Spectrograph parameters and description
Each spectrographic exposure collects spectra from 640 points on the focal
plane, most of them corresponding to objects. An aluminum plate with holes
drilled at the desired locations fixes the points from which spectra will be
gathered. When prepared for observation, this plate (usually called a plug
plate) is mounted on a cartridge that can be quickly mounted and dismounted
from the telescope. Optical fibers plugged into the holes in the plate carry
light from the focal plane to slitheads attached to the cartridge. Each of
the two slitheads accept light from 320 of the total of 640 optical fibers,
and correspond to a spectrograph permanently mounted on the back of the
telescope. Mounting a cartridge on the telescope brings the plug plate to
Cassegrain focus and mates each slithead to its corresponding spectrograph.
Each of the two spectrographs collect spectra on 2 SITe/Tektronix 2048 by
2048 CCDs, one covering a wavelength range of 3800 Å to 6100 Å, and the
other from 5900 Å to 9100 Å.
A detailed description of the spectrographs can be found in the technical summary and in the project
book. This page summarizes the most important information needed to
understand the data it produces.
|4, 2048 × 2048, SITe/Tektronix, 49.2mm square
|3800-6150Å (blue), 5800-9200Å (red)
|Number of fibers
|320 × 2
|Hg, Cd, and Ne arc lamps, rms error of 0.07 pixels (10 km/s)
|Standard stars in each field, tied to colors observed with the
|ranges from 1850 to 2200
|Exposures are taken until the cumulative mean S/N per pixel exceeds
4 for a fiducial fiber magnitude of g = 20.2 and i = 19.9, typically
3 exposures of 15 minutes each under good conditions.
Last modified: Thu Apr 3 15:32:45 CST 2003