SDSS performs multi–object spectroscopy using two bench spectrographs attached to the SDSS telescope and fed with 640 optical fibers. The other ends of these fibers are plugged into a pre–drilled aluminum plate that is bent to follow the 3–degree focal surface of the SDSS telescope. The reader is referred to Smith et al. (2002), Blanton et al. (2003) and Pier et al. (2003) for more details about the SDSS.

In this way, the SDSS plans to image the northern sky in 5–passbands as well as obtaining spectra for $\sim10^6$ objects. In addition to the large amount of the data being collected, the quality of the SDSS data is high, which is important for many of the scientific goals of the survey. For example, the SDSS has a dedicated Photometric Telescope (PT; Hogg et al. 2001) which is designed to provide the SDSS with a global photometric calibration of a few percent over the whole imaging survey. Also, SDSS spectra are spectrophotometrically calibrated.

The SDSS in now in production mode and has been collecting data for several years. As of January 2003, the SDSS had obtained 4470 deg$^2$ of imaging data (not unique area) and had measured a half million spectra. 