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Wolf Rayet 134, 





    
        

            Jonathan W MacCollum
Wolf Rayet 134

Wolf Rayet 134

Technical card

Resolution: 5496x3672

Frames:
Astrodon 1.25" 5nm Ha: 101x240" -15C
Astrodon LRGB Tru-Balance I-Series Gen B: 20x60"
Astrodon LRGB Tru-Balance I-Series Gen G: 21x60"
Astrodon O3 1.25" 3nm: 103x240" -15C
Astrodon LRGB Tru-Balance I-Series Gen R: 20x60"

Integration: 14.6 hours

Bortle Dark-Sky Scale: 4.00

Astrometry.net job: 2936001

RA center: 20h 10' 4"

DEC center: +36° 11' 38"

Pixel scale: 0.498 arcsec/pixel

Orientation: 359.148 degrees

Field radius: 0.457

Data source: Backyard

Description

When imaging the [region in Cygnus around the Tulip Nebula](https://www.astrobin.com/422359/D/?nc=user) earlier this summer with my
135mm lens I came across this Blue Streak of Oiii data. I uploaded it hoping someone might comment on what it
was, when suddenly it seemed quite a few people on astrobin were also imaging it... turned out to be the
Wolf-Rayet 134 nebula. Inspired by so many on astrobin and including Chuck's [awesome video](https://youtu.be/Tbn5v13H5ko)
of him shooting this target, I too had to give it a go and suggested it as an option in the upcoming /r/astrophotgraphy OOTM.
Luckly /u/NGC6960 (the winner of last month's OOTM on /r/astrophotograph) ended up picking it for this month! So here is my attempt.
It's the first narrowband image that I have taken at this image scale (non wide-field) so I spent extra time for good measure.
Please let me know what you think of it and if there are specific areas I should look out for to improve in the future!

Equipment:
* 8in f4.9 Newtonian Reflector w/ Sesto Senso Auto Focuser
* Skywatcher Quattro Coma Corrector
* ZWO EFW
* Astrodon LRGB Filters + 3nm Oiii and 5nm Ha
* ZWO ASI 183mm Pro - Cooled to -15.0C
* Celestron CGEM Mount
* Dew Strips around the Primary mirror and Focuser draw tube

Integration/Acquisition Time per Channel:
* R: 20 / 29 x 60s (.3 hrs)
* G: 21 / 30 x 60s (.3 hrs)
* B: 20 / 29 x 60s (.3 hrs)
* Ha: 101/127 x 240s (6.7hrs)
* O3: 103/131 x 240s (6.9hrs)

Total acquisition time: 18 hours 40 minutes
Total rejected frames: 04 hours 03 minutes (removed mostly bloaded and elongated stars from poor guiding)
Total integration time: 14 hours 37 minutes
Data Taken across 5 nights: Sep 1st-Sep 7th
Guiding averaged ~0.9"/px RMS across all nights; Image Scale: 0.5"/px

Flats: 20/filter Calibrated Dark Flats;
Darks: 60/120s @ -15.0C
Bias: None

A superluminance was created by
* Integrating all images with
* Linear Fit Clipping
* Sigma High=9.0
* Sigma Low=9.0
* Drizzle Integration with
* Scale: 1x
* Drop shrink: 0.7
* Kernel Function: Var k=1.5

Luminance Processing (with Super Luminance):
* Crop edges
* No DBE: integrated data felt free of gradients so I skipped this entirely: From a Bortle 4 pointing straight at zenith under little-to-no moon still seemed odd.
* Deconvolution
* Using a dynamic PSF created with 60 stars from around the whole image
* Iterations: 60
* No Deringing
* 5 Layer Gaussian Wavelet Regularization with noise thresholds (12,10,8,5,3) and reduction (0.8,0.8,0.6,0.6,0.3)
* Filled in the ringing left behind with PixelMath ``L_Orig`` and a star mask created by ``L_Orig |> Histogram Stretched |> Starnet in StarMask mode |> MT Maximize |> Convolve``
* One round of gentle noise reduction using TGVDenoise using
* STF for Local Support
* Low Contrast mask
* Stretched a second copy using the Histogram Transformation with STF after shifting the white point to a desirable place
* Created previews around 4 background regions to make a background reference for Masked Stretch
* Masked Stretch
* 1000 iterations
* Used the median of the STF copy's background reference as target
* Created a preview aggregator from the same background references on the target image for stretching
* Histogram to bring the black point in without clipping
* Repeat Masked Stretch a second time
* Blend the Histogram Stretched copy (33%) with the Masked Stretch copy (66%) using PixelMath
* Final luminance smoothing using ACDNR
* StDev 0.8
* Amount: 0.23
* Iterations: 5
* With Luminance Mask enabled
* Remaining: Defaults

Narrowband Processing:
* Stacked each Ha and Oiii images separately using Linear Fit
* Cropped edges using the same Dynamic Crop process from Luminance
* Noise Reduction:
* Small scale TGV
* Stretched with Histogram Transformation
* Additional ACDNR noise reduction on Oiii

RGB data was taken purely to for it's star color
Each color channel was stacked by
* Integrating all images with
* Linear Fit Clipping
* Default rejection settings
* Drizzle Integration with
* Scale: 1x
* Drop Shrink: 0.9
* Kernel Function Var k=1.5
* Crop edges
* Fairly aggressive TGV and MMT Noise Reduction
* Repair blown out star color with the HSV Repair Separation script and Channel Combination
* Stretch with ArcsinhStretch and Histogram Transformation
* Final round of ACDNR Noise Reduction

Combined and Final Touches:
* The Ha and Oiii narrowband data was combined using the following formula:
* Red = Ha
* Blue = Oiii
* Green= ``iif( Ha > .50, 1-(1-Oiii)*(1.5-Ha), Oiii*(Ha+0.5) )``
* LRGB Combination to apply the processed Luminance data with this Narrowband data color image
* Star color was replaced using LRGB Combination of the RGB Stars data and a Star Mask created from the luminance of the previous results
* Oiii enhancements on the final color image:
* Oiii mask = ``((Oiii|>starnet) - (Ha|>starnet) - starmask)|>convolution 1.5``
* Local Histogram Equalization and slight Color Saturation boost
* Ha enhancements on the final color image:
* Ha mask = ``((Ha|>starnet) - (Oiii|>starnet) - starmask)|>convolution 1.5``
* Local Histogram Equalization and slight Color Saturation boost
* Final gentle touch of noise reduction using ACDNR

A starless version was created with Starnet++ (before combination and then recombined the same as above) with residual diffraction spikes and glow cleaned up using Affinity Photo's Inpaint brush.

Comments

Author

eigenVector
Jonathan W MacCollum
License: Attribution-NoDerivs Creative Commons
1943
Like

Revisions

  • Wolf Rayet 134, 





    
        

            Jonathan W MacCollum
    Original
  • Wolf Rayet 134, 





    
        

            Jonathan W MacCollum
    B
  • Wolf Rayet 134, 





    
        

            Jonathan W MacCollum
    C
  • Final
    Wolf Rayet 134, 





    
        

            Jonathan W MacCollum
    D

B

Starless

C

Oiii Data - Starless

D

Complete re-process of superluminance and recombination using HOO blend (no RGB stars) R=Ha G=50% Ha / 50% Oiii B=Oiii Included gentle HDR Transformation and Local Histogram Equalization on luminance

Sky plot

Sky plot

Histogram

Wolf Rayet 134, 





    
        

            Jonathan W MacCollum