This data is part of a paper in progress, but I am posting it so that other people working on the SDSS can use it as an aid to constructing the survey. My co-authors are Gordon Richards, Michael Richmond, and Xiaohui Fan. I am currently applying for 3.5 meter time to look at some of the outliers from the stellar locus, including those listed below.
We present a catalog of over 2000 stars, QSOs, and galaxies in five optical passbands (u*, g*, r*, i*, and z*) that will be used by the Sloan Digital Sky Survey. Of these, more than 1600 are from a uniform sample with r* < 19.5, selected from 15 fields covering half a square degree. About half of the objects have a measured u* flux. The statistical error in the photometry is typically a few percent. The systematic error is less than about 10 percent. The data was obtained on the USNO 1-m in Flagstaff, Arizona.
The catalog will be used to tune selection algorithms that will select spectroscopic targets from the photometric data produced by the Sloan Digital Sky Survey. We also supply and ascii version of the catalog.
We have color plots for all 1630 objects in the uniform sample. Only objects with both colors measured were included in individual color plots. The uniform sample is magnitude limited at 19.5 in r*, but the individual plots include additional incompleteness due to detection limits in the various bands. Approximate limiting magnitudes are u* > 21.5, g* > 21, i* > 20.5, z* > 19.0. Black dots are point sources, cyan dots are extended sources, and red dots are known QSOs measured in this data set. The magenta line shows a fit to the stellar locus. Only about half of the objects (the bluer ones) were detected in u*.