Mechanical challenges to implement a UV spectrograph on the GTC

CHORUS ( Canary Hybrid Optical high-Resolution Ultra-stable Spectrograph ) has been extended toward the short wavelength with a medium resolution spectrograph covering the range from 310nm to 410nm. For obvious reason this spectrograph could not stand in the Coudé room close to it high stability visible brother. The paper reports on the mechanical design used to place the long spectrograph in a rather uncommon place under the Nasmyth platform. A complex mechanical design is also necessary to avoid the last meter of fiber and implement a fully optical feeding.