NGC1365 – Great Barred Spiral Galaxy


Twenty-five 5-minute light frames, calibrated, registered, stacked, and post-processed using PixInsight. I was having a bit of trouble before this shot, my stars had colour fringes caused by the coma corrector. I have started performing my collimation with the coma corrector in place, which seems to have reduced this problem significantly. I think it’s just because the coma corrector isn’t as snug a fit as it should be in the focuser tube.

  • Date taken: 27/11/2014
  • Location: Adelaide, South Australia
  • Camera: Canon 450d w/ IR filter removed, GSO coma corrector
  • ISO800
  • Mount: HEQ5PRO
  • Scope: GSO 8″ f/5 Newtonian
  • Autoguider: Orion Starshoot AG
  • Imaging: BackyardEOS w/ PHD dithering
  • Guiding: PHD2
  • 50 bias frames, 20 dark frames, 50 flat frames.
  • Total integration time: 125 minutes

Pre-Processing details:

  • BatchPreProcessing, calibration only
  • BatchDebayer
  • Star Alignment
  • Image integration (using Winsorized Sigma Clipping)
  • Dynamic Background extraction, twice, first time to remove the majority of the light pollution, then a second run to reduce some of the gradients from nearby light sources.
  • Dynamic Crop to remove some of the dodgy edges, also centering the image on NGC1365
  • Extracted luminance from the RGB for later on

Processing the RGB Image:

  • BackgroundNeutralization
  • ColourCalibration
  • ATrousWaveletTransform to reduce noise
  • HistogramTransformation to reveal the galaxy etc
  • ACDNR to further improve noise
  • ATrousWaveletTransform a few more times with various masks to reduce noise and even out the background
  • Blurred the RGB image with ATrousWaveletTransform by removing all the detail from the first 4 layers!

Processing the luminance image:

  • Much the same as before, ATrousWaveletTransform to reduce noise
  • HistogramTransformation to stretch the image
  • More ATrousWaveletTransform, this time using a mask generated from a cloned image, HistogramTransformation used to auto clip highlights & shadows
  • Same mask, ACDNR.
  • Bit more HistogramTransformation now that there is a lot less noise
  • Pixel math: star_mask+range_mask, masking everything but the stars and galaxy
  • LocalHistogramEqualization to bring out some more detail in the galaxy
  • Tiny bit of bias in ATrousWaveletTransform to sharpen up the galaxy

Putting the images together:

  • LRGBCombination!
  • Saturation increased a tad, 0.350 or so, but otherwise just applied L to RGB
  • CurvesTransformation to tweak the saturation and luminance a tad, and increase contrast

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