{
  "bibcode": "2006GCN..4977....1K",
  "body": "M. Koppelman (Starhouse Observatory and University of Minnesota) reports on\nbehalf of the AAVSO International High Energy Network on optical observations\nof GRB060418 (GCN #4966, Falcone et al.) and its reported optical afterglow\n(GCN #4968, Melandri et al.; GCN #4971, Nysewander et al.; GCN #4972, Cobb\net al.):\n\nKoppelman reports the following Rc-band measurement:\n\n03:46:20 UT  Rc=16.47+/-0.14.\n\nRc magnitudes are untransformed and differential with respect to a \ntwo-star ensemble with USNO B1.0 stars 0863-0300553 (R=14.86) and \n0864-0294924 (R=14.22). Scatter in the check star was 0.05 mag.  A \ndetailed report of these observations follows at the end of this report.\n\nM. Nicholson (International Consortium of Robotic Astronomical Researchers)\nreports V-band observations of this afterglow approximately three hours after\nthe burst.  Analysis of these observations is continuing.\n\nThe AAVSO thanks the Curry Foundation for their continued support of the\nAAVSO International High Energy Network.\n\nRc-band observations by M. Koppelman, Starhouse Observatory:\n-----------------------\nName: Michael Koppelman\nemail: michael at aps.umn.edu\nObserver: Michael Koppelman (KMP)\nSite: Starhouse Observatory\nLocation: Cologne, MN\nLatitudeLongitude: 45N 93W\nElevation: 800'\nScope: Newtonian 0.212m\nScopeFocalRatio: f/3.9\nCCDVendor: SBIG ST-7XME\nCCDDetector: Kodak KAF-0402ME\nCCDSize: 765x510\nCCDPixelScale: 2.26\"/px\nCCDFOV: 30x20\nObject: GRB060418A\nObsDate: 2006-04-18\nObsMidPointTime: 2006-04-18 03:46:22\nTimePerFrame: 60, 120 and 180s\nNumberOfFrames: 10\nFilters: Rc\nProcessing: bias, dark, flat\nSeeing:\nLimitingMag:\nSky: Good\nafterglowmag: 16.47\nafterglowerr: 0.14\ncompstars: B1.0\t0863-0300553\t and 0864-0294924\nReport: I observed the afterglow at high air mass (~5) with an Rc filter.\nPlate solution yields a position of 15:45:42.54 -03:38:21 with an error\nof about 1\". The afterglow is visible on 1 of 10 images but reliably\ndetected above the sky background on 2 other images for a total of 3\npositive detections.\n\nJD             Rc      Err\n2453843.6530   16.44   0.39\n2453843.6600   16.57   0.22\n2453843.6621   16.37   0.22\n\nRc magnitudes are untransformed and differential with respect to a\ntwo-star ensemble with USNO B1.0 stars 0863-0300553 (R=14.86) and\n0864-0294924 (R=14.22). Scatter in check star was 0.05m.\n\nFits images and photometry available upon request to michael at aps.umn.edu.",
  "circularId": 4977,
  "createdOn": 1145389695000,
  "email": "aavso@aavso.org",
  "subject": "GRB060418: Optical Observations",
  "submitter": "AAVSO GRB Network at AAVSO  <aavso@aavso.org>",
  "eventId": "GRB 060418"
}