The cluster observations are simple: just point and shoot. There are however a number of points to keep in mind for the time series observations:
Focus: Contrary to the usual way of ``oscillation photometry'' which involves de-focusing these observations should be as close to focus as possible in order to ensure high spatial resolution. The telescope focus may vary as a function of zenith distance and temperature. Therefore, keep an eye on these parameters (and the seeing monitor) in order to estimate when the focus has to be changed.
Saturation/Exp. times: The stars of primary interest for these observations are
red giant branch (RGB) stars, of which the brightest have
therefore we do NOT want these stars to be
saturated. The DFOSC based finding chart identifies stars which
we are interested in. The exposure times must be set such that
these do not saturate. We currently estimate that exp. times
near 40 sec. are possible - BUT THIS MUST BE CHECKED FROM
ACTUAL OBSERVATIONS.
Some of the stars brighter than the primary targets will saturate. We expect, however, that many of these stars will show oscillations as well although on a much longer timescale than the primary targets. Therefore we should include one or two exposures, with an integration time so short that the brightest giants do not saturate, for every 20 exposures at the nominal time for the primary targets. This shorter integration is probably of order 10s.
Placement on CCD: Experience shows (SRF, HK) that the highest precision differential photometry is obtained if the stars are not allowed to ``wander around'' on the CCD between exposures. Therefore once the field has been defined by the first observer we should stick to the exact field and try to put a given star in the same spot during the observations.