Anyway, marked is Supernova PSNJ12355230+2755559. Actually it is LBV PSN J12355230+2755559, a Luminous blue variable. We measured it a little brighter than 17th magnitude.
Luminous blue variables (LBVs) are massive evolved stars that show unpredictable and sometimes dramatic variations in both their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Large Magellanic Cloud. They are extraordinarily rare with just 20 objects listed in the General Catalogue of Variable Stars as SDor, and a number of these are no longer considered to be LBVs.