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M17 - The Omega Nebula [OC] (live.staticflickr.com)
submitted 10 months ago by lefty7283 to c/pics
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[–] lefty7283 4 points 10 months ago* (last edited 10 months ago) (1 children)

M17 is also known as The Swan Nebula (the bright core is swan shaped, esp when viewed visually through a telescope). Also pictured it the M18 star cluster off to the right.

I originally shot this back in 2019 and decided to reprocess it since we have fun new tools and techniques (and I kinda know what I'm doing now with narrowband processing). I decided to keep the palettes similar overall, but with a less agressive stretch and more 'natural' look to the nebula. The noise reduction is a lot better when comparing the images at 1:1 (long gone are the days of TGV/MMT noise reduction!). Captured over 2 nights at the in May, 2019 from a Bortle 7 zone.

Places where I host my other images:

Flickr | Instagram

Equipment:

  • TPO 6" F/4 Imaging Newtonian

  • Orion Sirius EQ-G

  • ZWO ASI1600MM-Pro

  • Skywatcher Quattro Coma Corrector

  • ZWO EFW 8x1.25"/31mm

  • Astronomik LRGB+CLS Filters- 31mm

  • Astrodon 31mm Ha 5nm, Oiii 3nm

  • Agena 50mm Deluxe Straight-Through Guide Scope

  • ZWO ASI-120MC for guiding

  • Moonlite Autofocuser

Acquisition: 8 hours 10 minutes (Camera at Unity Gain, -15°C)

  • Ha- 42x300"

  • Oiii- 56x300”

  • Darks- 30

  • Flats- 30 per filter

Capture Software:

  • EQMod mount control. Captured using N.I.N.A. and PHD2 for guiding and dithering.

PixInsight Processing:

  • BatchPreProcessing

  • Blink

  • ImageIntegration

  • DrizzleIntegration (2X, VarK 1.5)

  • DynamicCrop

  • DynamicBackgroundExtraction

duplicated each image and removed stars via StarXterminator. Ran DBE with a shitload of points to generate background model. model subtracted from original pic using the following PixelMath (math courtesy of /u/jimmythechicken1)

$T * med(model) / model

Narrowband Linear:

  • BlurXTerminator

  • NoiseXTerminator

  • STF Applied via HT to stretch nonlinear

Nonlinear:

  • PixelMath to combine monochrone Ha and Oiii channels into color image (using ForaxX's bicolor palette):

R = Ha

G= ((Oiii*Ha)^~(Oiii*Ha))*Ha + ~((Oiii*Ha)^~(Oiii*Ha))*Oiii

B = Oiii

  • SCNR Green

  • LRGBCombination with stretched Ha as luminance

  • Shitloads of curve transformations to adjust lightness, contrast, hues, saturation, etc

  • LocalHistoGramEqualization 2x - one at scale 16 for fine details and one at 512 for large structures

  • More curves

  • DarkStructureEnhance

  • MLT for small scale chrominance noise reduction

  • NoiseXTerminator

  • Even more curves, some masked to just the core of the nebula

  • Resample to 60%

  • Annotation

[–] [email protected] 3 points 10 months ago

Thank you so much for writing all this out. I may not need this information right now (no money for gear) but this is still so intesting. I'll come back to this when I've got the money to spare.