1995BaltA...4..527B

I discuss the advantages of CCD detectors for the type of science done with the Whole Earth Telescope. The advantages are illustrated by my experiences in a collaboration with R. Ciardullo involving photometric monitoring of planetary-nebula nuclei (PNNs). CCDs combine high quantum efficiency with the ability to measure the target, any surrounding nebulosity (or close companions), several comparison stars, and the sky background, all strictly simultaneously. One can therefore monitor faint stars under non-photometric conditions, in bright moonlight, and well into twilight; the total coverage possible in a photometric campaign is extended significantly, and the campaign can be done at full moon in order to compete more successfully for telescope time. Scientific results from our own collaboration include discoveries of close-binary PNNs, a new class of irregularly variable central stars, and seven new nonradially pulsating PNNs. To date we have organized multi-site asteroseismological CCD campaigns on two of the new nonradial pulsators, NGC 1501 and Sand 3.