This target has always been a goal of mine since starting in this hobby. While the Flying Nebula (aka Sh2-129, all the red stuff), the Squid Nebula (aka OU4, the blue stuff) was only discovered in 2011. It's stupidly faint. Because of this, and my horrible light pollution, I had to get a *ton* of exposure time to bring it out, and ended up getting 110 hours total time on it. This is a combination of images taken through hydrogen-alpha and oxygen-iii filters for the nebulosity, plus RGB filters for true-color stars (the nebulosity is kinda close to true color). I have no clue why the Ha region is called 'the flying bat', but the Oiii structure sure looks like a squid alright.
Captured over a shitload of nights from September to December, 2023. Broadband data from a Bortle 9 zone.
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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-290mc for guiding
* Moonlite Autofocuser
**Acquisition:** 110 hours 15 minutes (Camera at -15°C)
> BB exposures at half unity gain (76/15), Ha at unity gain (139/21)
* Ha - 212x600"
* Oiii - 428
* L - 200x120"
* R - 69x60" 69 71 66
* G - 71x60"
* B - 66x60"
* 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 Preprocessing:**
* BatchPreProcessing
* StarAlignment
* [Blink](https://youtu.be/sJeuWZNWImE?t=40)
* ImageIntegration per channel
* DrizzleIntegration (2x, Var β=1.5)
* Dynamic Crop
* DynamicBackgroundExtraction
> 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:
* Honestly just StarXterminator and EZ soft stretch to bring them nonlinear.
* Duplicated the Oiii before stretching to be used for advanced narrowband combination:
**Oiii advaned narrowband combination:**
> These steps largely follow the ones in Jimmy/[NightPhoton's advanced narrowband combination guide](https://www.nightphotons.com/guides/advanced-narrowband-combination).
* Combine Oiii with Green broadband channel channel (OGG palette)
* BackgroundNeutralization
* ColorCalibration
* StarXterminator to completely remove stars
* PixelMath to subtract green continuum spectrum, leaving just Oiii signal
* HistogramTransformation to stretch nonlinear
* NoiseXterminator + a little concolution
* CurvesTransformation to adjust black point/contrast
* Clone stamp to remove a couple background artifacts
* image saved as 'NB', to be combined later on in nonlinear processing
**RGB Linear:**
> this is really just to have natural star colors
* SpectroPhotometricColorCalibration
* BlurXTerminator
> Really loving the star correction with its new AI v4 update
* HSV Repair
* StarXterminator to make a stars-only image
* ArcsinhStretch + Histogram transformation to bring stars nonlinear
**Nonlinear processing:**
* Combined stretched Ha and Oiii images into a color image using ForaxX's HOO palette:
> R = Ha
> G= ((Oiii\*Ha)^~(Oiii\*Ha))\*Ha + ~((Oiii\*Ha)^(Oiii\*Ha))\*Oiii
> Oiii
* Background Neutralization
* Shitloads of Curve Transformation to adjust lightness, saturation, contrast, hues, etc with various masks
* LocalHistogramEqualization
* Added in NB image from earlier per the advanced narrowband guide
> only difference from the pixelmath in the guide is that I added NB to the green and blue channels (0.6 and 0.9, respectively) instead of red
* HistogramTransformation to adjust the black point
* More curves
* MLT for medium scale noise reduction in the squid
* ColorSaturation to slightly desaturate the red nebulas
* NoiseXterminator
* Even more curves
* 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
> (Jimmy is a processing wizard when it comes to writing up this [independent starless processing stuff](https://www.nightphotons.com/guides/star-addition))
> mtf(.005,
> mtf(.995,Stars)+
> mtf(.995,Starless))
* Guess what more curves
* Another round of NoiseXterminator
* MLT for some small scale chrominance noise reduction
* Few more slight ColorSaturation adjustments
* Resample to 60%
* Annotation
lefty7283
