The EMIR optical system

EMIR is a multiobject intermediate resolution near infrared (1.0 - 2.5 microns) spectrograph with image capabilities to be mounted on the Gran Telescopio Canarias (Observatorio del Roque de los Muchachos, La Palma, Spain). EMIR is under design by a consortium of Spanish, French and British institutions, led by the Instituto de Astrofisica de Canarias. This work has been partially funded by the GTC Project Office. The instrument will deliver images and spectra in a large FOV (6 X 6 arcmin), and because of the telescope image scale (1 arcmin equals 52 mm) and the spectral resolution required, around 4000, one of the major challenges of the instrument is the optics and optomechanics. Different approaches have been studied since the initial proposal, trying to control the risks of the instrument, while fitting the initial scientific requirements. Issues on optical concepts, material availability, temperature as well as optomechanical mounting of the instrument will be presented.