SDSS Technical Information Summary

For a more thorough explanation of the Sloan Digital Sky Survey, please consult the SDSS Project Book.

Photometric Survey

• North Galactic Cap: 10,000 square degrees
• South Galactic Cap: 3 strips, each 2.5 degrees wide and about 90 degrees long. The central strip will be scanned multiple times during the survey.
• Pixels are 0.40 arcsec; the optical system delivers 0.8 arcsec images.
• The following table gives limits for point sources on the AB system:
  

  filter	lambdac (Å)	delta lambda (Å)	S/N = 10	saturation
  u'	3543	567	21.4	12.1
  g'	4770	1387	22.6	14.1
  r'	6231	1373	22.3	14.1
  i'	7625	1526	21.7	13.8
  z'	9134	950	20.1	12.3

• Photometric calibrations are enabled by a dedicated 20-inch Photometric Telescope (atmospheric extinction, calibration of fainter stars with respect to brighter fundamental standards).
• Astrometric calibrations are enabled by special CCDs in the focal plane of the 2.5-meter telescope, capable of measuring standard stars in the range 8.3 < r' < 16.5.
• Data products include: merged 5-band catalogues of image parameters (position, flux, size, profile); "atlas images" (cut-out pixel maps around each detected object); link to spectrum (if available).

Spectroscopic Survey

• Same area as for Photometric Survey
• Sources constituting complete samples (in the sense that the selection criteria are independent of the local density of sources on the sky, with the restriction of 55-arcsec closest separation):
  

  900,000 field galaxies (r'_lim ~ 18.2), median redshift 0.1

  100,000 color-selected luminous red galaxies, volume-limited to z ~ 0.4

  100,000 color-selected quasars (g'_lim ~ 19.2)

• Spectral range 3900 - 9100 Å (2 channels split at 6000 Å w/dichroic)
• Spectral resolution lambda/(delta lambda) = 2000
• Fibers project to 3 arcsec on sky
• 640 fibers per field, 45 minute exposure
• S/N > 13 per Å (typical for faint sources)
• Data products include: one-dimensional flux-calibrated spectrum (4096 pixels); derived redshift (separately for emission lines and absorption lines); line list; link to photometric and astrometric data; information detailing why this object was selected as a spectroscopic target.