TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3220 SUBJECT: GRB 050410: Early observations with Swift-UVOT DATE: 05/04/10 17:03:38 GMT FROM: Padi Boyd at GSFC P. Boyd (GSFC), V. Mangano (INAF-IASF/Palermo), S. T. Holland (GSFC), S. Hunsberger (PSU), T. Poole (MSSL), M. Still (GSFC), N. Gehrels (GSFC), K. Mason (MSSL), J. Nousek (PSU) report, on behalf of the Swift UVOT team: The Swift Ultra-Violet/Optical Telescope (UVOT) began settled observations of the field of GRB 050410 (Parola et al; GCN 3218) at 12:46:17 UT on 10 April 2005. This is immediately after the target exited the Swift Earth-limb constraint, 1912 seconds after the BAT trigger. The first UVOT data arrived via TDRSS; it is a 100s V image starting immediately after spacecraft settling, binned 8x8 (pixel size 4.x4. arcsec) centered on the BAT position, and 5.33 arcminutes per side. Mid-exposure time was 1962 s after the trigger. A comparison against the Digitized Sky Survey reveals no new sources within the BAT and XRT error circles down to a 5-sigma background limit of V = 18.5 with a systematic uncertainty of 0.1 mag (due to uncertainties in the photometric zero point). This limit is based upon preliminary flight calibrations.