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Astrophotography @lemmy.world lefty7283 @lemmy.world

The Crescent Nebula

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

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

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

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