NGC 6888 – The Crescent Nebula in Cygnus – Dual Narrowband – 24th September 2018 (Ha) and 30th August 2019 (Oiii)

NGC 6888 - The Crescent Nebula in Cygnus - Dual Narrowband

NGC 6888 – The Crescent Nebula in Cygnus – Dual Narrowband

Final summer image, as Autumn officially starts tomorrow!  

This is NGC 6888, the Crescent Nebula in Cygnus.  Floating in the middle of the huge lake of nebulosity that is Cygnus the Swan, is this the result of the Solar Wind from a massive star colliding with the slower solar wind that was ejected for the same star when it became a reg giant about 300,000 years ago.  

This image was taken over the course of more or less a whole year.  The Hydrogen Alpha (red) bit was captured late last summer, and is 3hrs 10min of 5-minute sub frames, with the 4hrs 30min of 5-min OIII (Blue/Green) data being captured last night (30th/31st August).   I used SGP’s plate-solving abilities to identify the position and framing of last year’s capture and pump it into yesterday’s sequence, thus ending up with a very close match to make combining the data fairly straightforward. 

The majority of the image is made up of the Ha image – with most of the nebula emitting in that band, and showing up as red.  Less bright, but still quite obvious is the Oiii shell around the main nebula.  This appears Blue/Green in colour on this dual-narrowband image, which is reasonably close to the real colour it would be in RGB.

All-in-all this was quite a challenge to process.  Getting the colour balance right is much easier when you have a nice black neutral background, but this has pretty much complete coverage with red nebulosity, so there’s no real background black space to speak of.  

Capture and Processing Information

  • Object  – The Crescent Nebula (NGC 6888)
  • Constellation – Cygnus
  • Camera – Atik 314L Mono
  • Exposure OIII – 4 Hours 30 min of 5 min subs
  • Exposure Ha – 3 Hours 10min of 5 min subs
  • Filters – Astronomik 12nm Ha, Baader 7nm OIII
  • Telescope – Altair 102ED f/7 Refractor
  • Mount  – Skywatcher HEQ5 with Rowan Belt Mod
  • Guidescope – Off-axis
  • Guidecam – SX Lodestar
  • Guide Software – PHD2
  • Auto-Focuser – Home-Made MyFocuserPro2 Autofocuser
  • Capture Software  – Sequence Generator Pro
  • Stacking, Colour Combination, and Initial Processing – MaximDL
  • Post-Processing – Photoshop CC and Lightroom CC.

I think this is it for August now…!  See you in the Autumn 😉

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