This is a small section of the galaxy cluster Abell 1367, centered on NGC 3842.
There is a possible supernova just above NGC 3842 that was not noticed until a year
after it was taken. It does not appear in a later image, the
Digital Sky Survey
or an image from the Hubble Space Telescope
The left image was taken on June 26, 1997 approximately 11PM CDT (4:00 June 27 UT). If you have any images of this galaxy from that time, please check them and let me know if this object is present. This is a real object. It appears in three other raw images taken the same night.
The right image was taken in 1999 using the same telescope and camera.