Grating Spectrograph Requirements
Fundamental
- R??= 2 tan?B(d/D) =l/Dl
- ? is the angle on the sky subtended by the entrance slit
- Where ?B is grating blaze angle
- D telescope diameter
- d spectrograph beam size
Let a= ?B ~36o
- R??~ 100,000 requires a 0.3-0.5 meter aperture spectrograph with AO quality images
- Can beat size down with echelles but MOS & IFU use limited
Back to the future: wavelength multiplexed FTS?