A very wide field spectrograph may encounter optical challanges not unlike those faced by the GMOS spectrograph. As a starter, the GMOS optical design may provide a basic idea of how our spectrograph may look like. The tunable nature of the Volume Phase Gratings can allow a reconfigurable spectrograph, in which the grating can be tilted and the camera angle adjusted, to utilize a single grating element for a variety of dispersions and to optimize the diffraction efficiency for a particular wavelength. He also gave some science drivers for a more modest resolution spectrograph. Spectral coverage would be minimal but centered on the Ca II H and K lines.
Hydra can perform observations of the brighter sampling of stars.
Low efficiency of Hydra will limit the achievable magnitude of these surveys. George Jacoby discussed the science of planetary nebulae in the buldge of M31. Spectral coverage is a driver with coverage of the 3727 line considered a requirement out to beyond 7000 Ang. Spectrophotometry over this range in wavelength will require an ADC to compensate for atmospheric dispersion. Resolution of better than 7 Ang.