Apparently it's called the crescent nebula because that's what it looks like through a visual telescope. I think it looks more like a scrotum ¯\_(ツ)_/¯
This is my third time shooting the Crescent Nebula! I had first shot it back in 2017 when I still used a DSLR for astrophotography. I still use the same scope, but eventually upgraded to a monochrome astro cam, and this was my first target using Hydrogen alpha + Oxygen-iii narrowband filters in 2019. Last year I decided to shoot it again, although I combined this data with the data from 2019 since my setup then was identical to how it is now. I did have to heavily crop in on this image due to differing camera rotations, but I ended up with a higher signal to noise ratio overall by combining the data. I also made a starless version of this pic which better shows off the faint nebulosity, including the Soap Bubble Nebula in the bottom left.
Captured over 5 nights in May 2019 (Bortle 7) and 4 nights in May 2022 (Bortle 6)
Places where I host my other images:
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TPO 6" F/4 Imaging Newtonian
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Orion Sirius EQ-G
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ZWO ASI1600MM-Pro
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Skywatcher Quattro Coma Corrector
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ZWO EFW 8x1.25"/31mm
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Astronomik LRGB+CLS Filters- 31mm
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Astrodon 31mm Ha 5nm, Oiii 3nm, Sii 5nm
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Agena 50mm Deluxe Straight-Through Guide Scope
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ZWO ASI-120mc for guiding
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Moonlite Autofocuser
Acquisition: 26 hours 5 minutes (Camera at Unity Gain, -15°C)
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Ha - 61x360" + 88x300"
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Oiii - 54x360" + 87x300"
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Darks- 30
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Flats- 30 per filter
Capture Software:
- Captured using N.I.N.A. and PHD2 for guiding and dithering.
PixInsight Processing:
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BatchPreProcessing
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SubframeSelector
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StarAlignment
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ImageIntegration
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DrizzleIntegration (2x, Var β=1.5)
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DynamicCrop
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DynamicBackgroundExtraction
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EZ Decon
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NoiseXTerminator
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STF applied via HT to bring each image nonlinear
Combining Channels:
really like how the colors turned out on this, especially the slight gold/yellow in the nebula compared to the red in the background
- Pixelmath to make RGB image using ForaxX's HOO palette:
R= Ha
G= ((Oiii*Ha)^~(Oiii*Ha))*Ha + ~((Oiii*Ha)^~(Oiii*Ha))*Oiii
B= Oiii
Nonlinear:
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LRGBCombination with extracted L as luminance, used for chrominance noise reduction
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Shitloads of CurveTransformations to adjust lightness, saturation, contrast, hues, etc. with various masks
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NoiseXTerminator
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More Curves
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EZ star reduction
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NoiseGenerator to add noise into reduced star areas
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Even more curves
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ColorSaturation to better bring out the Oiii regions
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More NoiseX
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Resample to 80%
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Annotation
Great job! Please excuse my ignorance, but what's that thing in the middle that looks like a hole?
it's a cloud of dust in the foreground of the nebula blocking some of the light