this post was submitted on 28 Aug 2023
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Astrophotography
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The noise reduction on this is spot on, nice!
Thanks!
VdB 152 is technically just one part at the end of the dark nebula, and there are a number of other cataloged structures in this image. Captured from August 16-25, 2023. Broadband data from a Bortle 3 zone (Deerlick astronomy village), Ha from Bortle 9.
Places where I host my other images:
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TPO 6" F/4 Imaging Newtonian
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Orion Sirius EQ-G
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ZWO ASI1600MM-Pro
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Skywatcher Quattro Coma Corrector
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ZWO EFW 8x1.25"/31mm
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Astronomik LRGB+CLS Filters- 31mm
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Astrodon 31mm Ha 5nm, Oiii 3nm, Sii 5nm
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Agena 50mm Deluxe Straight-Through Guide Scope
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ZWO ASI-290mc for guiding
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Moonlite Autofocuser
Acquisition: 30 hours 15 minutes (Camera at -15°C)
BB exposures at half unity gain (76/15), Ha at unity gain (139/21)
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Ha - 102x600"
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L - 200x120"
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R - 70x120"
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G - 70x120"
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B - 68x120"
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Darks- 30
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Flats- 30 per filter
Capture Software:
- Captured using N.I.N.A. and PHD2 for guiding and dithering.
PixInsight Preprocessing:
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BatchPreProcessing
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StarAlignment
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ImageIntegration per channel per panel
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DrizzleIntegration (2x, Var β=1.5)
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Dynamic Crop
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DynamicBackgroundExtraction
Luminance Linear:
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BlurXterminator
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NoiseXterminator
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ArcsinhStretch + HistogramTransformation to stretch to nonlinear
Ha Linear:
These steps largely follow the ones in NightPhoton's advanced narrowband combination guide.
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Combine Ha with Red channel (HRR palette)
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BackgroundNeutralization
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ColorCalibration
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StarXterminator to completely remove stars
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PixelMath to subtract red continuum spectrum, leaving just Ha signal
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HistogramTransformation to stretch nonlinear
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NoiseXterminator + a little concolution
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CurvesTransformation to adjust black point/contrast
differing from the guide above, the background was a dark gray rather than clipped to black since this is more faint structure addition than bright structure
RGB Linear:
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SpectrophotometricColorCalibration
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Slight SCNR Green
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HSV repair
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ArcsinhStretch + HistogramTransformation to stretch to nonlinear
duplicate stars only was made and stretched to nonlinear using a less aggressive arcsin+HT for star addition later
Nonlinear Processing:
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Various curve adjustments for lightness, contrast, hue, saturation, etc (with varying lum/star masks)
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LRGBCombination using stretched L as luminance
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DeepSNR
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More curves
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PixelMath to add stretched Ha per the advanced narrowband guide above
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BlurXterminator for star reduction
Next few steps kinda follow along with this independent starless processing tutorial for manually combining stars via re-linearization
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StarXterminator
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HistogramTransformation to unstretch (also applied to duplicate stars early image from earlier)
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PixelMath to combine starless + stars only images
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HT to stretch everything back to nonlinear
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MultiscaleLinearTransform for chrominance noise reduction
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LocalHistogramEqualization (2 rounds of this at scales 68 and 384 with lum masks)
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ColorSaturation to selectively saturate reds
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Even more curves
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Resample to 70%
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Annotation
