Hemisphere:  Northern  ·  Constellation: Gemini (Gem)  ·  Contains:  Sh2-274

Image of the day 06/25/2019

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    Abell 21 (SH2-274) - The Medusa Nebula (Bicolor), 


            Frank Breslawski
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    Abell 21 (SH2-274) - The Medusa Nebula (Bicolor)

    Technical card

    Imaging telescopes or lenses: Lacerta Newton ohne Namen 250/1200

    Imaging cameras: Astrel Instruments AST8300

    Mounts: EQ8

    Guiding cameras: Lacerta MGEN2 with 9x50

    Software: PixInsight 1.8  ·  Zipproth GmbH Straton 2.0

    Filters: Astronomik H-Alpha 6nm CCD  ·  Astronomik OIII 6nm CCD

    Accessory: GPU Pal Gyulai GPU 2" Aplanatic Coma Corrector

    Dates:Feb. 24, 2019Feb. 25, 2019Feb. 26, 2019Feb. 27, 2019

    Astronomik H-Alpha 6nm CCD: 45x900" -20C bin 1x1
    Astronomik OIII 6nm CCD: 36x900" -20C bin 1x1

    Integration: 20.2 hours

    Darks: ~50

    Flats: ~10

    Bias: ~200

    Avg. Moon age: 21.64 days

    Avg. Moon phase: 55.22%

    Bortle Dark-Sky Scale: 4.00

    Astrometry.net job: 3364300

    RA center: 7h 28' 58"

    DEC center: +13° 19' 38"

    Pixel scale: 0.925 arcsec/pixel

    Orientation: 1.542 degrees

    Field radius: 0.424 degrees

    Resolution: 2307x2365

    Locations: Home, Bergisches Land, Germany

    Data source: Backyard


    Also known as Abell 21 and SH2-274, the Medusa Nebula is an old planetary nebula some 1500 light-years away in the constellation Gemini. This PN is shown quite rarely and the outer edge areas are so weak that these can usually not be seen at all on photos...

    Reason enough to try it anyway! :-) An integration time of 11.25 hours only for H-alpha was then sufficient to work out the area of the halo. It looks as if a real wave movement is making its way here. There are also extremely many structures in the core area around the white dwarf star, which causes all this. Hope you like it :-)


    Sky plot

    Sky plot


    Abell 21 (SH2-274) - The Medusa Nebula (Bicolor), 


            Frank Breslawski