Abstract
OSIRIS is the Spanish Day One instrument for the GTC 10.4-m telescope. OSIRIS is a general purpose instrument for imaging, low-resolution long slit and multi-object spectroscopy (MOS). OSIRIS has a field of view of 8.6×8.6 arcminutes, which makes it ideal for deep surveys, and operates in the optical wavelength range from 365 through 1000nm. The main characteristic that makes OSIRIS unique amongst other instruments in 8-10m class telescopes is the use of Tunable Filters (Bland-Hawthorn & Jones 1998). These allow a continuous selection of both the central wavelength and the width, thus providing scanning narrow band imaging within the OSIRIS wavelength range. The combination of the large GTC aperture, large OSIRIS field of view and availability of the TFs makes OTELO a truly unique emission line survey.
