| Function | Value |
|---|---|
| Location | Right Nasmyth platform, Keck II; removable from focus |
| Layout | Two cameras fed from common collimator |
| Rotator | 540 degrees rotation |
| User access | Slit masks, all gratings and 2 user filters/side |
| Guiding system | Two guiders; ~5 arcmin2 field in each |
| Telescope focus | Guiders allow continuous monitoring |
| Flexure | Goal is <0.1 px over typical integrations |
| Spectrograph flexure control | Active optic with closed loop feedback |
| Focal plane flexure control | Rigidly attached reticles for guiders |
| Slit masks | 10 per side; matched to focal plane curvature |
| Slitlet options | Slitlets of arbitrary shape, size and orientation |
| Dispersive elements | 6-in x 8-in and 8-in x 12-in gratings |
| Imaging option | Silvered flat mirror replaces grating |
| Filters for each camera | 6.5 x 6.5-in glass filters; 7 slots for B,V,R,I, "clear," and 2 user |
| Collimator focal length | 86.50-in |
| Camera focal length | 15.00-in |
| Beam diameter | 6.33-in for 10.95 m primary; 5.79-in for 10.02 m vignetting radius1 |
| Monochromatic f/ratio | f/2.358 11.00 m primary; f/2.586 for 10.02 vignetting radius1 |
| Polychromatic f/ratio | f/ 1.29 |
| Scale at detector | 0".00759 um^-1 ; 0".1193 per 15um px |
| Angular field radius of camera | 11.40 degrees |
| Typical camera image quality | B band imaging: 30 um RMS (0".20 FWHM) |
| ........ | V-->I band imaging: 20 um RMS (0".13 FWHM) |
| ........ | Spectroscopy2 : 20um RMS (0".13 FWHM) |
| Camera glass transmission | 91% for l> 5200 A |
| ........(in blue) | 50% at 3900 A; 82% at 4400 A |
| Total camera throughput | 83% at l > 5200 A (inc. coatings and transmission) |
1 The vignetting radius of the primary mirror is that circle that contains all tips of the primary mirror segments except the 6 outermost ones. It is 10.02 m in diameter. The light beyond the vignetting radius is 4.5% of the total area of the unobscured primary, or 0.75% per tip. The vignetting radius has been used to simplify various vignetting calculations.
2 Averaged over all field angles for an object at the middle of the slit and for A 4400-11000 A.