Sharpless 157, sometimes referred as the Lobster Claw Nebula, is an emission nebula in the constellation Cassiopeia, at a distance of approximately 11050 light years (3390 parsecs) from the Earth. The predominantly yellow part of the nebula is a very large H II region that is ring-shaped by the stellar wind of several giant stars, including the bright and very young Wolf-Rayed star WR 57. The small bright region at the left and up of center of the image is Lyn's Bright Nebula 537 (LBN537 or Sharpless 157a). The blue colored regions at the right part of the image mainly consist of highly ionized oxygen (OIII) and other gases. The small open star cluster NGC 7510 is located at the bottom right part.
Imaged at the Skopje city center (Bortle scale 8) on 17, 18, 19 and 20 October 2020.
Imaged using Meade 115 mm triplet (reduced focal length 646 mm), ZWO ASI1600MM Pro, (Gain: 139) at -20 Celsius Degrees; Guiding: ZWO ASI174MM Mini with OAG; AsiAir Pro 1.5; iOptron CEM40EC, SII: 22x600", H-alpha: 54x600", OIII: 30x600" (total integration time 17.7 hours). Image processing: PixInsight 1.8.8-5.
Higher resolution image and more technical details available at: https://www.astrobin.com/mqaled/