The Medusa Nebula (Abell 21)

Type: Old Planetary

Constellation: Gemini

Distance from Earth: 1,500 light-years

About: The Medusa Nebula, a substantial planetary nebula, spans approximately one-third of the diameter of a full moon. Initially identified by George O. Abell during the 1950s, it was cataloged as the 21st item in his list. Its naming as “Medusa” stems from its resemblance to a jellyfish, characterized by intricate, sinuous filaments. Interestingly, the nebula’s spectrum exhibits a relatively subdued emission in O-III compared to the norm, as H-alpha appears roughly twice as intense.

Imaging Project Information:

Imaging Telescope: Celestron EdgeHD 8″ Schmidt-Cassegrain

Imaging Camera: ZWO ASI533MM Pro

Mount: iOptron CEM60

Filters and Frames:
Antlia Blue 1.25″: 30×60″(30′)
Antlia EDGE H-alpha 4.5nm 1.25″: 62×300″(5h 10′)
Antlia EDGE OIII 4.5 nm 1.25″: 65×300″(5h 25′)
Antlia Green 1.25″: 30×60″(30′)
Antlia Red 1.25″: 30×60″(30′)

Accessories: Celestron 0.7X Reducer  · Celestron Off-Axis Guider · MeLE Overclock 4c · Pegasus Astro Powerbox Advance Gen2 · Pegasus Astro Uranus Meteo Sensor · Pegasus Astro USB Control Hub · Primaluce Lab Essato 2″ LP robotic focuser · Primaluce Lab GIOTTO 255 Smart Flat Field Generator · ZWO EFW 8 x 1.25″

Software: Acquisition – Nightime Imaging and Astronomy (N.I.N.A), Preprocessing: Aries Astro Pixel Processor, Postprocessing: Pleiades Astrophoto Pixinsight

Acquisition Period: February 28-29, March 2, 10, 11, 2024

Total Integration: 12h