HORuS is a high-resolution (R=25000) spectrograph for the 10m Gran Telescopio Canarias (GTC). It collects light at the Nasmyth focal plane, shared with OSIRIS, using a 3x3 IFU (2.1x2.1 arcsec) with microlenses, into optical fibers that form a pseudo-slit at the spectrograph entrance. The light is dispersed with a 79 gr/mm echelle grating and cross-dispersed with three prisms, providing almost continuous coverage between 380 and 690 nm. In a 30-min integration HORuS gets a S/N ~ 1500, 250, 35 at 500 nm per resolution element for a V=7, 11, 15 mag solar-like star, respectively. A rudimentary exposure time calculator is available below. The grating and cross-dispersion prisms are fixed, and therefore so is the spectral coverage. In addition to the exposure time, only the CCD (4096x4096 Fairchild) binning can be chosen, with two recommended modes: no binning for very bright targets (V<9) where the readout time is not an issue (90 seconds), and 8x2 binning for fainter targets or for bright ones when the readout time (5 seconds), and the readout noise, need to be minimized. A preliminary data reduction pipeline is available.
- Preliminary Th-Ar ATLAS (PDF)