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Ursa Astronomical Association
Kopernikuksentie 1
00130 Helsinki

Ursa Astronomical Association

Abell 21 - 19.3.2021 at 21.00 Imatra Observation number 96908

Visibility I / V

Rauno Päivinen, Etelä-Karjalan nova

Abell 21, or jellyfish mist, is a planetary-sized object in the constellation of twins. Although the object is large, it is unfortunately also dull in surface brightness, i.e. a challenging object of observation both visually and pictorially.

Maybe that’s why you don’t see new pictures of this very often.

I took this planetary first imaging set in 2017 and now 4v later a new attempt. Images were taken with C14 and H-alpha as well as OIII filters and composed as HOO color image. In black-and-white sub-images, the faint parts of the fog are better distinguished, which still extend beyond the field of view. Here’s a good subject for owners of a dark scene and a bright and slightly wider picture tube.

First image HOO color version. H-alpha in the red and OIII in the green and blue channels.

Another image of an h-alpha stack

in the third h-alpha stack as a negative, opaque areas stretched out

Fourth OIII stack

The fifth OIII stack is a stretched negative.

More similar observations
Additional information
  • Observation target
    • Deep space object
  • Designation
    • Abell 21
    • Erittäin heikosti näkyvä
  • Brightness in magnitudes
    • 14
  • Field of view
  • 24 arc minutes
  • Darkness
    • Mediocre
  • Seeing
    • Average
  • Nebulae
    • Planetary nebula info

      Planetary nebula is the remnant of a death star. It could be ring-shaped, disc-like or spread out rather irregularly.

      With the exception of some nearest objects planetary nebulae have a small apparent diameter and they need a rather big instrument to be visible.


      Planetary nebula M27 aka The Dumbbell Nebula in Vulpecula. Image Juha Parvio.


      M76 aka The Little Dumbbell Nebula in Perseus. Image Rauno Päivinen.

Technical information

Celestron C14 and Optec 0.5X focal length reducer. Atik 460EX mv CCD camera. Astrogon 5nm h-alpha and 3nm OIII filters

Comments: 2 pcs
Raimo Hakala - 20.3.2021 at 15.58 Report this

Olet saanut tosi hyvät kuvat meduusasumusta. Musta valkoisessa kuvassa erottuu erittäin hyvin sumun rakenteet.

Timo Inkinen - 21.3.2021 at 22.35 Report this

Hieno havaintokuva Meduusa-sumusta, kohde saanut arvoisensa loppukäsittelyn, onnittelut!

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