this post was submitted on 07 Sep 2024
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NGC 4490 is a galaxy colliding with the smaller NGC 4485 galaxy, and both are about 25 million light years away. This image was taken with a monochrome camera through filters for luminance (all visible light), red, green, blue, and Hydrogen-alpha (656nm), which were combined into a color image. The Hydrogen-alpha was combined with red (described below) to make the HaLRGB image. The pink Ha regions are star forming nebulae within the galaxies. This got cropped out of the final pic, but I ended getting some gorgeous diffraction spikes on this star near the edge of the full FOV
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-120MC for guiding
Moonlite Autofocuser
Acquisition: 27 hours 37 minutes (Camera at half Unity Gain, -15°C)
Ha - 128x360"
Lum - 464x60"
Red - 152x60"
Green - 150x60"
Blue - 123x60"
Flats- 30 per filter
24 JimmyFlats per broadband filter
Capture Software:
PixInsight Processing:
BatchPreProcessing (with premade JimmyFlats)
StarAlignment
Blink
ImageIntegration
DrizzleIntegration (2x, Var β=1.5)
DynamicCrop
DynamicBackgroundExtraction
Luminance:
BlurXTerminator
ArcsinhStretch + histogramtransformation to bring nonlinear
RGB:
ChannelCombinaiton to combine monochrome R, G, B stacks into color image
SpectroPhotometricColorCalibration
BlurXTerminator (correct only mode)
HSV Repair
making clean Ha
Nonlinear
ArcsinhStretch + histogramtransformation to bring HaRGB image nonlinear
MLT for large scale chrominance noise reduction
shitloads of curve transformations to adjust lightness, contrast, saturation, etc (with various luminance and star masks)
slight SCNR to remove some greens
LRGBCombination with stretched Luminance
DeepSNR
more curves
ColorSaturation to slightly desaturate the Ha regions (they were very pink compared to the rest of the galaxy
slight noisexterminator
LocalHistogramEqualization
even more curves
Resample to 75%
DynamicCrop onto just the galaxy
annotation
Great pic and thanks for sharing your process.