SIMBAD references

Photometric data were obtained for a set of known QSOs in five bands with a filter system for the purpose of testing the ability of the SDSS system to separate QSO colors from the colors of the stellar locus. Data were obtained from two similar telescopes and camera systems, and were intercompared. The F stars BD +26 degrees 2606 and BD +17 degrees 4708 were used as primary standards to set the zero pints for the rest of the observed objects. The standard star magnitudes were found to be in reasonable agreement with the theoretical predicted magnitudes, and the QSO colors were well separated from the stellar locus, defined by random stars in the QSO fields.