In this rendition of The Lagoon Nebula, I blended natural color stars into the false-color image of the nebula. The warmer tones represent where Sulfur and Hydrogen lie in the nebula, while the blues represent the Oxygen emissions.

Equipment:

OTA: William Optics GT81 w/0.8x reducer (382mm fl at f/4.7)

74mm aperture stop-down ring (brings scope to f/5.2)

Mount: Orion Sirius EQ-G (HEQ-5)

Guidescope: Orion 50mm guidescope

Guiding camera: Orion StarShoot Autoguider

Imaging camera: ZWO ASI1600MM-Cool

Accessories:

DeepSkyDad Autofocuser AF1

QHYCCD PoleMaster

Software:

SGP

PHD2

CdC

PixInsight

Acquisition:

Location:

Flower Mound, TX for Ha(Bortle 7) - 2018 data

Atoka, OK for RGB(Bortle 3) - 2018 data

Ft. Griffin State Historic Site, TX for OIII and SII(Bortle 2) - 2020 data

Dates: 6/11/18, 7/31/18, 8/1/18, 6/24/20

Gain: 200 Offset: 50 for Ha

Gain: 76 Offset: 15 for RGB

Camera temp: -10C

SII: 25x300" Astrodon 3nm

Ha: 74x300" Astrodon 5nm

OIII: 26x300" Astrodon 3nm

R: 33x180"

G: 27x180"

B: 30x180"

Total integration time: 14hr 55min

64x darks per calibration (master from library)

30x flats per calibration

200x bias per calibration (master from library)

Preprocessing:

Batch PreProcessing script to generate calibrated images

StarAlignment

ImageIntegration

DynamicCrop

Luminance Processing:

Duplicated the master Ha to use as the luminance

Deconvolution

ArcsinhStretch and HistogramTransformation to bring to non-linear

HDRMT on the core area

Created a duplicate starless version using StarNet++

Combined the starless version with the image using PixelMath expression "F=0.4; (1-(1-$T)*(1-s)*F)+($T*~F)". (s=starless photo)

HistogramTransformation

MultiscaleLinearTransform for sharpening

CurvesTransformation

MorphologicalTransformation using a star mask to completely remove the stars

Preparing separate Sii, Ha, and Oiii linear masters for tonemapping (applied to each master individually):

TGV noise reduction (via Jon Rista's method)

ArcsinhStretch and HistogramTransformation to bring to non-linear

HDRMT on the core area (Ha and OIII only)

Removed stars via StarNet++

Preparing RGB image:

ChannelCombination to create the color image

BackgroundNeutralization

ColorCalibration

SCNR Green

ArcsinhStretch and HistogramTransformation to bring to non-linear

SCNR Green

CurvesTransformation for saturation

SCNR Green (I'm really making sure no stars are green since that is all I'm using this for)

StarNet++ to remove stars and create an RGB star mask

Combined prepared Sii, Ha, and Oiii masters with ChannelCombination:

R: Sii

G: Ha

B: Oiii

Tonemap Processing:

HistogramTransformations to balance colors

CurvesTransformations using ColorMasks

Invert>SCNR Green>Invert to remove magenta in core area

CurvesTransformations for saturation adjustments

Combined Tonemap with Luminance using LRGBCombination

Added in RGB stars using the RGB star mask and PixelMath to add the RGB star-only image to the tonemap

MorphologicalTransformation to slightly reduce star sizes

CurvesTransformation to saturate stars

UnsharpMask to slightly sharpen stars

A few cosmetic adjustments to fix introduced RGB artifacts

Resampled to 80% for web posting