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.

Places where I host my other images:

Flickr | Instagram

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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-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. and PHD2 for guiding and dithering.

PixInsight Preprocessing:

• BatchPreProcessing

• StarAlignment

• Blink

• 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.

• 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)

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