pics

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