To appear in the Sept 2000 Encyclopaedia of Astronomy & Astrophysics, MacMillan and Institute of Physics Publishing
Abstract. While tunable filters are a recent development in night
time astronomy,
they have long been used in other physical sciences, e.g., solar physics,
remote sensing and underwater communications. With their ability to tune
precisely to a given wavelength using a bandpass optimized for the
experiment, tunable filters are already producing some of the deepest
narrowband images to date of astrophysical sources. Furthermore, some
classes of tunable filters can be used in fast telescope beams and
therefore allow for narrowband imaging over angular fields of more than a
degree over the sky.
Table of Contents