So I shot the Bubble Nebula in true-color last year, but I decided to shoot it again this past month in false color. It really helps to show the extended nebulosity, and gives me and excuse to compare my image to Hubble’s. This false color image uses the SHO palette, where the sulfur-ii wavelength is mapped to red, hydrogen-alpha to green, and oxygen-iii is blue. I’m really happy with how the colors turned out on this one. There’s also a number of other nebulae and a star cluster in frame. Captured over 14 nights in Jan/Feb 2024 from a bortle 9 zone (I could only get a couple hours max per night on it.
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:
Blur and NoiseXTerminator
Duplicated the images before stretching to be used for separate stars-only processing
Slight stretch using HistogramTransformation
iHDR 2.0 script to stretch each channel the rest of the way.
Stars Only Processing:
PixelMath to combine star images (SHO palette)
SpectroPhotometricColorCalibration (narrowband working mode)
StarXTerminator to make stars only image form each channel
SCNR > invert > SCNR > invert to remove greens and magentas
ArcsinhStretch + HT to stretch nonlinear - to be combined later with starless pic
Nonlinear:
PixelMath to combine stretched Ha, Oiii, and Sii images into color image (SHO palette)
StarXterminator to remove stars
HistogramTransformations to tone back the greens and apply a more aggressive stretch to red and blue channels
Shitloads of Curve Transformations to adjust lightness, hues, contrast, saturation, etc
LRGBCombination with stretched Ha as luminance
DeepSNR
more curves
ColorSaturation to bring up the blues in the bubble
LocalHistogramEqualization
even more curves
MLT for chrominance noise reduction
Pixelmath to add in the stretched stars only image from earlier
This basically re-linearizes the two images, adds them together, and then stretches them back to before
So I shot the Bubble Nebula in true-color last year, but I decided to shoot it again this past month in false color. It really helps to show the extended nebulosity, and gives me and excuse to compare my image to Hubble’s. This false color image uses the SHO palette, where the sulfur-ii wavelength is mapped to red, hydrogen-alpha to green, and oxygen-iii is blue. I’m really happy with how the colors turned out on this one. There’s also a number of other nebulae and a star cluster in frame. Captured over 14 nights in Jan/Feb 2024 from a bortle 9 zone (I could only get a couple hours max per night on it.
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, Sii 5nm
Agena 50mm Deluxe Straight-Through Guide Scope
ZWO ASI-290mc for guiding
Moonlite Autofocuser
Acquisition: 37 hours 36 minutes (Camera at -15°C), Camera at unity gain.
Ha - 95x360"
Oiii - 140x360"
Sii - 141x360"
Darks- 30
Flats- 30 per filter
Capture Software:
PixInsight Preprocessing:
BatchPreProcessing
StarAlignment
Blink
ImageIntegration per channel
DrizzleIntegration (2x, Var β=1.5)
Dynamic Crop
DynamicBackgroundExtraction
Narrowband Linear:
Blur and NoiseXTerminator
Duplicated the images before stretching to be used for separate stars-only processing
Slight stretch using HistogramTransformation
iHDR 2.0 script to stretch each channel the rest of the way.
Stars Only Processing:
PixelMath to combine star images (SHO palette)
SpectroPhotometricColorCalibration (narrowband working mode)
StarXTerminator to make stars only image form each channel
SCNR > invert > SCNR > invert to remove greens and magentas
ArcsinhStretch + HT to stretch nonlinear - to be combined later with starless pic
Nonlinear:
PixelMath to combine stretched Ha, Oiii, and Sii images into color image (SHO palette)
StarXterminator to remove stars
HistogramTransformations to tone back the greens and apply a more aggressive stretch to red and blue channels
Shitloads of Curve Transformations to adjust lightness, hues, contrast, saturation, etc
LRGBCombination with stretched Ha as luminance
DeepSNR
more curves
ColorSaturation to bring up the blues in the bubble
LocalHistogramEqualization
even more curves
MLT for chrominance noise reduction
Pixelmath to add in the stretched stars only image from earlier
A round of NoiseXterminator for good measure
Resample to 60%
Annotation