Perhaps the greatest lacuna in the WDS is the lack of good photometry for many of the wider systems. With a CCD camera, it is possible to measure magnitudes for double stars in some or all of the standard wavebands such as B, V, R and I. (U can be attempted if the CCD front window is coated with a layer of ultraviolet transmitting material but this can be quite expensive.) Colours are defined such as B-V, V-R and R-I and are easily calculated from the individual magnitudes in those particular wavebands. Required filters can be made up from commercially available glass such as that made by Schott. For further information see the articles by P. Boltwood9,10 (contact e-mail: [email protected] fernbank.com).
Doubtless, there are many variable components yet to be discovered and in the case of double stars the great advantage is that there is a built-in comparison already available for doing differential photometry.
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