Mask Nebula

Mask Nebula

Bipolar Planetary Nebula in Circinus

Constellation: Circinus
Ra: 15hr 09m 25s
Dec: -55d 33m 04s
Distance: 6500 light years
Image Size: 30' x 30'
North: Up and Left; East is Left and Down



The Mask nebula is a bipolar planetary nebula (PN G321.6+02.2) about 6500 light years distant in the southern constellation of Circinus.  It is about 8 arcminutes in length, including the bright core that looks like a ski mask, and the extensions.  According to Corradi et al. (“A New, Evolved Bipolar Planetary Nebula”, Astron. Astrophys., v224, 276-280, 1997), it is an evolved planetary nebula with a kinematic age of >12,000 years, very large in size at about 13 light years across, and has a very hot, yet unobserved central star that is hotter than 130,000K.  I used a 5 nm hydrogen-alpha narrowband filter to pick the emissions of both H-a and Nitrogen (NII), since Corradi et al. mentioned that this PN emits much more NII than H-a. The oxygen (OIII) contributes to the brighter regions near the “waist” or constriction of the nebula.


Published in Astronomy, August 2016, p. 71

Exposure: 13.75hrs Total; 7.5hr H-a, 4.5hr OIII, 1.75 hrs RGB
Telescope: PlaneWave CDK20 0.5m f/6.8
Mount: PlaneWave Ascension A200h
Oag: Astrodon MonsterMOAG
Acquisition: ACP8-Expert
Calibration: CCDStack2.0
Observatory Site:, Siding Spring, NSW, Australia
Camera: SBIG STX16803
Filters: Astrodon 5nm H-a, 3nm OIII, Gen 2 RGB
Guider: SBIG ST-i
Camera Operation: MaximDL5.23
Processing: Photoshop cc 2015
Image Date: 04/12/2016 - 04/18/2016


  1. Josep Drudis

    Great image!! It is (by far) the best image of this object that I have found in the web!

    • Sakib

      I definitely agree, this is a marvellous result on a unique planetary nebula and this is the first ever amateur image! Also some extra information, it was originally discovered in 1974 by Pavla Marsalkova as an emission nebula and catalogued as MRSL 252 but only later found to be a PN in 1997.


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