An rms accuracy of 0.003 magnitudes was reached during each 60 second V-band observation of the 6.5 magnitude star. This accuracy was achieved by defocussing the APT so that images were 15 pixels across, thereby reducing the effect of intrapixel sensitivity variations. The advantage of the APT for this observation is that bright standard stars could be measured on the same exposure. A subset of the images is being used for an undergraduate experiment in image analysis by Michel Breger in Austria. Studies of stellar activity are useful for understanding the structure and heating of stellar atmospheres, and can help us learn more about stellar rotation, evolution, and angular momentum loss.
Young stars possess the most intense activity.
The most energetic stellar flares observed occur on pre-main sequence stars, and flare activity is prevalent in many open clusters. Pre-main sequence stars show relatively large photometric variations indicative of starspots covering significant fractions of their surfaces, and chromospheric plages similar to those in solar active regions have been identified. With its wide field of view, and facility for long-term photometric monitoring of cluster stars in B, V, R and I colours, the APT is well suited to photometric studies of activity in star clusters. In addition, its observations can complement spectroscopic investigations done with other telescopes. Obtaining flares light curves, energies and statistics, to resolve present ambiguities, and provide data for studies of the relationship between flare activity and the evolution of low-mass stars.