NGC 1579 among Dark Nebula in Perseus
The first completed panel of a large eight-panel project that I have been working on last winter and have resumed this winter. This field is an image of the Dark Nebulas in Perseus, located to the east of the more popular target "California Nebula" as it's dimmer red edges are peaking into the frame on the right hand side. Towards the middle you'll find a small Emissions Nebula: NGC 1579 also known as the Northern Trifid.
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Deep Zoom version of this image was created here as a learning exercise for the larger Patchwork Project being run by /r/astrophotography
Equipment:
* CGEM
* Rokinon 135mm f2 at f2
* asi071mc PRO at -15 C
* Astronomiks L3 UV/IR filter
* AF3 by Deep Sky DadAcquisition:
* 59x120s at unity gainThe resulting image is a combination of the following steps:
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Inspected all subs for bad images with Blink, discarding subs containing clouds
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Calibrated all subs with a master flat and master dark
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Used subframe selector to weight all images based on the following weighting
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(10*(1-(FWHM-FWHMMin)/(FWHMMax-FWHMMin))
+ 30*(1-(Eccentricity-EccentricityMin)/(EccentricityMax-EccentricityMin))
+ 20*(1-(Median-MedianMin)/(MedianMax-MedianMin))
+ 15*(SNRWeight-SNRWeightMin)/(SNRWeightMax-SNRWeightMin)
+ 20*(Stars-StarsMin)/(StarsMax-StarsMin))
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Selected the best sub from subframe and blink to use as a reference frame for aligning and integration
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Cropped the stacking edges of the integrated image
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Dynamic Background Extraction
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Background Neutralization using 4 small preview windows aggregated as a background reference
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Color Calibration |> Solved |> Photometric Color Calibration
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RGBWorking Space to 1,1,1
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Noise Reduction was done using TGV Denoise with a low contrast mask and an autostretched local support and MMT with a very protective luminance mask
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A Synthetic luminance was extracted and stretched using masked stretch to keep the stars relatively small
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ArcSin Stretch was used to stretch the reamining color image
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Image was combined using Channel Combination in CIE L*a*b Mode
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Stars in this image were reduced by using morphological transformation on a countours based mask created with the following steps:
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Extract a luminance, use MLT to remove layer 1 and the residual layer of 6 layers
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Binarize the image using the preview window until only stars, and no structure from the DSO NGC 1579 was left in the mask
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Expand the mask using MTL in Maximize mode: amount 1
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Convolve the image to soften the star mask's edges
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Subtract another copy of the luminance from the resulting star mask, leaving the contoured profiles of the stars from the luminance
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Small round of HDR Multiscale was applied to bring out structure in the nebula
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Small round of Local Histogram Equalization was used to make the dark nebula slightly more prominent
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An curves was applied to increase contrast and the C curve was used to increase saturation with a luminance mask to prevent oversaturation on the stars.
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