Sharpless 2-170 is a very large and faint emission nebula. The image above has been down sampled 0.5x.
Sh2-170 is in the vicinity of the Cassiopeia OB5 supershell. The sole exciting star of Sh 2-170 is DM+63 2093, an O8 V star of 31 solar masses. (galaxymap.org)