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The Cygnus loop (radio source W78 or Sharpless 103) is a large expanding cloud of hot dust and gas born of the death explosion of a massive star in the constellation of Cygnus. The nebula is 1,500 light-years away and the supernova that created it occurred 5,000 to 8,000 years ago and would have been bright enough to be seen with the naked eye from Earth.
StarAllignment of the linear Hydrogen-α and Oxygen III data using the Hydrogen-α frame as a reference.
DynamicCrop on both of them using the same process.
Background Noise removal with AutomaticBackgroundExtractor on both frames.
LinearFit on the integrated Hydrogen-α frame to balance the emissions, as the emissions of the Oxygen III are weaker than the Hydrogen-α frame (the nebulosity is stronger in the Hydrogen-α frame).
Noise reduction with MultiscaleLinearTransform. 4 layers with the following settings (R as default):
Layer 1: Threshold 0.500, Amount 0.50, Iterations: 1
Layer 2: Threshold 0.500, Amount 0.50, Iterations: 1
Layer 3: Threshold 0.500, Amount 0.50, Iterations: 1
Layer 4: Threshold 0.500, Amount 0.50, Iterations: 1
The PixelMath formula:
R: HA
G: HA * 0.2 + OIII * 0.8
B: OIII
Optimisations with CurvesTransformation and STF auto-stretch (linked RGB Channels) with the HistogramTransformation.
Further noise reduction using ACDNR with the following settings:
Lightness: (StdDev 1.0, Amount 0.20, Lightness mask enabled, Bright Sides Edge Protection - Threshold 0.015, Overdrive 0.00)
Chrominance: (StdDev 0.1, Amount 1.00, Lightness mask enabled, Bright Sides Edge Protection - Threshold 0.030, Overdrive 0.00)
Further colour and balance optimisations with Camera Raw Filter.
August - September 2019, Bedworth, GMT+0, United Kingdom, Bortle Class 5 ~SGM: 19.57 mag./arc sec2
Camera: ZWO ASI 1600MM-PRO USB 3.0 Mono (Type CMOS)
Sensor Cooling Temperature: -15C
Filters: 1.25" 5nm Astrodon Ha, 1.25" 3nm Astrodon OIII
Imaging Telescope: Takahashi FS-60CB
Correcting Lens: Takahashi Reducer 0.72x (composite focal length at 264mm and focal ratio at f/4.9)
Mount: iOptron CEM25EC
12Bit ADC (FITS)
32 x 180" Ha subs (Gain 139, Offset 21, Binning 1x1)
28 x 300" Ha subs (Gain 139, Offset 21, Binning 1x1)
13 x 600" Ha subs (Gain 139, Offset 21, Binning 1x1)
24 x 180" OIII subs (Gain 139, Offset 21, Binning 1x1)
28 x 300" OIII subs (Gain 139, Offset 21, Binning 1x1)
12 x 600" OIII subs (Gain 139, Offset 21, Binning 1x1)
11hrs 38mins
20 Darks, 20/20 Flats for Ha/OIII
PixInsight 1.8 Core
Photoshop
SharpCap