Abell 21 – Sh2-24 (Medusa Nebula)

In 2011, I captured several images of the Abell 21 the Medusa Nebula from my own backyard observatory. To enhance the depth and detail of the final image, I later supplemented my data with additional Hα and [O III] exposures obtained remotely from New Mexico, using the LB0002 telescope operated by LightBuckets in Rodeo.

The final result reveals the intricate structure of Abell 21, a large and faint planetary nebula located in the constellation Gemini. Often called the Medusa Nebula because of its tangled, filamentary appearance, this ancient remnant of a dying star exhibits a beautiful interplay of ionized gases — the red hues of hydrogen contrasting with the teal tones of doubly ionized oxygen.

The data calibration and registration were carried out in DeepSkyStacker, while the final image processing and color composition were completed in PixInsight.

The images were taken with the following equipment:

• Location: Krefeld, Germany – Rodeo, New Mexico
• Telescope: Orion 10″ Newton – ASA 8″ Astrograph
• Focal length [mm]: 1200 – 720
• Focal ratio: 4.8 – 3.6
• Mount: Skywatcher NEQ6, ASA DDM 85
• Camera: Canon 500 Da, Apogee Alta U8300
• Filter: OSC – Hα:[OIII]
• Exposure time [min]: 380 – 64:80
• Resolution: 2.15″/px