2010CBET.2303....1N

S. Nakano, Sumoto, Japan, reports the discovery by Koichi Itagaki (Teppo-cho, Yamagata) of an apparent supernova (mag 17.3) on unfiltered CCD frames (limiting mag 19.0) taken on June 3.71 UT using a 0.60-m f/5.7 reflector (+ Bitran BT-214E camera). Itagaki then found a pre-discovery image of 2010dq at mag 18.0 on an unfiltered CCD frame (limiting mag 18.5) that he had taken on May 31.748. The new object is located at R.A. = 0:15:29.70 ± 1".7, Decl. = +17:19:41.0 ± 0".3 (equinox 2000.0), which is 17" west and 1" south of the center of NGC 57. Nothing is visible at this position on Itagaki's many past frames, including one from 2007 Aug. 20.66 (limiting mag 19.0), or on the Digitized Sky Survey. Itagaki has posted images of 2010dq at website URL http://www.k-itagaki.jp/images/psn57.jpg.