M76 - The Little Dumbbell Nebula [OC] - eviltoast
  • lefty7283@lemmy.worldOPEnglish
    1·
    9 months ago

    The Little Dumbbell Nebula gets its name because it kinda looks like a tinier version of the Dumbbell Nebla M27 (yes, a different palette was used for this pic). It’s really tiny compared to the uncropped FOV. I’m a lot happier with this attempt at it, compared to my 2019 pic of M76 with the same equipment. I know It’s a bit out of season rn but I needed something to shoot at the start of the night. The nebulosity itself is false color, but the stars are true color RGB. Captured over 10 nights in Feb/Mar 2024 from a bortle 9 zone (I could only get a couple hours max per night on it.

    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-290mc for guiding

    • Moonlite Autofocuser

    Acquisition: 21 hours 6 minutes (Camera at -15°C), NB exposures at unity gain and BB at half unity

    • Ha - 99x360"

    • Oiii - 83x360"

    • R - 101x60"

    • G - 100x60"

    • B - 99x60"

    • 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:

    • Blur and NoiseXTerminator

    • StarXterminator to completely remove stars (to be later replaced by the RGB ones)

    • ArcsinhStretch to slightly stretch nonlinear

    • iHDR 2.0 script to stretch each channel the rest of the way.

    This is a great new pixinsight script from Sketch on the discord. here’s the link to the repo if you want to add it to your own PI install.

    RGB Linear:

    • ChannelCombination to combine monochrome R G and B frame into color image

    • SpectroPhotometricColorCalibration

    • BlurXTerminator for star sharpening

    • HSV Repair

    • StarXterminator to generate a stars-only image

    • ArcsinhStretch + HT to stretch nonlinear (to be combined with starless narrowband image later)

    Nonlinear:

    • PixelMath to combine stretched Ha and Oiii images into color image (/u/dreamsplease’s palette)

    R = iif(Ha > .15, Ha, (Ha*.8)+(Oiii*.2))

    G = iif(Ha > 0.5, 1-(1-Oiii)*(1-(Ha-0.5)), Oiii *(Ha+0.5))

    B = iif(Oiii > .1, Oiii, (Ha*.3)+(Oiii*.2))

    • NoiseX again

    • Shitloads of Curve Transformations to adjust lightness, hues, contrast, saturation, etc

    • LocalHistogramEqualization

    • UnsharpMask

    • More curves

    • ColorSaturation to slightly desaturate the purples

    • even more curves

    • Pixelmath to add in the stretched RGB stars only image from earlier

    This basically re-linearizes the two images, adds them together, and then stretches them back to before

    (again, credit to Jimmy independent starless processing stuff)

    mtf(.005,

    mtf(.995,Stars)+

    mtf(.995,Starless))

    • Couple final curves

    • DynamicCrop waaaay in on the nebula

    • Annotation