A Canadian wide-field optical spectrograph for a 30-m telescope

A wide-field low-resolution multi-object optical spectrograph suitable for a 30-m F/15 telescope is described. The effort to build a 30-m class telescope is gaining momentum. Many science cases for such a telescope make the need for a wide-field seeing-limited spectrograph a high priority. Our concept comprises four identical instruments placed symmetrically around the optical axis of the telescope, this allows smaller dimensions for the spectrographs and their components. Each instrument is placed in one quadrant of the telescope focal plane; a space at the center of the field is free for other instrumentation. Using a dichroic beam-splitter each instrument feeds a "red" and "blue" camera. The total field is 81 square arcmin, the wavelength range covers simultaneously 310 nm to 1000 nm and the spectral resolution (R) is 300 to 5000. The instruments are designed for vertical mounting at a Nasmyth focus to avoid gravity vector changes and reducing mechanical flexure problems during observation. The layout also allows access to internal components for maintenance. The design offers advantages for the location of a slit mask and filters. The instruments can also be used for imaging. Optical and opto-mechanical models and analyses are presented with specifications and expected performance.