TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5511 SUBJECT: GRB 060904B: Optical observations at Crni Vrh DATE: 06/09/04 05:40:46 GMT FROM: Jure Skvarc at OCV J. Skvarc on behalf of PIKA observing program at Crni vrh Observatory reports: We observed optical counterpart of GRB060904B (Swift trigger 228006) using 60 cm robotic telescope at Crni Vrh Observatory, Slovenia. A variable object was detected at ra=03:52:50.52, dec=-0:43:30.9. The coordinates are derived using UCAC-2 catalog. 1-sigma accuracy of these coordinates is about 0.2 arcseconds. Alternating exposures using R and B filters were taken, starting 45 s after the trigger was received. The following table contains start of exposure (2006-09-04 UT), exposure duration in seconds and magnitude: R filter: 2:32:02 90 18.21 2:37:32 90 17.01 2:43:03 90 17.11 2:48:33 90 17.79 2:54:03 90 18.19 2:59:37 90 17.66 3:08:27 180 17.78 3:13:23 180 17.79 3:17:50 180 17.99 B filter: 02:34:02 180 18.32 02:39:32 180 17.51 02:45:03 180 18.56 02:50:33 180 18.81 The magnitudes are derived using comparison stars from the USNO A2 catalog. Estimated 1-sigma statistical uncertainty is 0.02 for R and 0.04 for B filter. ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.