Contour plots of all five individual observations and the composite image combining the data of all epochs. The tiles are centred on the assumed core of M 15 at coordinates RA = 212958330, Dec = 12°10′01200. The circle indicates the 3σ error of the position of the core as determined by Goldsbury et al. (2010). Adopting a distance of 10.3 kpc to M 15, each tile has a physical dimension of about (20 000 AU)². Contours are ( − 5, − 3,3,5) times the rms in each individual epoch (4.7, 8.9, 4.3, 11.5, 5.8 μJy). The noise level of the composite image is 3.3 μJy.