Arp 188 has only a small apparent size due to its distance of 420 million light years, but since the galaxy shows interesting details and especially a large tidal tail, it went on my todo list. The tidal tail, with an extent of 280,000 light years, is thought to have been formed by an encounter with a smaller galaxy about 100 million years ago. There is also a distant galaxy cluster in the field with a redshift z = 0.251, which corresponds to a light travel time of 3 billion years.
Image with 12" Newtonian + QSI 660
Full field with image data:
Crop with 150% resolution: