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Abell 21 - Medusa Planetary Nebula, 


            Douglas J Struble
Abell 21 - Medusa Planetary Nebula

Abell 21 - Medusa Planetary Nebula

Technical card

Resolution: 3139x2510

Dates:Feb. 18, 2019March 2, 2019

Astrodon Ha 5nm: 193x120" (gain: 200.00) -20C bin 1x1
Astrodon OIII 3nm: 192x120" (gain: 200.00) -20C bin 1x1

Integration: 12.8 hours

Darks: ~50

Flats: ~50

Bias: ~250

Avg. Moon age: 19.62 days

Avg. Moon phase: 56.38%

Bortle Dark-Sky Scale: 6.00 job: 2584033

RA center: 112.230 degrees

DEC center: 13.302 degrees

Pixel scale: 0.649 arcsec/pixel

Orientation: 135.340 degrees

Field radius: 0.362 degrees

Locations: Backyard Red Zone Observatory, Taylor, MI, Michigan, United States

Data source: Backyard


Finally finished up a new object. Good old winter blues here in Michigan. What you are seeing in the surrounding area is actually the texture of the gas, not mottling. It could of used more integration time to bring that out more, but I did the best I could bringing that out this time of year.

Although Abell 21, or Sh2-274, has a large apparent diameter of 10 arcminutes, its surface brightness is so low, with features ranging from magnitude 16-25, that it was not discovered until 1955. It is a planetary nebula lying at a distance of 1,500 light-years in the constellation Gemini, which gives it an estimated diameter of 4 light-years. The parent star, now a white dwarf, is thought to be the deep blue star near the center of the crescent. The braided filaments of the shell the star shed during its red giant phase, resemble the serpents that comprise the hair of the mythical character Medusa, giving the nebula its popular name, the Medusa Nebula. The braided shell cradles a sphere of gas glowing a soft blue, largely due to emissions by oxygen III.



Douglas J Struble
License: None (All rights reserved)

Sky plot

Sky plot


Abell 21 - Medusa Planetary Nebula, 


            Douglas J Struble