Table 1: Estimated Physical and Optical Characteristics
Location Right Nasmyth platform, Keck II; removable from focus
Layout Two cameras fed from common collimator
Rotator 740 deg rotation
User access Slit masks, all gratings and all filters
Guiding system One guider; ~10 sq amin FOV; slit-viewing and offset
modes are both available
Spectrograph Two-coordinate beam-steering with closed-loop feedback
flexure control
Flexure Goal 0.25 px rms motion over typical integration
(with flexure control system on, 2px rms open loop)
Slit masks 13 in cassette; cylindrical radius of curvature
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; 3 slots
Imaging option Silvered flat mirror replaces grating
Filters 6.5 x 6.5-in glass filters; 7 slots; BVRI, "clear,"
and 2 "user" slots
Collim. 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 primary
Monochromatic f/ratio f/2.358 for 11.00 m primary; f/2.586 for 10.02 m primary
Polychromatic f/ratio f/1.29
Scale at detector 0.00759 asec/mu; 0.119 asec per 15mu px
CCD detector array 8192 x 8192 px (15 mu px); 2 x 4 mosaic of 2K x 4K CCDs
Angular field radius 11.40 deg of camera
Camera glass xmission 97%for lambda > 5200A; 88% at 3900A; 93% at 4400A
Total camera xmission 85% at lambda > 5200A; 77% at 3900A (including coatings
throughput and transmission)

Spectroscopic image quality is averaged over all wavelengths and field angles for an object at the middle of the slit.

Table 2: Estimated Imaging Performance
Field shape Rectangular with 2 lopped-off corners;
sliver out of long side
Outer dimensions of rectangular field 16.7 amin x 5.0 amin
Area lost to CCD mosaic gaps 0.4 amin x 5.0 amin
CCD pixel scale 0.119 asec per px (15mu px)
Wavelength range (imaging) 4100A -- 11,000A
Standard filters1 BVRI + 2 user filters
Throughput at 6000A2 40% (including telescope)
Image size B band (0.5 asec seeing) 0.56 asec FWHM (including telescope
V-->I bands 0.54 asec FWHM (including telescope
Expected count rate3 800 e- per sec in V band at 21.0 mag
Mode changes 30 sec changeover between imaging
and spectroscopy

1 Slightly redshifted B band with blue edge at ~4000A.
2 End-to-end throughput including telescope and assuming CCD QE=0.6 and all reflecting surfaces are silver coated. No filter or atmosphere included.
3 V mag is light entering telescope. Rate is through standard V filter.

Table 3: Estimated Spectroscopic Performance
Total slit length 16.7 amin
Usable slit length1 16.3 amin
Total number of slitlets 85 10 asec slitlets with 1.5 asec gaps
CCD detector scale 0.119 asec per px (15mu px)
Wavelength range (spectra) 4100A -- 11,000A
Order blocking filters TBD
Slit widths User selectable by choice of mask; long-
slits will provide variety of fixed widths
Design slit widths 0.75 asec nominal, 0.5 asec good seeing
Current gratings (all 6 x 8 in) 600 l/mm (7500A blaze): 900 l/mm (5500A
blaze); 1200 l/mm (7500A blaze)
Number of grating slots 3 slots available
Corresponding dispersions 0.65A/px, 0.44A/px, and 0.33A/px
Spectral lengths (8000 px) 5300A, 3840A, and 2630A
FWHM resolutions for 0.75 asec slit 3.5A, 2.1A, and 1.1-1.6A
Throughput at 6000A2 29% (including telescope)
Count rate at 6000A 1.0 e- per sec at V = 21.0
S/N on faint stellar objects in one hour3 5:1 for V = 24.0; 12:1 for V = 23.0;
21:1 for V = 22.0

1Slit length subtended by detector pixels.
2 End-to-end throughput including telescope assuming CCD has QE=0.6 and all reflecting surfaces are silver coated.
3 S/N per pixel for 3600 s integration, 0.75 slit, on point source with 0.7 asec seeing at 5500A and 0.65A/px (600 l/mm grating). V is magnitude of light going through slit. Assumed V sky brightness is 21.25 mag/asec.