The Sloan Digital Sky Survey or SDSS is a major multi-filter imaging and spectroscopic red shift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico. The project was named after the Alfred P. Sloan Foundation.
The surveys were begun in 2000, and aims to map 25% of the sky and obtain observations on around 100 million objects and spectra for 1 million objects. The main galaxy sample has a median redshift of 0.1; there are redshifts for luminous red galaxies as far as z=0.4, for quasars as far as z=5; and the imaging survey has been involved in the detection of quasars beyond a redshift 6.
In the year 2006 the survey entered a new phase, the SDSS-II, by extending the observations to explore the structure and stellar makeup of the Milky Way, the SEGUE and the Sloan Supernova Survey, which watches after supernova Ia events to measure the distances to far objects.
The SDSS telescope uses the drift scanning technique, which lets the telescope fix and makes use of the earth's rotation to record small stripes of the sky. The image of the stars in the focal plane drifts along the CCD chip, instead of staying fixed as in tracked telescopes. This method allows consistent astrometry over the widest possible field and precision remains unaffected by telescope tracking errors. The disadvantages are minor distortion effects and the CCD has to be written and read in the same time.
The surveys were begun in 2000, and aims to map 25% of the sky and obtain observations on around 100 million objects and spectra for 1 million objects. The main galaxy sample has a median redshift of 0.1; there are redshifts for luminous red galaxies as far as z=0.4, for quasars as far as z=5; and the imaging survey has been involved in the detection of quasars beyond a redshift 6.
In the year 2006 the survey entered a new phase, the SDSS-II, by extending the observations to explore the structure and stellar makeup of the Milky Way, the SEGUE and the Sloan Supernova Survey, which watches after supernova Ia events to measure the distances to far objects.
The SDSS telescope uses the drift scanning technique, which lets the telescope fix and makes use of the earth's rotation to record small stripes of the sky. The image of the stars in the focal plane drifts along the CCD chip, instead of staying fixed as in tracked telescopes. This method allows consistent astrometry over the widest possible field and precision remains unaffected by telescope tracking errors. The disadvantages are minor distortion effects and the CCD has to be written and read in the same time.
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