...Institute
http://archive.stsci.edu/sdss
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...Fermilab
http://www.sdss.org
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...(NAOJ)
http://sdss.nao.ac.jp
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...Astrophysics
http://www.sdss.mpg.de
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...web
http://www.astro.princeton.edu/PBOOK/welcome.htm
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...interface
http://archive.stsci.edu/index.html
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...web
http://astro.princeton.edu/PBOOK/welcome.htm
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...systems
In fact, strictly speaking, there is not one 2.5-meter system, but six, because the detectors and filters in each CCD column are slightly different. These differences are appreciable only in the z band, which is cut off on the long-wavelength side by the detector response. While these differences must be accounted for in detail for some work, for most purposes the average response curves are sufficient.
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...calibration
Note that we only implemented the smear exposures half-way through commissioning. Table 4 indicates for each plate whether a smear exposure was actually taken.
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...chip
The situation has improved since these data were taken, as the telescope is now better collimated.
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...objects
In order to keep up with the data processing, the measure objects module of frames devotes only 20 milliseconds per object on a 1 GHz Pentium III machine.
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...question
Placeholders exist in the database for the errors on each of these quantities, but they are not currently calculated.
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...changes
Note that these isophotal quantities are the only ones which require a priori photometric calibrations before frames is run. They use a preliminary calibration, which is only accurate to 0.05 mag or so.
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...photometry
In future data releases, we expect to improve on this technique by carrying out multiple smear exposures of the fundamental SDSS standard stars.
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.

Michael Strauss
Thu Jan 30 11:15:34 EST 2003