HST WFPC2/PC F555W a) and F814W b) images of the site of SN 2005at. The source which we associate with the SN is indicated by the tick marks, the extended sources A and B are also shown. The red circle shows the transformed position of the He ii source (Sect. 6.1). The F555W−F814W c) image has been Gaussian smoothed for illustration purposes. The different colours of sources A and B are evident. The scale and orientation of all three panels are identical and indicated in the panels on the right.