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I've tweaked my processing of my first SHO image and am looking for any suggestions on how to improve my workflow. The steps I took after image selection, calibration, registration and stacking were: * DynamicCrop on individual SHO masters to remove slight registration borders * DynamicBackgroundExtration on each master image * LinearFit using the weakest channel as the reference * MaskedStretch on the individual channels * Extracted Ha and OIII stars using Starnet++ and also removed stars from SII master * Combined the 3 channels using ChannelCombination (SHO) to end up with a starless RGB image * MultiscaleMedianTransform to denoise the new starless RGB image * ArcsinhStretch on the starless RGB image to give it some punch * Created a mask using Rangeselection with some bluring and smoothing to work on just the nebula rather than the background * Applied an SCNR (green) at 35% twice to the nebula * Removed the mask and applied a 3rd SCNR (green) at 35% to just tweak a bit of green from the whole image including the background * Combined the Ha and OIII star masks using PixelMath (R=Ha, G=Ha*0.2+OIII*0.8, B=OIII) to create RGB(ish) stars * Histogram transformation to get my RGB stars to about the level I wanted * Used CurvesTransformation (Hue) on the stars to just tweak the colour of them a bit as there was still a bit of green in the white stars * PixelMath to add starless RGB image to stars image * One final DynamicBackgroundExtraction to remove a slight top to bottom gradient Please feel free to be hyper-critical as I know have a lot more to learn and I won't take offence.  The full size image is  Crab Nebula SHO using a cheap newtonian |
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Your image looks nice and it seems you have your PI workflow in order now. It's similar to mine. I haven't tried the ArcsinhStretch on the RGB stars yet. I'll give that a try. Thanks! I have one other 3 step process that I use to reduce star size I picked up from Shawn Nielson (Visible Dark) on youTube that includes: Multiscale Transform/Star Mask/Morphological Transformation Eddie |
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I have one other 3 step process that I use to reduce star size I picked up from Shawn Nielson (Visible Dark) on youTube that includes: Thank you! I will look into that. I didn't do star reduction on this one as I'm having mixed results and they have ended up looking a bit false with too many artefacts. I've tried using deconvolution carefully on the stars and that was sort of OK. I've also tried using the Star De-emphasizer script, but that left me with too many artefacts at my imaging scale. That's definitely one area that needs a lot of careful handling. |
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For stretching I'm a huge fan of GHS: Generalised Hyperbolic Stretch Version 2.1.0 - AstroBin In case of processing multiple sessions you may give NormalizeScaleGradient Script a try: PixInsight NormalizeScaleGradient Part 1: Introduction - YouTube PixInsight NormalizeScaleGradient Part 2: Setup - YouTube PixInsight NormalizeScaleGradient Part 3: Output and Results - YouTube Clear skies Wolfgang |
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| Do you have your processes ordered and stacked in the right column and saved as a project that you can load when you open PI? It's a wonderful feature. |
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Do you have your processes ordered and stacked in the right column and saved as a project that you can load when you open PI? It's a wonderful feature. I do now. Very handy; thanks. |
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| FWIW: I've decided to use MultiscaleLinearTransform earlier in the process now for noise reduction; i.e. on the individual linear channels after the linear fit. I'm using an inverted mask created using a duplicate of each channel that has had the STF applied using HistogramStretch. I think this is a pretty standard approach and one which leaves me with more detail in the nebula whilst removing most of the pesky noise from the background. |
