Hemisphere:  Northern  ·  Constellation: Gemini (Gem)
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Abell 21 • Sh2-274 • Medusa Planetary Nebula, 



    
        

            Douglas J Struble
Abell 21 • Sh2-274 • Medusa Planetary Nebula
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Abell 21 • Sh2-274 • Medusa Planetary Nebula

Getting plate-solving status, please wait...
Abell 21 • Sh2-274 • Medusa Planetary Nebula, 



    
        

            Douglas J Struble
Abell 21 • Sh2-274 • Medusa Planetary Nebula
Powered byPixInsight

Abell 21 • Sh2-274 • Medusa Planetary Nebula

Technical card

Imaging telescopes or lenses: Explore Scientific 152 mm Carbon Fiber  ·  Stellarvue SVX102T-R

Imaging cameras: ZWO ASI1600MM-Cool

Mounts: Astro-Physics Mach 1 GTO  ·  Orion Atlas Pro AZ/EQ-G

Guiding telescopes or lenses: Stellarvue 50mm Guidescope  ·  Orion 80mm Short Tube

Guiding cameras: ASI224MC  ·  Starlight Xpress Lodestar x2

Software: Photoshop CC  ·  PHD2  ·  Sequence Generator Pro  ·  PixInsight

Filters: Astrodon Ha 5nm  ·  Astrodon OIII 3nm  ·  Astronomik Deep-Sky B  ·  Astronomik Deep-Sky G  ·  Astronomik Deep-Sky R

Accessory: QHYCCD PoleMaster  ·  ZWO 8x 1.25" Filter Wheel (EFW)  ·  Hotech 2" SCA Self-Centering Field Flattener  ·  MoonLite CFL 2.5" Large Format Focuser


Dates:Feb. 18, 2019March 2, 2019March 16, 2021April 2, 2021April 3, 2021April 12, 2021

Frames:
Astrodon Ha 5nm: 785x120" (26h 10') (gain: 200.00) -20C bin 1x1
Astrodon OIII 3nm: 577x120" (19h 14') (gain: 200.00) -20C bin 1x1
Astronomik Deep-Sky B: 60x60" (1h) (gain: 0.00) -20C bin 1x1
Astronomik Deep-Sky G: 60x60" (1h) (gain: 0.00) -20C bin 1x1
Astronomik Deep-Sky R: 60x60" (1h) (gain: 0.00) -20C bin 1x1

Integration: 48h 24'

Darks: 50

Flats: 50

Bias: 250

Avg. Moon age: 13.95 days

Avg. Moon phase: 42.16%

Bortle Dark-Sky Scale: 8.00


Basic astrometry details

Astrometry.net job: 4433484

RA center: 7h 28' 54"

DEC center: +13° 17' 2"

Pixel scale: 0.553 arcsec/pixel

Orientation: 224.585 degrees

Field radius: 0.426 degrees


Resolution: 3467x4335

Data source: Backyard

Description

I tried capturing Abell 21 (Sh2-274) in the Spring on 2019. Typically Springs here in Michigan are pretty bad with clear skies and was only able to gather 12.8 hours of integration time between Ha and OIII back then. We had a very unusual March this year with a lot of clear nights and added on data to what a collected before. While I wanted to bring out more detail in the nebula itself, there was a lot of background nebula I wanted to pull out as well and see how far I can sharpen it.

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 OIII.

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Abell 21 • Sh2-274 • Medusa Planetary Nebula, 



    
        

            Douglas J Struble