Hemisphere:  Northern  ·  Constellation: Gemini (Gem)  ·  Contains:  Eskimo Nebula  ·  NGC 2392
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NGC 2392 - the 'two faced' nebula, 


            Tom Gray
NGC 2392 - the 'two faced' nebula
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NGC 2392 - the 'two faced' nebula

Technical card

Imaging telescopes or lenses: Meade 2080 SCT 8" LX5

Imaging cameras: Meade DSI 3 Pro

Mounts: Meade Fork mount w/wedge Meade

Guiding telescopes or lenses: Meade 8x50mm Finder/Guider

Guiding cameras: Orion Starshoot autoguider

Software: SiliconFields / Ivo Jager Startools v1.7  ·  Stark Labs Nebulosity v3  ·  PHD2 Guiding V 2.6  ·  Meade Envisage V4.10

Filters: Meade RGB-IR Cut 1.25"  ·  Meade LRGB 1.25"

Accessory: Bahtinov Mask  ·  Homemade ST4 autoguider  ·  Finder guider 8x50 Finder Scope

Dates:Feb. 28, 2021

Meade Blue Filter for CCD: 25x30" bin 2x2
Meade Green Filter for CCD: 20x30" bin 2x2
Optolong L-eNhance 1.25": 35x120" bin 1x1
Optolong L-eNhance 1.25": 8x300" bin 1x1
Meade RGB-IR Cut 1.25": 24x120" bin 1x1
Meade Red Filter for CCD: 30x30" bin 2x2

Integration: 3.3 hours

Avg. Moon age: 16.02 days

Avg. Moon phase: 98.22%

Basic astrometry details

Astrometry.net job: 4268468

RA center: 7h 29' 11"

DEC center: +20° 54' 46"

Pixel scale: 0.694 arcsec/pixel

Orientation: 176.749 degrees

Field radius: 0.152 degrees

Resolution: 1223x989

Locations: Home 'observatory' (Bortle 5), Derbyshire, United Kingdom

Data source: Backyard


NGC 2392 is a young planetary nebula in Gemini, made famous as the test target of the renovated HST in Nov 1999 - and what a spectacular image that was. It is also infamous as one of a number of objects that have been renamed, as a result of nicknames that are now considered offensive, politically incorrect or 'two-faced'.

Don't let any of that detract from what an interesting object this is - a double shelled planetary nebula - the outer shell estimated to be about 10,000 years old, and an inner perpendicular shell made of expanding bubbles that may be as young as 1000 years, blowing off the cooling central star.

You can just about make out the two shells in my image and a hint of the ionised LY long filaments of hydrogen in the outer shell (mauve in my image). Alas the core is blown out, and the seeing too unsteady to make much sense of the inner shell.

Despite a reasonable integration there was a lot of noise and gradients in the bright moonlight. I collected L frames first (1 hour), as the moon was rising, followed by RGB (15min each), and then supplemented with more 'luminance' data taken through my tri-narrowband filter - unfortunately the OIII 'leaks' moonlight.

My flat frames were rubbish, a slight change in focus between my LRGB filters which are par focal and the NBF - I need to make a portable light box / electroluminescent panel. Aligned and combined in Nebulosity, and processed in Startools. Colour is dreadful, mainly due to a strong red cast and excessive noise, so I have included the NBF luminance frames for comparison (Rev B).

Of course, this would all benefit from a steady, moonless night... remember those!



  • NGC 2392 - the 'two faced' nebula, 


            Tom Gray
  • NGC 2392 - the 'two faced' nebula, 


            Tom Gray
  • Final
    NGC 2392 - the 'two faced' nebula, 


            Tom Gray


Description: 'Luminance' data collected through my tri- narrow(ish) band filter. This is designed for use with OSCs but is the only narrowband filter that I have - the Ha at 12nm copes well with moonlight, but the OIII is 'leaky' and tends to a lot of noise.

Uploaded: ...


Description: Mixing red with data from NBF helped to bring out the H emissions, and I think has made a subtle difference and improved the overall colour.

Uploaded: ...

Sky plot

Sky plot


NGC 2392 - the 'two faced' nebula, 


            Tom Gray