Arp 166 consists of NGC 750 (PGC 7369, UGC 1430, VV 189a and others) and NGC 751 (PGC 7370, UGC 1431, VV 189b and others), the two interacting elliptical galaxies at the top left. Members of Arp’s ‘Diffuse filaments’ class, these are located approximately 219.5 million light-years away in Triangulum.
The elliptical galaxy with the faint halo at the bottom right is NGC 736 (PGC 7289, UGC 1414 and others). The somewhat edge-on spiral above it and to the left (east) is NGC 740 (PGC 7316, UGC 1421 and others).
Luminance – 24x600s – 240 minutes – binned 1x1
RGB – 8x300s – 40 minutes each – binned 2x2
360 minutes total exposure – 6 hours
Imaged January 14th, 15th and 17th, 2018 from Dark Sky New Mexico at Rancho Hidalgo (Animas, New Mexico) with a SBIG STF-8300M on an Astro-Tech AT12RCT at f/8 2432mm.
LRGB - https://www.flickr.com/photos/dcrowson/38458879100/sizes/l