This image shows the Crescent Nebula diving towards the larger structure that is part of the Gamma Cygni Nebula. The dusty red details throughout the image were captured using a hydrogen-alpha filter, while the star colors were combined in using RGB filters.

Equipment:

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

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

Guidescope: Orion 50mm guidescope

Guiding camera: Orion StarShoot Autoguider

Imaging camera: ZWO ASI1600MM-Cool

Software:

SGP

PHD2

CdC

PixInsight

Acquisition:

Location: Arlington, TX for Ha(Bortle 7), Atoka, OK for RGB(Bortle 3)

Dates: 7/12/17, 7/18/17, 7/19/17, 7/25/17

Gain: 200 Offset: 50 for Ha

Gain: 0 Offset: 10 for RGB

Gain: 75 Offset: 15 for RGB (experimenting)

Camera temp: -15C

Ha: 154x180" Astrodon 5nm

R: 51x180"

G: 50x180"

B: 47x180"

Total integration time: 15hr 6min

64x darks per calibration

30x flats per calibration

200x bias per calibration

Preprocessing:

Batch PreProcessing script to generate calibrated images

StarAlignment to register all frames to the reference

ImageIntegration (Linear Fit rejection)

DrizzleIntegration

DynamicCrop each master

DBE each master

Ha Processing:

Deconvolution

TGV noise reduction (very slightly, via Jon Rista's method)

HistogramTransformation x2

Duplicated the image to create a starless version, using a starmask and several iterations of MMT and MT. Then pushed the faint nebulosity in the starless version using PixelMath expression: "1-(1-$T)*(1-$T)"

Combined the starless version with the image using PixelMath expression "F=0.4; (1-(1-$T)*(1-s)*F)+($T*~F)" followed by the same function but with a value of F=0.2. (s=starless photo).

HistogramTransformation to move black point

LocalHistogramEqualization with inverted starmask

CurvesTransformation for contrast using inverted starmask

DarkStructureEnhance Script

RGB Processing:

LinearFit to Red Channel

ChannelCombination to combine

BackgroundNeutralization

ColorCalibration

SCNR Green

TGV noise reduction (via Jon Rista's method)

HistogramTransformation x2

CurvesTransformation for saturation

ColorSaturation tool to saturate blue stars more

CurvesTransformation using the ColorMask Script to saturate red nebulosity

MorphologicalTransformation for slight star reduction

Created HaRGB image using the script HaRVB-AIP

Script parameters adjusted as follows:

100% HAlpha in R Channel

33% R in HAlpha Channel

Noise It: 3

Transfer functions - Lightness: 0.6 , Saturation: 0.5

ChromaNR used with SmotherdWL: 3 and ProtectedWL: 2

SCNR Green

CurvesTransformation for contrast

Rotated 90deg and Resampled to 50% for web posting