Object name: IC0391
IC 391 made my list as it fits Arp's category for 3 armed spiral galaxies. None of the three that made his list are truly 3 armed. Like IC 391 one of the arms is a disconnected arm segment rather than an arm coming off the core or a bar. Still, it looks more like it is truly 3 armed than the three in Arp's atlas to my eye. It is located in Camelopardalis 12 degrees south of the north celestial pole. Redshift measurements put it 69 million light-years distant though a single Tully Fisher measurement says 83 million but with a fairly large error bar. Still, the Hubble image of it says it is 80 million light-years away. How they determine this I don't know. Going with the 80 million light-year distance the galaxy's spiral arms span some 23,000 light-years. The outer halo is some 35,000 light-years across. This isn't a very big spiral galaxy. NED classifies it as SA(s)c. Its core is surprisingly small, almost star-like in my image.
Related Designation(s):2MASS J04572113+7811196, 2MASS J04572175+7811192, 2MASX J04572110+7811195, AKARI J0457208+781121, CGCG 0449.5+7807, CGCG 347-009, IC 0391, IC0391, IRAS 04497+7806, IRAS F04497+7806, ISOSS J04573+7812, KIG 0155, KIG 0155:[VOV2007] 024, KUG 0449+781, MCG +13-04-011, NVSS J045721+781124, PGC 016402, UGC 03190, UZC J045721.3+781126, WN B0449.6+7806, [SLK2004] 0464,