SIMBAD references

The Whole Earth Telescope (WET) is a global network of collaborating astronomers designed to obtain very long lightcurves, uninterrupted by daylight, of variable white dwarf stars for asteroseismological analysis. Uniformity of instrumentation is a vital requirement for the success of the network. We report here on the instrument adopted as the standard WET photometer. In particular, we describe a recent addition to the design which allows older two-channel instruments to be converted to three-channel instruments, allowing continuous measurement of the sky background. This new component is a bolt-on upgrade to the existing two-channel photometers used by the WET and many others around the world. We will make the complete design (including acquisition and reduction software) available to interested parties upon request.