camera, 2.5-m telescope. Most of data were taken with the V filter, with only occasional exposures taken in the B and I bands. We obtained a total of 462 useful images in the V-band. The exposure time ranged from 7 minutes to 10 minutes. For the prevailing number of images the seeing was better than 1.5 arcsec. A detailed log of all observations was submitted to the editors of A&A (see Appendix A).

  
Figure 1: Finding chart for NGC 288 variables. Each chart is 30 arcsec on a side with north up and east to the left

The preliminary processing of the raw data was made with IRAF. Stellar photometry was extracted using DAOPHOT/ALLSTAR (Stetson 1987) and DoPHOT (Schechter et al. 1993) programs. We followed procedures described in some details in Kaluzny et al. (1995). The instrumental photometry was transformed to the V system with the zero point defined by the data set from CTIO (Paper I).