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

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