Medusa Nebula: Abell 21 (Ashraf AbuSara)

Celestial hemisphere: Northern · Constellation: Gemini (Gem) · Contains: PK205+14.1 · Sh2-274

Medusa Nebula: Abell 21

Sh2-274 / Abell 21, aka the Medusa Nebula, is a planetary nebula located in the constellation Gemini. It is about 1500 light years away, and 4 light years wide. At the center of Abell 21, is a PG 1159 star. These are also known as pre-degenerate stars. Pre-degenerate star is a star with a hydrogen-deficient atmosphere that is in transition between being the central star of a planetary nebula and being a hot white dwarf. These stars are hot, with surface temperatures between 75,000 K and 200,000 K, and are characterized by atmospheres with little hydrogen and absorption lines for helium, carbon and oxygen. WD0726+133 is the central star of the Medusa nebula is marked here in revision B.

I imaged this last night from my backyard as a last minute choice on an unexpected clear night. It was nearly a full moon. Thankfully, with narrowband imaging one can still get acceptable results from emission nebulae. I decided to process this with Foraxx palette utility that utilizes dynamic narrowband combinations. I only gathered just under 5 hours of data, and it was rather windy, so it was difficult to tease out the Oiii outer waves while preserving the central Ha data. This was a fun last minute project despite the rather short integration time. When it comes to backyard winter imaging, beggers can't be choosers.

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B

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Status	Advanced success
Started	...
Astrometry.net job	8959096
PixInsight job	Z1GBWTICXWTQVRUUG3U5E9CQBGS7NVKV
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	07h28m56s.453
RA (top/left)	07h30m05s.113
RA (top/right)	07h28m35s.208
RA (bottom/right)	07h27m48s.630
RA (bottom/left)	07h29m17s.697

Dec (center)	+13°14′23″.42
Dec (top/left)	+13°15′55″.58
Dec (top/right)	+13°30′19″.51
Dec (bottom/right)	+13°12′50″.91
Dec (bottom/left)	+12°58′27″.57

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Medusa Nebula: Abell 21

Medusa Nebula: Abell 21

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Medusa Nebula: Abell 21

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