The Lobster Claw Nebula (SH2-157) and Bubble Nebula (NGC 7635) are two striking emission nebulae located close to the border of Cassiopeia and Cepheus constellations. The Lobster Claw Nebula derives its name from the curved, segmented shapes that resemble a lobster’s pincers. It is an Ha II region of glowing ionized hydrogen excited by the intense ultraviolet radiation of nearby hot, young stars. Notably, within it lies the young Wolf-Rayet star 157, whose powerful stellar winds sculpt the surrounding gas into complex arcs and filaments.

Relatively nearby, the Bubble Nebula features a spherical bubble of gas about seven light-years across. The bubble is ‘blown’ by the fierce stellar wind of a massive O-type star (SAO 20575) at its centre. The expanding shell of gas glows where it collides with denser regions of the interstellar medium, producing a visually stunning contrast of colours.

Notwithstanding the spectacular nature of both of these nebulae, the image captures a myriad of other objects, which are identified in the accompanying plate solved image, notable of which are the open star clusters of M52 AKA the Scorpio Cluster and NGC 7510. Overall, the constellation of Cassiopeia is full of interesting nebulae and bright star clusters, which my second image from Castle Farm Observatory has caught in abundance.

IMAGING DETAILS
Main Objects	SH2-157 Lobster Claw & NGC 7635 Bubble Nebulae
Constellation	Cassiopea
Distance	Lobster 11,000 & Bubble 7,100 light-years
Size	Lobster 60’ x 50 (212 light-years); Bubble 15’ x 8’ (>=7 light-years)
Apparent Magnitude	Variable >=5.0
Scope	William Optics GT81 + Focal Reducer FL 382mm  f4.72
Mount & Control	ZWO AM5 + ASIair
Guiding	William Optics 50mm guide scope
	+ ZWO 120MM Mini
Camera	ZWO ASI294MM CMOS sensor
	FOV 2.87o x 1.96o Resolution 2.50”/pix  Max. image size 4,144 x 2,822 pix
EFW	ZWOx8 EFW & 31mm Chroma Ha, OIII, SII 3nm & RGB filters
Capture & Processing	ASIair, Deep Sky Stacker & PixInsight v1.9.3 Lockhart
Image Location              & Orientation	Centre = RA 23:16:22.86      DEC +60:30:51.1                         Top Left = North
Exposures	Ha x 39 + OIII x 42 + SII x 42 @ 300 sec + LRGB x 15 @ 60 sec  Total Integration Time: 11hr
	@ Gain 120 & 30 Offset 21 @ -15oC
Calibration	5 x 300 sec & 20 x 60 sec Darks + 10 x  NB & 20x BB Flats & Dark Flats          @ ADU 32,000
Location & Darkness	Castle Farm Observatory, Wookey, Somerset       Bortle 4
Date & Time	23rd 24th 25th & 28th September 2025 @ +20.45h
Weather	Approx. <7oC   RH >=<60%    🌙 <= 38% Waxing Crescent