Abstract
In just two years, the OSIRIS tunable filter spectrograph on the 10 m GTC will herald a new era in spectrophotometric imaging, from 350 nm to 1 μ m. Like its forebear, the TTF at the Anglo-Australian Telescope (AAT), OSIRIS will offer a wide variety of observing modes linked to charge shuffling in order to achieve exquisite differential imaging. In some respects, simply repeating the many science cases conducted at the AAT will lead to advances in a number of fields. This is all but guaranteed by the better apparatus, observing conditions and larger aperture. However, the expected improvement in sensitivity suggests many new avenues: large surveys of extended sources, absorption line imaging, time series and coronographic imaging, to name a few. OSIRIS will provide some of the deepest photometric ``diffuse light'' images to date, much better than what can be achieved with an integral field spectrograph, and over a much wider field of view.
