This is my longest project to date, with 84 hours of long exposure time over 2 seasons going into this photo. Sh2-224 is an extremely faint nebula, and [and this is what a single 10 minute long exposure](https://i.imgur.com/gpKT2dx.png) (through a Ha narrowband filter) of it looks like. I ended up getting ~83 hours of narrowband exposures like this, plus about an hour of RGB images for the stars. Because it's so faint, if the moon was up at all I did not shoot it, which cut the number of clear nights I could reasonably image it in half. The nebula itself is false color (although the HOO palette I used is fairly close to natural color), the stars were taken with RGB filters and are true color, and I finally managed to learn how to do some [starless processing techniques](https://www.nightphotons.com/guides/star-addition) for combining the stars+nebula
Captured over 27 nights between February 2021 and April 2022, from my Bortle 6 driveway
**Places where I host my other images:**
[Instagram](https://www.instagram.com/leftysastrophotography/) | [Flickr](https://www.flickr.com/people/leftysastrophotography/)
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**[Equipment:](https://i.imgur.com/ejpKkwU.jpg)**
* 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:** 83 hours 52 minutes (Camera at Unity Gain, -20°C)
* Ha - 266x600"
* Oiii - 231x600"
* Red- 14x90"
* Green- 14x90"
* Blue- 14x90"
* Darks- 30
* Flats- 30 per filter
**Capture Software:**
* Captured using [N.I.N.A.](https://nighttime-imaging.eu) and PHD2 for guiding and dithering.
**[PixInsight Processing](https://i.imgur.com/vxer28Q.png):**
* BatchPreProcessing
* SubframeSelector
* StarAlignment
* [Blink](https://youtu.be/sJeuWZNWImE?t=40)
* ImageIntegration
* DrizzleIntegration (2x, Var β=1.5)
**Narrowband processing:**
* DynamicCrop
* DynamicBackgroundExtractions
* NoiseXTerminator
* StarXterminator to completely remove stars for starless processing
> to be later replaced by RGB stars. doing this allows the nebula to be stretched without worrying about blowing out stars
* HistogramTransformations to stretch nonlinear
**RGB Linear Processing:**
* DynamicCrop
* DynamicBackgroundExtractions
* ChannelCombination to combine monochrome R, G, and B frames into color image
* PhotometricColorCalibration
* Slight SCNR Green
* HSV Repair
> super useful for putting color back into blown out star cores
* StarXterminator to generate stars only image
> basically just getting rid of the background
* ArcsinhStretch + Histogram transformation to stretch nonlinear
**Combining Channels:**
* ChannelCombination to combine stretched Ha and Oiii images into color image
> Ha mapped to red channel, Oiii to Green and Blue
* HistogramTransformation to [re-linearize](https://www.nightphotons.com/guides/star-addition) HOO and RGB stars images
* PixelMath to add RGB stars only image to starless HOO image
> HOO + Stars the math was simple
* HistogramTransformation to bring HOO+Stars pic back to nonlinear state
**Nonlinear:**
* Shitloads of CurveTransformations to adjust lightness, saturation, contrast, hues, etc. with various masks
* ColorSaturation to selective saturate/desaturate specific hues
* More curves
* Slight SCNR Green
* NoiseXterminator
* LRGBCombination with extracted L as luminance, used for chrominance noise reduction
* even more curves
* color saturation again
* SCNR to remove some green star color
* EZ star reduction
* NoiseGenerator to add noise into reduced star areas
* LocalHistogramEqualization
* guess what baby more [curves!](https://www.youtube.com/watch?v=S1OgCAvOTqA)
* Extract L --> LRGBCombination again with mask for larger scale background chrominance noise reduction
* Resample to 70%
* Annotation
lefty7283
