Arp 172 is a pair of obviously interacting galaxies in the Hercules Cluster that Arp put in his category for galaxies with diffuse counter tails. Tidal plumes weren't understood at the time so this is Arp's description of its visual appearance. Some sources consider both galaxies as IC 1181 with the northern one IC 1181A and the southern IC 1181B. Others consider it 1181 only the southern galaxy and IC 1178 either the northern or both. NED classifies the northern galaxy as S0:- pec? and the southern as SAB(rs)0/a. Both were discovered by Lewis Swift on June 3, 1888.

This data was taken on September 13, 2007. I didn't have the tools to do it justice back then. I need to reshoot this one. It also contains ARP 71, Arp 122 and Arp 272. Details are in the annotated image. The annotated image shows details on many other galaxies in the cluster and beyond it.

Arp's image: http://ned.ipac.caltech.edu/level5/Arp/Figures/big_arp172.jpeg

14" LX200R @ f/10, L=6x10' RGB=3x10', STL-11000XM, Paramount ME