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:

Instagram | Flickr

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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-120mc for guiding

• Moonlite Autofocuser

Acquisition: 26 hours 5 minutes (Camera at Unity Gain, -15°C)

• Ha - 61x360" + 88x300"

• Oiii - 54x360" + 87x300"

• Darks- 30

• Flats- 30 per filter

Capture Software:

• Captured using N.I.N.A. and PHD2 for guiding and dithering.

PixInsight Processing:

• BatchPreProcessing

• SubframeSelector

• StarAlignment

• Blink

• ImageIntegration

• DrizzleIntegration (2x, Var β=1.5)

• DynamicCrop

• DynamicBackgroundExtraction

• EZ Decon

• NoiseXTerminator

• 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:

• LRGBCombination with extracted L as luminance, used for chrominance noise reduction

• Shitloads of CurveTransformations to adjust lightness, saturation, contrast, hues, etc. with various masks

• NoiseXTerminator

• More Curves

• EZ star reduction

• NoiseGenerator to add noise into reduced star areas

• Even more curves

• ColorSaturation to better bring out the Oiii regions

• More NoiseX

• Resample to 80%

• Annotation