TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3246 SUBJECT: GRB 050408: SDSS Field Calibration DATE: 05/04/12 13:37:03 GMT FROM: Melissa Nysewander at UNC,Chapel Hill M. Nysewander, D. Reichart, D. Lamb, and D. York report: Using ugriz magnitudes from the SDSS DR3 and the transformation equations of Smith (2002; AJ, 123, 2121), we have calculated the UBVRcIc magnitudes of 50 sources in the field of GRB 050408: http://www.physics.unc.edu/~mnysewan/grb050408_fc.txt Systematic errors are typically 0.02 mag in the gri bands and 0.05 mag in the u and z bands. Statistical errors begin to dominate in u and z at roughly 21 mag and in gri at roughly 21.5-22 mag. All of these sources have been classified as stars by the SDSS frames pipeline; however, some of the fainter sources may be galaxies, regardless of this. Users can find the statistical and systematic error on the magnitude of any SDSS object in the field at http://cas.sdss.org/astro/en/tools/explore/obj.asp?ra=180.571087&dec=10.850506 by clicking on the "Field" button under "PhotoObj" in the column at the far left, and make their own decision about whether an object is a galaxy or a star at http://cas.sdss.org/astro/en/tools/chart/navi.asp?ra=180.571087&dec=10.850506