TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3980 SUBJECT: GRB050915, optical observations DATE: 05/09/15 13:38:42 GMT FROM: Arne A. Henden at AAVSO P. Kilmartin and A. Gilmore (Canterbury) report on behalf of the AAVSO International High Energy Network: We observed the localization of the Swift burst GRB050915 (Grupe et al. GCN 3977) with the 60cm OCS telescope of Mount John Observatory. 600 seconds of stacked unfiltered observations with mipoint at 050915.542 (1.6hrs after the burst) reached a limiting magnitude of CR=18.0 estimated from USNO-A2.0 stars. No new object is present by comparison with DSS2-R. Observations are continuing. The AAVSO thanks the Curry Foundation for their continued support of the AAVSO International High Energy Network.