The Cygnus Loop - A 41 Hour, 4 Panel HOO Mosaic

            Well, my single most ambitious astrophotography project to date is finally complete and I am VERY pleased with how it came out. It's my first time doing a mosaic as well as my first time shooting over multiple nights as well as my first time getting over 10 hours of exposure time on a single target. Whew. This is gonna be a long write up.

The Cygnus Loop is a supernova remnant - left behind long after a star exploded. It leaves behind a beautiful burst of colors and shapes, including the Eastern and Western Veil Nebulae and Pickering's Triangle. 

This image is a 4-panel HOO bicolor mosaic totaling 41 hours of exposure between all 4 panels.

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Equipment:
- Scope: AstroTech AT65EDQ Quad APO
- Mount: Rowan Belt Modded Orion Sirius EQ-G
- Imaging Camera: ZWO ASI1600mm-Pro
- Guidescope: QHY MiniGuideScope
- Guide Cam: QHY5L-II Mono

Software:
- EQMOD/StellariumScope for mount control
- APT for image capture and platesolving
- PHD2 for guiding
- PixInsight for Processing

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Acquisition:
- Location: Sugar Land, TX
- Gain: 200; Offset: 50; Camera @ -10C
- 248 x 300" Ha - Chroma 5nm
- 244 x 300" OIII - Chroma 3nm
- Nights: 6/5/20, 6/6/20, 6/10/20, 6/11/20, 6/12/20, 6/13/20, 6/15/20, 6/16/20, 6/17/20

Total Integration Time: 41 Hours

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Pre-Processing of each Panel (Apply to each Ha and OIII master panel)
- Integration of all panels
- DynamicCrop to get rid of edges
- DBE on masters

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Initial Processing (done on each Ha and OIII Master Panel)
- Deconvolution via Oke's tutorial
- TGV+MMT via Jon Rista's Tutorial

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Mosaic Process for Each set of 4 masters per Filter
- Run each master through ImageSolver to assign coordinates w/ distortion model generated
- MosaicByCoordinates script to register masters for mosaic
- dnaLinearFit to match background values of registered images
- GradientMergeMosaic to make mosaic for each filter

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Processing of each Mosaic
- HistogramTransformation to Stretch
- HistogramTransformation to bring down background levels
- LocalHistogramEqualization to bring out nebula details w/ rangemask

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Combining the Ha and OIII Mosaics
- DynamicCrop to remove mosaic edges from each filter mosaic
- StarAlignment to align both mosaics
- Combine mosaics into color via PixelMath with the following combination:

- 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))

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Further Processing
- DynamicCrop to remove edges
- invert -> SCNR -> invert to remove magenta tint
- ABE to remove background gradient
- CurvesTransformation on hue to change red hue
- CurvesTransformation on red to bring down red tone
- HistogramTransformation to reduce background further
- CurvesTransformation for contrast
- ColorSaturation w/ rangemask to deepen blues
- CurvesTransformation w/ RangeMask to darken background further
- StarNet++ for StarMask
- Binarize and Convolution on StarMask
- MorphologicalTransformation to reduce stars
- Export to Photoshop to manually take care of seams
- Save and Export
   

Taken on: August 1, 2020

Tags:

Cygnus

veilnebula

astrophotography

astronomy

Nightsky

deepspace

deepsky « less

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