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Sh2-157, commonly known as the Lobster Nebula, is a compact and dynamic emission nebula located in the constellation Cassiopeia, roughly 9,000 light-years from Earth. This region is a site of active star formation, where dense clouds of hydrogen gas are energized by the intense ultraviolet radiation from young, massive stars embedded within.
The nebula’s nickname comes from its distinctive shape: two bright, claw-like lobes of glowing gas extend outward from a central core, giving it the appearance of a cosmic lobster suspended against the star-filled backdrop of the Milky Way. These structures are sculpted by stellar winds and radiation that carve cavities and sharp edges into the surrounding interstellar material.
In narrowband images, the Lobster Nebula shines vividly in hydrogen-alpha, with intricate filaments and dark dust lanes weaving through the brighter emission. Pockets of obscuring dust hint at ongoing stellar birth, while the contrasting textures reveal the turbulent interplay between gravity, radiation, and gas.
Though relatively small compared to vast nebulae like the Rosette or North America Nebula, Sh2-157 stands out for its rich detail and dramatic form, making it a striking and rewarding target for astrophotographers and a fascinating example of star formation in action.
Technical Details
Telescope: Sky-Watcher Esprit 100ED Refractor
Auto Focus: ZWO Electronic Auto Focuser
Astronomy Camera: ZWO ASI183MC Pro
Filter: Optolong UV-IR cut filter; 300 exposures @ 60 seconds each (5 hours)
Filter: Antlia ALP-T Dual Narrowband Ha/Oiii Filter; 720 exposures @ 5 minutes each (60 hours)
Total Integration Time: 65 hours
Auto Guiding: William Optics Uniguide 50mm Guide Scope
Auto Guiding Camera: ZWO ASI120MM Mini Guide Camera
Auto Guiding Software: PHD2
Telescope Mount: Sky- Watcher EQ6-R Pro Equatorial Mount
Telescope Computer: BeeLink GK-55 Mini PC / Windows 10 Pro
Wireless Communication: GL-iNEt Beryl Travel Router
Telescope Control & Image Capture Software: Nighttime Imaging ‘N’ Astronomy (N.I.N.A.)
Image Integration Software: Astro Pixel Process, by Aries Productions
Image Post Processing Software: PixInsight, by Pleiades Astrophoto
Images captured: Palm Springs, CA during August 2025. Dark sky classification = Bright suburban sky (Bortle 6)