Taurus Tunable Filter: A flexible approach to narrowband imaging

The Taurus Tunable Filter (TTF) is a tunable narrowband interference filter covering wavelengths from 6300 Angstrom to the sensitivity drop-off of conventional CCDs (similar to 9600 Angstrom), although a blue 'arm' (4000-6500 Angstrom) is to be added by the end of 1997. The TTF offers monochromatic imaging at the Cassegrain foci of both the Anglo-Australian and William Herschel Telescopes, with an adjustable passband of between 6 and 60 Angstrom. In addition, frequency switching with the TTF can be synchronised with movement of charge (charge shuffling) on the CCD, which has important applications to many astrophysical problems. Here we review the different modes of TTF and suggest their use for follow-up narrowband imaging to the AAO/UKST Galactic Plane H alpha Survey.