standard filters but the blue one had a mean wavelength similar to Johnson $V$. The camera covers a field of about 0.5 square degree on the sky with a pixel scale of 0.62 arcseconds. The whole cluster could thus be observed with one observation, and most of the cluster was on one CCD of the MACHO camera (there are four CCDs per filter band). Observations were obtained once to twice a week. A few frames were lost due to technical problems or bad seeing conditions. Our monitoring came to an early end after about five months when Mount Stromlo Observatory was destroyed by a bush fire. Altogether we collected 15 useable frames over this time span. All observations were done in queue observing mode.

For the determination of light curves and the detection of variables, only the blue frames were used. The light amplitude of long period variables is typically larger in the blue than in the red (e.g. Fox [@fox82]) making the detection of variables and the determination of periods easier. Furthermore, many bright stars on the red frame were over-exposed and thus not useable. The blue detector had an area of bad pixels as well as a few 